target sdk 35

Used separate threads for reading and writing, enhancing concurrency and performance.

Note: before was possible to start `SerialInputOutputManager` with `Executors.newSingleThreadExecutor().submit(ioManager)`. Now you have to use `ioManager.start()`

.github/workflows/build.yml

@@ -8,10 +8,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v1
-    - name: set up JDK 1.8
-      uses: actions/setup-java@v1
+    - uses: actions/checkout@v3
+    - uses: actions/setup-java@v3
       with:
-        java-version: 1.8
+        distribution: 'temurin'
+        java-version: '17'
     - name: Build with Gradle
       run: ./gradlew assembleDebug

.gitignore

@@ -40,4 +40,4 @@ build/
 local.properties
 *.DS_Store
 proguard/
-
+jacoco.exec

.idea/.gitignore

@@ -2,3 +2,8 @@ caches
 codeStyles
 libraries
 workspace.xml
+androidTestResultsUserPreferences.xml
+appInsightsSettings.xml
+deploymentTargetDropDown.xml
+deploymentTargetSelector.xml
+other.xml

.idea/AndroidProjectSystem.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AndroidProjectSystem">
+    <option name="providerId" value="com.android.tools.idea.GradleProjectSystem" />
+  </component>
+</project>

.idea/compiler.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CompilerConfiguration">
+    <bytecodeTargetLevel target="21" />
+  </component>
+</project>

.idea/misc.xml

@@ -1,11 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="NullableNotNullManager">
-    <option name="myDefaultNullable" value="android.support.annotation.Nullable" />
-    <option name="myDefaultNotNull" value="android.support.annotation.NonNull" />
+    <option name="myDefaultNullable" value="androidx.annotation.Nullable" />
+    <option name="myDefaultNotNull" value="androidx.annotation.NonNull" />
     <option name="myNullables">
       <value>
-        <list size="12">
+        <list size="18">
           <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.Nullable" />
           <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nullable" />
           <item index="2" class="java.lang.String" itemvalue="javax.annotation.CheckForNull" />
@@ -18,12 +19,18 @@
           <item index="9" class="java.lang.String" itemvalue="org.checkerframework.checker.nullness.compatqual.NullableDecl" />
           <item index="10" class="java.lang.String" itemvalue="org.checkerframework.checker.nullness.compatqual.NullableType" />
           <item index="11" class="java.lang.String" itemvalue="com.android.annotations.Nullable" />
+          <item index="12" class="java.lang.String" itemvalue="org.eclipse.jdt.annotation.Nullable" />
+          <item index="13" class="java.lang.String" itemvalue="io.reactivex.annotations.Nullable" />
+          <item index="14" class="java.lang.String" itemvalue="io.reactivex.rxjava3.annotations.Nullable" />
+          <item index="15" class="java.lang.String" itemvalue="org.jspecify.nullness.Nullable" />
+          <item index="16" class="java.lang.String" itemvalue="jakarta.annotation.Nullable" />
+          <item index="17" class="java.lang.String" itemvalue="org.jspecify.annotations.Nullable" />
         </list>
       </value>
     </option>
     <option name="myNotNulls">
       <value>
-        <list size="11">
+        <list size="17">
           <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.NotNull" />
           <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nonnull" />
           <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.NonNull" />
@@ -35,11 +42,17 @@
           <item index="8" class="java.lang.String" itemvalue="org.checkerframework.checker.nullness.compatqual.NonNullDecl" />
           <item index="9" class="java.lang.String" itemvalue="org.checkerframework.checker.nullness.compatqual.NonNullType" />
           <item index="10" class="java.lang.String" itemvalue="com.android.annotations.NonNull" />
+          <item index="11" class="java.lang.String" itemvalue="org.eclipse.jdt.annotation.NonNull" />
+          <item index="12" class="java.lang.String" itemvalue="io.reactivex.annotations.NonNull" />
+          <item index="13" class="java.lang.String" itemvalue="io.reactivex.rxjava3.annotations.NonNull" />
+          <item index="14" class="java.lang.String" itemvalue="jakarta.annotation.Nonnull" />
+          <item index="15" class="java.lang.String" itemvalue="org.jspecify.nullness.NonNull" />
+          <item index="16" class="java.lang.String" itemvalue="org.jspecify.annotations.NonNull" />
         </list>
       </value>
     </option>
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="jbr-21" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
   <component name="ProjectType">

.idea/modules.xml

@@ -1,10 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="ProjectModuleManager">
-    <modules>
-      <module fileurl="file://$PROJECT_DIR$/usb-serial-for-android.iml" filepath="$PROJECT_DIR$/usb-serial-for-android.iml" group="usb-serial-for-android" />
-      <module fileurl="file://$PROJECT_DIR$/usbSerialExamples/usbSerialExamples.iml" filepath="$PROJECT_DIR$/usbSerialExamples/usbSerialExamples.iml" group="usb-serial-for-android/usbSerialExamples" />
-      <module fileurl="file://$PROJECT_DIR$/usbSerialForAndroid/usbSerialForAndroid.iml" filepath="$PROJECT_DIR$/usbSerialForAndroid/usbSerialForAndroid.iml" group="usb-serial-for-android/usbSerialForAndroid" />
-    </modules>
-  </component>
-</project>

.idea/runConfigurations.xml

@@ -3,9 +3,14 @@
   <component name="RunConfigurationProducerService">
     <option name="ignoredProducers">
       <set>
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.AllInPackageGradleConfigurationProducer" />
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestClassGradleConfigurationProducer" />
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestMethodGradleConfigurationProducer" />
+        <option value="com.intellij.execution.junit.AbstractAllInDirectoryConfigurationProducer" />
+        <option value="com.intellij.execution.junit.AllInPackageConfigurationProducer" />
+        <option value="com.intellij.execution.junit.PatternConfigurationProducer" />
+        <option value="com.intellij.execution.junit.TestInClassConfigurationProducer" />
+        <option value="com.intellij.execution.junit.UniqueIdConfigurationProducer" />
+        <option value="com.intellij.execution.junit.testDiscovery.JUnitTestDiscoveryConfigurationProducer" />
+        <option value="org.jetbrains.kotlin.idea.junit.KotlinJUnitRunConfigurationProducer" />
+        <option value="org.jetbrains.kotlin.idea.junit.KotlinPatternConfigurationProducer" />
       </set>
     </option>
   </component>

README.md

@@ -1,6 +1,6 @@
 [![Actions Status](https://github.com/mik3y/usb-serial-for-android/workflows/build/badge.svg)](https://github.com/mik3y/usb-serial-for-android/actions)
 [![Jitpack](https://jitpack.io/v/mik3y/usb-serial-for-android.svg)](https://jitpack.io/#mik3y/usb-serial-for-android)
-[![Codacy](https://api.codacy.com/project/badge/Grade/4d528e82e35d42d49f659e9b93a9c77d)](https://www.codacy.com/manual/kai-morich/usb-serial-for-android-mik3y?utm_source=github.com&utm_medium=referral&utm_content=mik3y/usb-serial-for-android&utm_campaign=Badge_Grade)
+[![Codacy](https://app.codacy.com/project/badge/Grade/ef799bba8a7343818af0a90eba3ecb46)](https://app.codacy.com/gh/kai-morich/usb-serial-for-android-mik3y/dashboard?utm_source=gh&utm_medium=referral&utm_content=&utm_campaign=Badge_grade)
 [![codecov](https://codecov.io/gh/mik3y/usb-serial-for-android/branch/master/graph/badge.svg)](https://codecov.io/gh/mik3y/usb-serial-for-android)
 
 # usb-serial-for-android
@@ -11,8 +11,7 @@ Android, using the
 available since Android 3.1 and working reliably since Android 4.2.
 
 No root access, ADK, or special kernel drivers are required; all drivers are implemented in
-Java.  You get a raw serial port with `read()`, `write()`, and other basic
-functions for use with your own protocols.
+Java.  You get a raw serial port with `read()`, `write()`, and [other functions](https://github.com/mik3y/usb-serial-for-android/wiki/FAQ#Feature_Matrix) for use with your own protocols.
 
 ## Quick Start
 
@@ -27,10 +26,26 @@ allprojects {
     }
 }
 ```
+
+Starting with gradle 6.8 you can alternatively add jitpack.io repository to your settings.gradle:
+```gradle
+dependencyResolutionManagement {
+    repositories {
+        ...
+        maven { url 'https://jitpack.io' }
+    }
+}
+```
+
+If using gradle kotlin  use line
+```gradle.kts
+        maven(url = "https://jitpack.io")
+```
+
 Add library to dependencies
 ```gradle
 dependencies {
-    implementation 'com.github.mik3y:usb-serial-for-android:Tag'
+    implementation 'com.github.mik3y:usb-serial-for-android:3.9.0'
 }
 ```
 
@@ -82,7 +97,7 @@ then use direct read/write
 or direct write + event driven read:
 ```java
     usbIoManager = new SerialInputOutputManager(usbSerialPort, this);
-    Executors.newSingleThreadExecutor().submit(usbIoManager);
+    usbIoManager.start();
     ...
     port.write("hello".getBytes(), WRITE_WAIT_MILLIS);
     
@@ -100,9 +115,10 @@ For a simple example, see
 [UsbSerialExamples](https://github.com/mik3y/usb-serial-for-android/blob/master/usbSerialExamples)
 folder in this project.
 
-For a more complete example with background service to stay connected while
-the app is not visible or rotating, see separate github project 
-[SimpleUsbTerminal](https://github.com/kai-morich/SimpleUsbTerminal).
+See separate github project [SimpleUsbTerminal](https://github.com/kai-morich/SimpleUsbTerminal) 
+for a more complete example with:
+* Background service to stay connected while the app is not visible or rotating
+* Flow control 
 
 ## Probing for Unrecognized Devices
 
@@ -114,22 +130,23 @@ new device or for one using a custom VID/PID pair.
 UsbSerialProber is a class to help you find and instantiate compatible
 UsbSerialDrivers from the tree of connected UsbDevices.  Normally, you will use
 the default prober returned by ``UsbSerialProber.getDefaultProber()``, which
-uses the built-in list of well-known VIDs and PIDs that are supported by our
-drivers.
+uses USB interface types and the built-in list of well-known VIDs and PIDs that
+are supported by our drivers.
 
 To use your own set of rules, create and use a custom prober:
 
 ```java
-// Probe for our custom CDC devices, which use VID 0x1234
-// and PIDS 0x0001 and 0x0002.
+// Probe for our custom FTDI device, which use VID 0x1234 and PID 0x0001 and 0x0002.
 ProbeTable customTable = new ProbeTable();
-customTable.addProduct(0x1234, 0x0001, CdcAcmSerialDriver.class);
-customTable.addProduct(0x1234, 0x0002, CdcAcmSerialDriver.class);
+customTable.addProduct(0x1234, 0x0001, FtdiSerialDriver.class);
+customTable.addProduct(0x1234, 0x0002, FtdiSerialDriver.class);
 
 UsbSerialProber prober = new UsbSerialProber(customTable);
 List<UsbSerialDriver> drivers = prober.findAllDrivers(usbManager);
 // ...
 ```
+*Note*: as of v3.5.0 this library detects CDC/ACM devices by USB interface types instead of fixed VID+PID,
+so custom probers are typically not required any more for CDC/ACM devices.
 
 Of course, nothing requires you to use UsbSerialProber at all: you can
 instantiate driver classes directly if you know what you're doing; just supply
@@ -137,23 +154,26 @@ a compatible UsbDevice.
 
 ## Compatible Devices
 
-This library supports USB to serial converter chips:
+This library supports USB to serial converter chips with specific drivers
 * FTDI FT232R, FT232H, FT2232H, FT4232H, FT230X, FT231X, FT234XD
 * Prolific PL2303
-* Silabs CP2102, CP2105, ...
+* Silabs CP2102, CP210*
 * Qinheng CH340, CH341A
 
-and devices implementing the CDC/ACM protocol like
+some other device specific drivers
+* GsmModem devices, e.g. for Unisoc based Fibocom GSM modems
+* Chrome OS CCD (Closed Case Debugging)
+
+and devices implementing the generic CDC/ACM protocol like
+* Qinheng CH9102
+* Microchip MCP2221
 * Arduino using ATmega32U4
 * Digispark using V-USB software USB
-* BBC micro:bit using ARM mbed DAPLink firmware
 * ...
 
 ## Help & Discussion
 
-For common problems, see the
-[Troubleshooting](https://github.com/mik3y/usb-serial-for-android/wiki/Troubleshooting)
-wiki page.
+For common problems, see the [FAQ](https://github.com/mik3y/usb-serial-for-android/wiki/FAQ) wiki page.
 
 Are you using the library? Add your project to 
 [ProjectsUsingUsbSerialForAndroid](https://github.com/mik3y/usb-serial-for-android/wiki/Projects-Using-usb-serial-for-android).

build.gradle

@@ -2,17 +2,17 @@
 
 buildscript {
     repositories {
-        jcenter()
+        mavenCentral()
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.0.1'
+        classpath 'com.android.tools.build:gradle:8.9.1'
     }
 }
 
 allprojects {
     repositories {
-        jcenter()
+        mavenCentral()
         google()
     }
 }

codecov.yml

@@ -0,0 +1,5 @@
+codecov:
+  max_report_age: off
+  require_ci_to_pass: no
+  notify:
+    wait_for_ci: no

gradle.properties

@@ -1,2 +1,3 @@
-#android.enableJetifier=true
+android.enableJetifier=true
 android.useAndroidX=true
+android.defaults.buildfeatures.buildconfig=true

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Wed Jun 10 08:41:47 CEST 2020
+#Tue Oct 13 21:20:09 CEST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-all.zip

jitpack.yml

@@ -0,0 +1,4 @@
+jdk:
+  - openjdk17
+install:
+  - ./gradlew :usbSerialForAndroid:publishToMavenLocal

test/pi_pico/README.md

@@ -0,0 +1,6 @@
+
+# `tinyusb_dev_cdc_dual_ports.uf2`
+
+compiled from `C:/Program Files/Raspberry Pi/Pico SDK v1.5.1/pico-sdk/lib/tinyusb/examples/device/cdc_dual_ports`
+to `C:/Users/` _user_`/Documents/Pico-v1.5.1/pico-examples/build/usb/device/tinyusb_device_examples/cdc_dual_ports/tinyusb_dev_cdc_dual_ports.uf2`
+

usbSerialExamples/build.gradle

@@ -1,8 +1,9 @@
-apply plugin: 'com.android.application'
+plugins {
+    id 'com.android.application'
+}
 
 android {
-    compileSdkVersion 29
-    buildToolsVersion '29.0.3'
+    compileSdkVersion 35
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -11,10 +12,9 @@ android {
 
     defaultConfig {
         minSdkVersion 17
-        targetSdkVersion 28
+        targetSdkVersion 35
         vectorDrawables.useSupportLibrary = true
 
-        testInstrumentationRunner "android.test.InstrumentationTestRunner"
         missingDimensionStrategy 'device', 'anyDevice'
     }
 
@@ -23,10 +23,11 @@ android {
             minifyEnabled true
         }
     }
+    namespace 'com.hoho.android.usbserial.examples'
 }
 
 dependencies {
     implementation project(':usbSerialForAndroid')
-    implementation 'androidx.appcompat:appcompat:1.1.0'
-    implementation 'com.google.android.material:material:1.1.0'
+    implementation 'androidx.appcompat:appcompat:1.6.1' // later versions have minsdk 21
+    implementation 'com.google.android.material:material:1.11.0' // later versions have minsdk 19
 }

usbSerialExamples/src/main/AndroidManifest.xml

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    package="com.hoho.android.usbserial.examples">
+    xmlns:tools="http://schemas.android.com/tools">
 
     <!-- mipmap/ic_launcher created with Android Studio -> New -> Image Asset using @color/colorPrimary and USB clip art -->
     <application
@@ -15,9 +14,9 @@
              when the settings activity is currently shown -->
         <activity
             android:name=".MainActivity"
-            android:label="@string/app_name"
             android:launchMode="singleTask"
-            android:windowSoftInputMode="stateHidden|adjustResize">
+            android:windowSoftInputMode="stateHidden|adjustResize"
+            android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />

usbSerialExamples/src/main/java/com/hoho/android/usbserial/examples/CustomProber.java

@@ -1,6 +1,6 @@
 package com.hoho.android.usbserial.examples;
 
-import com.hoho.android.usbserial.driver.CdcAcmSerialDriver;
+import com.hoho.android.usbserial.driver.FtdiSerialDriver;
 import com.hoho.android.usbserial.driver.ProbeTable;
 import com.hoho.android.usbserial.driver.UsbSerialProber;
 
@@ -14,7 +14,8 @@ class CustomProber {
 
     static UsbSerialProber getCustomProber() {
         ProbeTable customTable = new ProbeTable();
-        customTable.addProduct(0x16d0, 0x087e, CdcAcmSerialDriver.class); // e.g. Digispark CDC
+        customTable.addProduct(0x1234, 0x0001, FtdiSerialDriver.class); // e.g. device with custom VID+PID
+        customTable.addProduct(0x1234, 0x0002, FtdiSerialDriver.class); // e.g. device with custom VID+PID
         return new UsbSerialProber(customTable);
     }
 

usbSerialExamples/src/main/java/com/hoho/android/usbserial/examples/DevicesFragment.java

@@ -5,6 +5,8 @@ import android.content.Context;
 import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbManager;
 import android.os.Bundle;
+
+import androidx.annotation.NonNull;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.ListFragment;
 import android.view.Menu;
@@ -25,7 +27,7 @@ import java.util.Locale;
 
 public class DevicesFragment extends ListFragment {
 
-    class ListItem {
+    static class ListItem {
         UsbDevice device;
         int port;
         UsbSerialDriver driver;
@@ -37,7 +39,7 @@ public class DevicesFragment extends ListFragment {
         }
     }
 
-    private ArrayList<ListItem> listItems = new ArrayList<>();
+    private final ArrayList<ListItem> listItems = new ArrayList<>();
     private ArrayAdapter<ListItem> listAdapter;
     private int baudRate = 19200;
     private boolean withIoManager = true;
@@ -47,8 +49,9 @@ public class DevicesFragment extends ListFragment {
         super.onCreate(savedInstanceState);
         setHasOptionsMenu(true);
         listAdapter = new ArrayAdapter<ListItem>(getActivity(), 0, listItems) {
+            @NonNull
             @Override
-            public View getView(int position, View view, ViewGroup parent) {
+            public View getView(int position, View view, @NonNull ViewGroup parent) {
                 ListItem item = listItems.get(position);
                 if (view == null)
                     view = getActivity().getLayoutInflater().inflate(R.layout.device_list_item, parent, false);
@@ -78,7 +81,7 @@ public class DevicesFragment extends ListFragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, MenuInflater inflater) {
         inflater.inflate(R.menu.menu_devices, menu);
     }
 
@@ -142,7 +145,7 @@ public class DevicesFragment extends ListFragment {
     }
 
     @Override
-    public void onListItemClick(ListView l, View v, int position, long id) {
+    public void onListItemClick(@NonNull ListView l, @NonNull View v, int position, long id) {
         ListItem item = listItems.get(position-1);
         if(item.driver == null) {
             Toast.makeText(getActivity(), "no driver", Toast.LENGTH_SHORT).show();

usbSerialExamples/src/main/java/com/hoho/android/usbserial/examples/MainActivity.java

@@ -34,7 +34,7 @@ public class MainActivity extends AppCompatActivity implements FragmentManager.O
 
     @Override
     protected void onNewIntent(Intent intent) {
-        if(intent.getAction().equals("android.hardware.usb.action.USB_DEVICE_ATTACHED")) {
+        if("android.hardware.usb.action.USB_DEVICE_ATTACHED".equals(intent.getAction())) {
             TerminalFragment terminal = (TerminalFragment)getSupportFragmentManager().findFragmentByTag("terminal");
             if (terminal != null)
                 terminal.status("USB device detected");

usbSerialExamples/src/main/java/com/hoho/android/usbserial/examples/TerminalFragment.java

@@ -8,6 +8,7 @@ import android.content.IntentFilter;
 import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbManager;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Looper;
@@ -27,6 +28,7 @@ import android.widget.ToggleButton;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.content.ContextCompat;
 import androidx.fragment.app.Fragment;
 
 import com.hoho.android.usbserial.driver.UsbSerialDriver;
@@ -38,11 +40,10 @@ import com.hoho.android.usbserial.util.SerialInputOutputManager;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.EnumSet;
-import java.util.concurrent.Executors;
 
 public class TerminalFragment extends Fragment implements SerialInputOutputManager.Listener {
 
-    private enum UsbPermission { Unknown, Requested, Granted, Denied };
+    private enum UsbPermission { Unknown, Requested, Granted, Denied }
 
     private static final String INTENT_ACTION_GRANT_USB = BuildConfig.APPLICATION_ID + ".GRANT_USB";
     private static final int WRITE_WAIT_MILLIS = 2000;
@@ -51,8 +52,8 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
     private int deviceId, portNum, baudRate;
     private boolean withIoManager;
 
-    private BroadcastReceiver broadcastReceiver;
-    private Handler mainLooper;
+    private final BroadcastReceiver broadcastReceiver;
+    private final Handler mainLooper;
     private TextView receiveText;
     private ControlLines controlLines;
 
@@ -65,7 +66,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         broadcastReceiver = new BroadcastReceiver() {
             @Override
             public void onReceive(Context context, Intent intent) {
-                if(intent.getAction().equals(INTENT_ACTION_GRANT_USB)) {
+                if(INTENT_ACTION_GRANT_USB.equals(intent.getAction())) {
                     usbPermission = intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)
                             ? UsbPermission.Granted : UsbPermission.Denied;
                     connect();
@@ -89,12 +90,22 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         withIoManager = getArguments().getBoolean("withIoManager");
     }
 
+    @Override
+    public void onStart() {
+        super.onStart();
+        ContextCompat.registerReceiver(getActivity(), broadcastReceiver, new IntentFilter(INTENT_ACTION_GRANT_USB), ContextCompat.RECEIVER_NOT_EXPORTED);
+    }
+
+    @Override
+    public void onStop() {
+        getActivity().unregisterReceiver(broadcastReceiver);
+        super.onStop();
+    }
+
     @Override
     public void onResume() {
         super.onResume();
-        getActivity().registerReceiver(broadcastReceiver, new IntentFilter(INTENT_ACTION_GRANT_USB));
-
-        if(usbPermission == UsbPermission.Unknown || usbPermission == UsbPermission.Granted)
+        if(!connected && (usbPermission == UsbPermission.Unknown || usbPermission == UsbPermission.Granted))
             mainLooper.post(this::connect);
     }
 
@@ -104,7 +115,6 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
             status("disconnected");
             disconnect();
         }
-        getActivity().unregisterReceiver(broadcastReceiver);
         super.onPause();
     }
 
@@ -141,6 +151,25 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         if (id == R.id.clear) {
             receiveText.setText("");
             return true;
+        } else if( id == R.id.send_break) {
+            if(!connected) {
+                Toast.makeText(getActivity(), "not connected", Toast.LENGTH_SHORT).show();
+            } else {
+                try {
+                    usbSerialPort.setBreak(true);
+                    Thread.sleep(100); // should show progress bar instead of blocking UI thread
+                    usbSerialPort.setBreak(false);
+                    SpannableStringBuilder spn = new SpannableStringBuilder();
+                    spn.append("send <break>\n");
+                    spn.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.colorSendText)), 0, spn.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
+                    receiveText.append(spn);
+                } catch(UnsupportedOperationException ignored) {
+                    Toast.makeText(getActivity(), "BREAK not supported", Toast.LENGTH_SHORT).show();
+                } catch(Exception e) {
+                    Toast.makeText(getActivity(), "BREAK failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
+                }
+            }
+            return true;
         } else {
             return super.onOptionsItemSelected(item);
         }
@@ -185,7 +214,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
             status("connection failed: no driver for device");
             return;
         }
-        if(driver.getPorts().size() < portNum) {
+        if(portNum >= driver.getPorts().size()) {
             status("connection failed: not enough ports at device");
             return;
         }
@@ -193,7 +222,10 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         UsbDeviceConnection usbConnection = usbManager.openDevice(driver.getDevice());
         if(usbConnection == null && usbPermission == UsbPermission.Unknown && !usbManager.hasPermission(driver.getDevice())) {
             usbPermission = UsbPermission.Requested;
-            PendingIntent usbPermissionIntent = PendingIntent.getBroadcast(getActivity(), 0, new Intent(INTENT_ACTION_GRANT_USB), 0);
+            int flags = Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ? PendingIntent.FLAG_MUTABLE : 0;
+            Intent intent = new Intent(INTENT_ACTION_GRANT_USB);
+            intent.setPackage(getActivity().getPackageName());
+            PendingIntent usbPermissionIntent = PendingIntent.getBroadcast(getActivity(), 0, intent, flags);
             usbManager.requestPermission(driver.getDevice(), usbPermissionIntent);
             return;
         }
@@ -207,10 +239,14 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
 
         try {
             usbSerialPort.open(usbConnection);
-            usbSerialPort.setParameters(baudRate, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);
+            try{
+                usbSerialPort.setParameters(baudRate, 8, 1, UsbSerialPort.PARITY_NONE);
+            }catch (UnsupportedOperationException e){
+                status("unsupport setparameters");
+            }
             if(withIoManager) {
                 usbIoManager = new SerialInputOutputManager(usbSerialPort, this);
-                Executors.newSingleThreadExecutor().submit(usbIoManager);
+                usbIoManager.start();
             }
             status("connected");
             connected = true;
@@ -224,8 +260,10 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
     private void disconnect() {
         connected = false;
         controlLines.stop();
-        if(usbIoManager != null)
+        if(usbIoManager != null) {
+            usbIoManager.setListener(null);
             usbIoManager.stop();
+        }
         usbIoManager = null;
         try {
             usbSerialPort.close();
@@ -239,10 +277,10 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
             return;
         }
         try {
-            byte[] data = (str + '\n').getBytes();
+        byte[] data = (str + '\n').getBytes();
             SpannableStringBuilder spn = new SpannableStringBuilder();
             spn.append("send " + data.length + " bytes\n");
-            spn.append(HexDump.dumpHexString(data)+"\n");
+            spn.append(HexDump.dumpHexString(data)).append("\n");
             spn.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.colorSendText)), 0, spn.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
             receiveText.append(spn);
             usbSerialPort.write(data, WRITE_WAIT_MILLIS);
@@ -272,7 +310,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         SpannableStringBuilder spn = new SpannableStringBuilder();
         spn.append("receive " + data.length + " bytes\n");
         if(data.length > 0)
-            spn.append(HexDump.dumpHexString(data)+"\n");
+            spn.append(HexDump.dumpHexString(data)).append("\n");
         receiveText.append(spn);
     }
 
@@ -285,8 +323,8 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
     class ControlLines {
         private static final int refreshInterval = 200; // msec
 
-        private Runnable runnable;
-        private ToggleButton rtsBtn, ctsBtn, dtrBtn, dsrBtn, cdBtn, riBtn;
+        private final Runnable runnable;
+        private final ToggleButton rtsBtn, ctsBtn, dtrBtn, dsrBtn, cdBtn, riBtn;
 
         ControlLines(View view) {
             runnable = this::run; // w/o explicit Runnable, a new lambda would be created on each postDelayed, which would not be found again by removeCallbacks
@@ -329,7 +367,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
                 cdBtn.setChecked(controlLines.contains(UsbSerialPort.ControlLine.CD));
                 riBtn.setChecked(controlLines.contains(UsbSerialPort.ControlLine.RI));
                 mainLooper.postDelayed(runnable, refreshInterval);
-            } catch (IOException e) {
+            } catch (Exception e) {
                 status("getControlLines() failed: " + e.getMessage() + " -> stopped control line refresh");
             }
         }
@@ -346,8 +384,15 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
                 if (!controlLines.contains(UsbSerialPort.ControlLine.CD))   cdBtn.setVisibility(View.INVISIBLE);
                 if (!controlLines.contains(UsbSerialPort.ControlLine.RI))   riBtn.setVisibility(View.INVISIBLE);
                 run();
-            } catch (IOException e) {
+            } catch (Exception e) {
                 Toast.makeText(getActivity(), "getSupportedControlLines() failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
+                rtsBtn.setVisibility(View.INVISIBLE);
+                ctsBtn.setVisibility(View.INVISIBLE);
+                dtrBtn.setVisibility(View.INVISIBLE);
+                dsrBtn.setVisibility(View.INVISIBLE);
+                cdBtn.setVisibility(View.INVISIBLE);
+                cdBtn.setVisibility(View.INVISIBLE);
+                riBtn.setVisibility(View.INVISIBLE);
             }
         }
 

usbSerialExamples/src/main/res/menu/menu_terminal.xml

@@ -6,4 +6,8 @@
         android:icon="@drawable/ic_delete_white_24dp"
         android:title="Clear"
         app:showAsAction="always" />
+    <item
+        android:id="@+id/send_break"
+        android:title="Send BREAK"
+        app:showAsAction="never" />
 </menu>

usbSerialExamples/src/main/res/xml/device_filter.xml

@@ -8,13 +8,18 @@
     <usb-device vendor-id="1027" product-id="24597" /> <!-- 0x6015: FT230X, FT231X, FT234XD -->
 
     <!-- 0x10C4 / 0xEA??: Silabs CP210x -->
-    <usb-device vendor-id="4292" product-id="60000" /> <!-- 0xea60: CP2102 -->
+    <usb-device vendor-id="4292" product-id="60000" /> <!-- 0xea60: CP2102 and other CP210x single port devices -->
     <usb-device vendor-id="4292" product-id="60016" /> <!-- 0xea70: CP2105 -->
     <usb-device vendor-id="4292" product-id="60017" /> <!-- 0xea71: CP2108 -->
-    <usb-device vendor-id="4292" product-id="60032" /> <!-- 0xea80: CP2110 -->
 
-    <!-- 0x067B / 0x2303: Prolific PL2303 -->
-    <usb-device vendor-id="1659" product-id="8963" />
+    <!-- 0x067B / 0x23?3: Prolific PL2303x -->
+    <usb-device vendor-id="1659" product-id="8963" /> <!-- 0x2303: PL2303HX, HXD, TA, ... -->
+    <usb-device vendor-id="1659" product-id="9123" /> <!-- 0x23a3: PL2303GC -->
+    <usb-device vendor-id="1659" product-id="9139" /> <!-- 0x23b3: PL2303GB -->
+    <usb-device vendor-id="1659" product-id="9155" /> <!-- 0x23c3: PL2303GT -->
+    <usb-device vendor-id="1659" product-id="9171" /> <!-- 0x23d3: PL2303GL -->
+    <usb-device vendor-id="1659" product-id="9187" /> <!-- 0x23e3: PL2303GE -->
+    <usb-device vendor-id="1659" product-id="9203" /> <!-- 0x23f3: PL2303GS -->
 
     <!-- 0x1a86 / 0x?523: Qinheng CH34x -->
     <usb-device vendor-id="6790" product-id="21795" /> <!-- 0x5523: CH341A -->
@@ -26,4 +31,8 @@
     <usb-device vendor-id="1003" product-id="8260" /> <!-- 0x03EB / 0x2044: Atmel Lufa -->
     <usb-device vendor-id="7855" product-id="4"    /> <!-- 0x1eaf / 0x0004: Leaflabs Maple -->
     <usb-device vendor-id="3368" product-id="516"  /> <!-- 0x0d28 / 0x0204: ARM mbed -->
+    <usb-device vendor-id="1155" product-id="22336" /><!-- 0x0483 / 0x5740: ST CDC -->
+    <usb-device vendor-id="11914" product-id="5"   /> <!-- 0x2E8A / 0x0005: Raspberry Pi Pico Micropython -->
+    <usb-device vendor-id="11914" product-id="10"  /> <!-- 0x2E8A / 0x000A: Raspberry Pi Pico SDK -->
+    <usb-device vendor-id="6790" product-id="21972" /><!-- 0x1A86 / 0x55D4: Qinheng CH9102F -->
 </resources>

usbSerialForAndroid/build.gradle

@@ -1,17 +1,19 @@
-apply plugin: 'com.android.library'
+plugins {
+    id 'com.android.library'
+    id 'maven-publish'
+}
 
 android {
-    compileSdkVersion 29
-    buildToolsVersion '29.0.3'
+    compileSdkVersion 35
 
     defaultConfig {
         minSdkVersion 17
-        targetSdkVersion 28
+        targetSdkVersion 35
         consumerProguardFiles 'proguard-rules.pro'
         
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         testInstrumentationRunnerArguments = [                    // Raspi   Windows   LinuxVM   ...
-                'rfc2217_server_host': '192.168.0.100',
+                'rfc2217_server_host': '192.168.0.78',
                 'rfc2217_server_nonstandard_baudrates': 'true',   // true    false     false
         ]
     }
@@ -19,16 +21,40 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+    namespace 'com.hoho.android.usbserial'
+    publishing {
+        // if coverage is enabled, change 'release' to 'anyDeviceRelease' or comment out publishing rule
+        singleVariant('release') {
+            withSourcesJar()
+        }
+    }
 }
 
 dependencies {
-    testImplementation 'junit:junit:4.13'
-    androidTestImplementation 'com.android.support:support-annotations:28.0.0'
-    androidTestImplementation 'com.android.support.test:runner:1.0.2'
-    androidTestImplementation 'commons-net:commons-net:3.6'
-    androidTestImplementation 'org.apache.commons:commons-lang3:3.8.1' // starting with 3.9 requires min-api 26
+    implementation "androidx.annotation:annotation:1.9.1"
+    testImplementation 'junit:junit:4.13.2'
+    testImplementation 'org.mockito:mockito-core:5.15.2'
+    androidTestImplementation 'androidx.appcompat:appcompat:1.6.1' // later versions have minsdk 21
+    androidTestImplementation 'androidx.test:core:1.5.0' // later versions have minsdk 19
+    androidTestImplementation 'androidx.test:runner:1.5.2' // later versions have minsdk 19
+    androidTestImplementation 'commons-net:commons-net:3.9.0' // later versions fail on old Android devices with missing java.time.Duration class
+    androidTestImplementation 'org.apache.commons:commons-lang3:3.14.0'
 }
 
-//apply from: 'publishToMavenLocal.gradle'
+// gradle task: publishToMavenLocal
+project.afterEvaluate {
+    publishing {
+        publications {
+            release(MavenPublication) {
+                from components.release
+
+                // values used for local maven repo, jitpack uses github release:
+                groupId 'com.github.mik3y'
+                artifactId 'usb-serial-for-android'
+                version '3.8.0beta'
+            }
+        }
+    }
+}
 
 //apply from: 'coverage.gradle'

usbSerialForAndroid/coverage.gradle

@@ -1,13 +1,14 @@
+// see https://github.com/mik3y/usb-serial-for-android/wiki/Device-Tests-&-Coverage-Report for instructions
 apply plugin: 'jacoco'
 
 android {
-    flavorDimensions 'device'
+    flavorDimensions += 'device'
     productFlavors {
         anyDevice {
             // Used as fallback in usbSerialExample/build.gradle -> missingDimensionStrategy, but not for coverage report
             dimension 'device'
         }
-        arduino {
+        mcp2221 {
             dimension 'device'
             testInstrumentationRunnerArguments = ['test_device_driver': 'CdcAcm']
         }
@@ -17,7 +18,7 @@ android {
         }
         cp2102 { // and cp2105 first port
             dimension 'device'
-            testInstrumentationRunnerArguments = ['test_device_driver': 'Cp21xx']
+            testInstrumentationRunnerArguments = ['test_device_driver': 'Cp21xx', 'test_device_port': '0']
         }
         cp2105 { // second port
             dimension 'device'
@@ -25,13 +26,21 @@ android {
         }
         ft232 { // and ft2232 first port
             dimension 'device'
-            testInstrumentationRunnerArguments = ['test_device_driver': 'Ftdi']
+            testInstrumentationRunnerArguments = ['test_device_driver': 'Ftdi', 'test_device_port': '0']
         }
         ft2232 { // second port
             dimension 'device'
             testInstrumentationRunnerArguments = ['test_device_driver': 'Ftdi', 'test_device_port': '1']
         }
-        pl2302 {
+        pl2303 {
+            dimension 'device'
+            testInstrumentationRunnerArguments = ['test_device_driver': 'Prolific']
+        }
+        pl2303t {
+            dimension 'device'
+            testInstrumentationRunnerArguments = ['test_device_driver': 'Prolific']
+        }
+        pl2303g {
             dimension 'device'
             testInstrumentationRunnerArguments = ['test_device_driver': 'Prolific']
         }
@@ -39,13 +48,31 @@ android {
 
     buildTypes {
         debug {
-            testCoverageEnabled true
+            enableUnitTestCoverage true
+            enableAndroidTestCoverage true
         }
     }
 }
+
 // create report even if tests fail
 project.gradle.taskGraph.whenReady {
     -> project.tasks.findAll { it.name =~ /connected.+AndroidTest/ }.each {
         it.ignoreFailures = true
     }
 }
+
+task jacocoTestReport(type: JacocoReport, dependsOn: ['compileAnyDeviceDebugSources'
+                                                  /*, 'testAnyDeviceDebugUnitTest' */
+                                                  /*, 'create<device>DebugCoverageReport' */]) {
+    def fileFilter = ['**/R.class', '**/R$*.class', '**/BuildConfig.*', '**/Manifest*.*', '**/*Test*.*', 'android/**/*.*']
+    def debugTree = fileTree(dir: "$project.buildDir/intermediates/javac/anyDeviceDebug", excludes: fileFilter)
+    def mainSrc = "$project.projectDir/src/main/java"
+
+    reports.xml.required = true
+    sourceDirectories.from files([mainSrc])
+    classDirectories.from files([debugTree])
+    executionData.from fileTree(dir: project.buildDir, includes: [
+            'outputs/unit_test_code_coverage/anyDeviceDebugUnitTest/testAnyDeviceDebugUnitTest.exec',
+            'outputs/code_coverage/*DebugAndroidTest/connected/*/coverage.ec'
+    ])
+}

usbSerialForAndroid/publishToMavenLocal.gradle

@@ -1,20 +0,0 @@
-apply plugin: 'maven-publish'
-
-publishing {
-    publications {
-        maven(MavenPublication) {
-            groupId 'com.github.mik3y'
-            artifactId 'usb-serial-for-android'
-            version '3.0.0beta'
-            afterEvaluate {
-                artifact androidSourcesJar
-                artifact bundleReleaseAar
-            }
-        }
-    }
-}
-
-task androidSourcesJar(type: Jar) {
-    classifier 'sources'
-    from android.sourceSets.main.java.srcDirs
-}

usbSerialForAndroid/src/androidTest/AndroidManifest.xml

@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-      package="com.hoho.android.usbserial"
       android:versionCode="1"
       android:versionName="1.0">
     <uses-permission android:name="android.permission.INTERNET"/>

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/CrossoverTest.java

@@ -7,13 +7,15 @@ package com.hoho.android.usbserial;
 
 import android.content.Context;
 import android.hardware.usb.UsbManager;
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.platform.app.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
 import android.util.Log;
 
 import com.hoho.android.usbserial.driver.UsbSerialDriver;
 import com.hoho.android.usbserial.driver.UsbSerialPort;
 import com.hoho.android.usbserial.driver.UsbSerialProber;
+import com.hoho.android.usbserial.util.TestBuffer;
 import com.hoho.android.usbserial.util.UsbWrapper;
 
 import org.junit.Before;
@@ -24,12 +26,14 @@ import org.junit.rules.TestWatcher;
 import org.junit.runner.Description;
 import org.junit.runner.RunWith;
 
+import java.io.IOException;
 import java.util.EnumSet;
 import java.util.List;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeTrue;
@@ -55,19 +59,19 @@ public class CrossoverTest {
         assumeTrue("ignore test for device specific coverage report",
                 InstrumentationRegistry.getArguments().getString("test_device_driver") == null);
 
-        context = InstrumentationRegistry.getContext();
+        context = ApplicationProvider.getApplicationContext();
         usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
         List<UsbSerialDriver> availableDrivers = UsbSerialProber.getDefaultProber().findAllDrivers(usbManager);
         assertNotEquals("no USB device found", 0, availableDrivers.size());
         if (availableDrivers.size() == 0) {
             fail("no USB device found");
         } else if (availableDrivers.size() == 1) {
-            assertEquals(2, availableDrivers.get(0).getPorts().size());
+            assertEquals("expected device with 2 ports.", 2, availableDrivers.get(0).getPorts().size());
             usb1 = new UsbWrapper(context, availableDrivers.get(0), 0);
             usb2 = new UsbWrapper(context, availableDrivers.get(0), 1);
         } else {
-            assertEquals(1, availableDrivers.get(0).getPorts().size());
-            assertEquals(1, availableDrivers.get(1).getPorts().size());
+            assertEquals("expected 2 devices with 1 port.", 1, availableDrivers.get(0).getPorts().size());
+            assertEquals("expected 2 devices with 1 port.", 1, availableDrivers.get(1).getPorts().size());
             usb1 = new UsbWrapper(context, availableDrivers.get(0), 0);
             usb2 = new UsbWrapper(context, availableDrivers.get(1), 0);
         }
@@ -160,4 +164,53 @@ public class CrossoverTest {
         usb2.close();
     }
 
+    @Test
+    public void concurrent() throws Exception {
+        // 115200 baud ~= 11kB/sec => ~1.5 second test duration with 16kB tbuf
+        // concurrent (+ blocking) write calls as tbuf larger than any buffer size returned by UsbWrapper.getWriteSizes()
+        // concurrent read calls in IoManager threads
+        TestBuffer tbuf1 = new TestBuffer(16*1024);
+        TestBuffer tbuf2 = new TestBuffer(16*1024);
+
+        class WriteRunnable implements Runnable {
+            public WriteRunnable(int port) { this.port = port; }
+            private final int port;
+            Exception exc;
+            @Override
+            public void run() {
+                byte[] buf = new byte[1024];
+                try {
+                    for(int i=0; i<tbuf1.buf.length / 1024; i++) {
+                        System.arraycopy(tbuf1.buf, i*1024, buf, 0, 1024);
+                        if (port == 1)
+                            usb1.write(buf);
+                        else
+                            usb2.write(buf);
+                    }
+                } catch (IOException exc) {
+                    this.exc = exc;
+                }
+            }
+        }
+
+        usb1.open();
+        usb2.open();
+        usb1.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
+        usb2.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
+        WriteRunnable wr1 = new WriteRunnable(1), wr2 = new WriteRunnable(2);
+        Thread wt1 = new Thread(wr1), wt2 = new Thread(wr2);
+        boolean done1 = false, done2 = false;
+        wt1.start();
+        Thread.sleep(50);
+        wt2.start();
+        while(!done1 && !done2) {
+            if(!done1)
+                done1 = tbuf1.testRead(usb1.read(-1));
+            if(!done2)
+                done2 = tbuf2.testRead(usb2.read(-1));
+        }
+        wt1.join(); wt2.join();
+        assertNull(wr1.exc);
+        assertNull(wr2.exc);
+    }
 }

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/driver/CommonUsbSerialPortWrapper.java

@@ -0,0 +1,8 @@
+package com.hoho.android.usbserial.driver;
+
+public class CommonUsbSerialPortWrapper {
+    public static byte[] getWriteBuffer(UsbSerialPort serialPort) {
+        CommonUsbSerialPort commonSerialPort = (CommonUsbSerialPort) serialPort;
+        return commonSerialPort.mWriteBuffer;
+    }
+}

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/driver/ProlificSerialPortWrapper.java

@@ -0,0 +1,13 @@
+package com.hoho.android.usbserial.driver;
+
+public class ProlificSerialPortWrapper {
+    public static boolean isDeviceTypeT(UsbSerialPort serialPort) {
+        ProlificSerialDriver.ProlificSerialPort prolificSerialPort = (ProlificSerialDriver.ProlificSerialPort) serialPort;
+        return prolificSerialPort.mDeviceType == ProlificSerialDriver.DeviceType.DEVICE_TYPE_T;
+    }
+
+    public static boolean isDeviceTypeHxn(UsbSerialPort serialPort) {
+        ProlificSerialDriver.ProlificSerialPort prolificSerialPort = (ProlificSerialDriver.ProlificSerialPort) serialPort;
+        return prolificSerialPort.mDeviceType == ProlificSerialDriver.DeviceType.DEVICE_TYPE_HXN;
+    }
+}

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/util/TelnetWrapper.java

@@ -1,5 +1,7 @@
 package com.hoho.android.usbserial.util;
 
+import com.hoho.android.usbserial.driver.UsbSerialPort;
+
 import org.apache.commons.net.telnet.InvalidTelnetOptionException;
 import org.apache.commons.net.telnet.TelnetClient;
 import org.apache.commons.net.telnet.TelnetCommand;
@@ -9,6 +11,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
+import java.util.ArrayList;
 
 import static org.junit.Assert.assertEquals;
 
@@ -31,7 +34,7 @@ public class TelnetWrapper {
     private TelnetClient telnetClient;
     private InputStream readStream;
     private OutputStream writeStream;
-    private Integer[] comPortOptionCounter = {0};
+    private ArrayList<int[]> commandResponse = new ArrayList<>();
     public int writeDelay = 0;
 
     public TelnetWrapper(String host, int port) {
@@ -47,7 +50,9 @@ public class TelnetWrapper {
         telnetClient.addOptionHandler(new TelnetOptionHandler(RFC2217_COM_PORT_OPTION, false, false, false, false) {
             @Override
             public int[] answerSubnegotiation(int[] suboptionData, int suboptionLength) {
-                comPortOptionCounter[0] += 1;
+                int[] data = new int[suboptionLength];
+                System.arraycopy(suboptionData, 0, data, 0, suboptionLength);
+                commandResponse.add(data);
                 return super.answerSubnegotiation(suboptionData, suboptionLength);
             }
         });
@@ -59,18 +64,25 @@ public class TelnetWrapper {
         readStream = telnetClient.getInputStream();
     }
 
+    private int[] doCommand(String name, byte[] command) throws IOException, InterruptedException {
+        commandResponse.clear();
+        telnetClient.sendCommand((byte) TelnetCommand.SB);
+        writeStream.write(command);
+        telnetClient.sendCommand((byte)TelnetCommand.SE);
+
+        for(int i=0; i<TELNET_COMMAND_WAIT; i++) {
+            if(commandResponse.size() > 0) break;
+            Thread.sleep(1);
+        }
+        assertEquals("RFC2217 " + name+ " w/o response.", 1, commandResponse.size());
+        //Log.d(TAG, name + " -> " + Arrays.toString(commandResponse.get(0)));
+        return commandResponse.get(0);
+    }
+
     public void setUp() throws Exception {
         setUpFixtureInt();
         telnetClient.sendAYT(1000); // not correctly handled by rfc2217_server.py, but WARNING output "ignoring Telnet command: '\xf6'" is a nice separator between tests
-        comPortOptionCounter[0] = 0;
-        telnetClient.sendCommand((byte)TelnetCommand.SB);
-        writeStream.write(new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_PURGE_DATA, 3});
-        telnetClient.sendCommand((byte)TelnetCommand.SE);
-        for(int i=0; i<TELNET_COMMAND_WAIT; i++) {
-            if(comPortOptionCounter[0] == 1) break;
-            Thread.sleep(1);
-        }
-        assertEquals("telnet connection lost", 1, comPortOptionCounter[0].intValue());
+        doCommand("purge-data", new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_PURGE_DATA, 3});
         writeDelay = 0;
     }
 
@@ -92,11 +104,15 @@ public class TelnetWrapper {
 
     // wait full time
     public byte[] read() throws Exception {
-        return read(-1);
+        return read(-1, -1);
     }
-
     public byte[] read(int expectedLength) throws Exception {
-        long end = System.currentTimeMillis() + TELNET_READ_WAIT;
+        return read(expectedLength, -1);
+    }
+    public byte[] read(int expectedLength, int readWait) throws Exception {
+        if(readWait == -1)
+            readWait = TELNET_READ_WAIT;
+        long end = System.currentTimeMillis() + readWait;
         ByteBuffer buf = ByteBuffer.allocate(65536);
         while(System.currentTimeMillis() < end) {
             if(readStream.available() > 0) {
@@ -126,30 +142,11 @@ public class TelnetWrapper {
         }
     }
 
-    public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException, InterruptedException, InvalidTelnetOptionException {
-        comPortOptionCounter[0] = 0;
-
-        telnetClient.sendCommand((byte) TelnetCommand.SB);
-        writeStream.write(new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_BAUDRATE, (byte)(baudRate>>24), (byte)(baudRate>>16), (byte)(baudRate>>8), (byte)baudRate});
-        telnetClient.sendCommand((byte)TelnetCommand.SE);
-
-        telnetClient.sendCommand((byte)TelnetCommand.SB);
-        writeStream.write(new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_DATASIZE, (byte)dataBits});
-        telnetClient.sendCommand((byte)TelnetCommand.SE);
-
-        telnetClient.sendCommand((byte)TelnetCommand.SB);
-        writeStream.write(new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_STOPSIZE, (byte)stopBits});
-        telnetClient.sendCommand((byte)TelnetCommand.SE);
-
-        telnetClient.sendCommand((byte)TelnetCommand.SB);
-        writeStream.write(new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_PARITY, (byte)(parity+1)});
-        telnetClient.sendCommand((byte)TelnetCommand.SE);
-
-        // windows does not like nonstandard baudrates. rfc2217_server.py terminates w/o response
-        for(int i=0; i<TELNET_COMMAND_WAIT; i++) {
-            if(comPortOptionCounter[0] == 4) break;
-            Thread.sleep(1);
-        }
-        assertEquals("telnet connection lost", 4, comPortOptionCounter[0].intValue());
+    public void setParameters(int baudRate, int dataBits, int stopBits, @UsbSerialPort.Parity int parity) throws IOException, InterruptedException, InvalidTelnetOptionException {
+        doCommand("set-baudrate", new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_BAUDRATE, (byte)(baudRate>>24), (byte)(baudRate>>16), (byte)(baudRate>>8), (byte)baudRate});
+        doCommand("set-datasize", new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_DATASIZE, (byte)dataBits});
+        doCommand("set-stopsize", new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_STOPSIZE, (byte)stopBits});
+        doCommand("set-parity", new byte[] {RFC2217_COM_PORT_OPTION, RFC2217_SET_PARITY, (byte)(parity+1)});
     }
+
 }

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/util/TestBuffer.java

@@ -0,0 +1,32 @@
+package com.hoho.android.usbserial.util;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+public class TestBuffer {
+    public final byte[] buf;
+    public int len;
+
+    public TestBuffer(int length) {
+        len = 0;
+        buf = new byte[length];
+        int i = 0;
+        int j = 0;
+        for (j = 0; j < length / 16; j++)
+            for (int k = 0; k < 16; k++)
+                buf[i++] = (byte) j;
+        while (i < length)
+            buf[i++] = (byte) j;
+    }
+
+    public boolean testRead(byte[] data) {
+        assertNotEquals(0, data.length);
+        assertTrue("got " + (len + data.length) + " bytes", (len + data.length) <= buf.length);
+        for (int j = 0; j < data.length; j++)
+            assertEquals("at pos " + (len + j), (byte) ((len + j) / 16), data[j]);
+        len += data.length;
+        //Log.d(TAG, "read " + len);
+        return len == buf.length;
+    }
+}

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/util/UsbWrapper.java

@@ -5,13 +5,21 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
-import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbManager;
-import android.os.Process;
+import android.media.RingtoneManager;
+import android.net.Uri;
+import android.os.Build;
 import android.util.Log;
 
 import com.hoho.android.usbserial.driver.CdcAcmSerialDriver;
+import com.hoho.android.usbserial.driver.Ch34xSerialDriver;
+import com.hoho.android.usbserial.driver.CommonUsbSerialPort;
+import com.hoho.android.usbserial.driver.Cp21xxSerialDriver;
+import com.hoho.android.usbserial.driver.FtdiSerialDriver;
+import com.hoho.android.usbserial.driver.ProlificSerialDriver;
+import com.hoho.android.usbserial.driver.ProlificSerialPortWrapper;
+import com.hoho.android.usbserial.driver.UsbId;
 import com.hoho.android.usbserial.driver.UsbSerialDriver;
 import com.hoho.android.usbserial.driver.UsbSerialPort;
 
@@ -21,24 +29,19 @@ import java.util.Deque;
 import java.util.EnumSet;
 import java.util.LinkedList;
 import java.util.concurrent.Callable;
-import java.util.concurrent.Executors;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotEquals;
-import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
 
+import androidx.core.content.ContextCompat;
 
 public class UsbWrapper implements SerialInputOutputManager.Listener {
 
-    private final static int     USB_READ_WAIT = 500;
-    private final static int     USB_WRITE_WAIT = 500;
-    private final static Integer SERIAL_INPUT_OUTPUT_MANAGER_THREAD_PRIORITY = Process.THREAD_PRIORITY_URGENT_AUDIO;
+    public final static int     USB_READ_WAIT = 500;
+    public final static int     USB_WRITE_WAIT = 500;
     private static final String TAG = UsbWrapper.class.getSimpleName();
 
-    public enum OpenCloseFlags { NO_IOMANAGER_THREAD, NO_CONTROL_LINE_INIT, NO_DEVICE_CONNECTION };
+    public enum OpenCloseFlags { NO_IOMANAGER_THREAD, NO_IOMANAGER_START, NO_CONTROL_LINE_INIT, NO_DEVICE_CONNECTION };
 
     // constructor
     final Context context;
@@ -54,17 +57,30 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
     public boolean readBlock = false;
     long readTime = 0;
 
+    // device properties
+    public boolean isCp21xxRestrictedPort; // second port of Cp2105 has limited dataBits, stopBits, parity
+    public boolean outputLinesSupported;
+    public boolean inputLinesSupported;
+    public boolean inputLinesConnected;
+    public boolean inputLinesOnlyRtsCts;
+    public int writePacketSize = -1;
+    public int writeBufferSize = -1;
+    public int readBufferSize = -1;
 
     public UsbWrapper(Context context, UsbSerialDriver serialDriver, int devicePort) {
         this.context = context;
         this.serialDriver = serialDriver;
         this.devicePort = devicePort;
         serialPort = serialDriver.getPorts().get(devicePort);
+        CommonUsbSerialPort.DEBUG = true;
     }
 
     public void setUp() throws Exception {
         UsbManager usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
         if (!usbManager.hasPermission(serialDriver.getDevice())) {
+            Uri notification = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
+            RingtoneManager.getRingtone(context, notification).play();
+
             Log.d(TAG,"USB permission ...");
             final Boolean[] granted = {null};
             BroadcastReceiver usbReceiver = new BroadcastReceiver() {
@@ -73,17 +89,78 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
                     granted[0] = intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false);
                 }
             };
-            PendingIntent permissionIntent = PendingIntent.getBroadcast(context, 0, new Intent("com.android.example.USB_PERMISSION"), 0);
+            int flags = Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ? PendingIntent.FLAG_MUTABLE : 0;
+            Intent intent = new Intent("com.android.example.USB_PERMISSION");
+            intent.setPackage(context.getPackageName());
+            PendingIntent permissionIntent = PendingIntent.getBroadcast(context, 0, intent, flags);
             IntentFilter filter = new IntentFilter("com.android.example.USB_PERMISSION");
-            context.registerReceiver(usbReceiver, filter);
+            ContextCompat.registerReceiver(context, usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED);
             usbManager.requestPermission(serialDriver.getDevice(), permissionIntent);
             for(int i=0; i<5000; i++) {
                 if(granted[0] != null) break;
                 Thread.sleep(1);
             }
             Log.d(TAG,"USB permission "+granted[0]);
-            assertTrue("USB permission dialog not confirmed", granted[0]==null?false:granted[0]);
+            assertTrue("USB permission dialog not confirmed", granted[0] != null && granted[0]);
         }
+
+        // extract some device properties:
+        isCp21xxRestrictedPort = serialDriver instanceof Cp21xxSerialDriver && serialDriver.getPorts().size()==2 && serialPort.getPortNumber() == 1;
+        // output lines are supported by all common drivers
+        // input lines are supported by all common drivers except CDC
+        if (serialDriver instanceof FtdiSerialDriver) {
+            outputLinesSupported = true;
+            inputLinesSupported = true;
+            if(serialDriver.getDevice().getProductId() == UsbId.FTDI_FT2232H)
+                inputLinesConnected = true; // I only have 74LS138 connected at FT2232, not at FT232
+            if(serialDriver.getDevice().getProductId() == UsbId.FTDI_FT231X) {
+                inputLinesConnected = true;
+                inputLinesOnlyRtsCts = true; // I only test with FT230X that has only these 2 control lines. DTR is silently ignored
+            }
+        } else if (serialDriver instanceof Cp21xxSerialDriver) {
+            outputLinesSupported = true;
+            inputLinesSupported = true;
+            if(serialDriver.getPorts().size() == 1)
+                inputLinesConnected = true; // I only have 74LS138 connected at CP2102, not at CP2105
+        } else if (serialDriver instanceof ProlificSerialDriver) {
+            outputLinesSupported = true;
+            inputLinesSupported = true;
+            inputLinesConnected = true;
+        } else if (serialDriver instanceof Ch34xSerialDriver) {
+            outputLinesSupported = true;
+            inputLinesSupported = true;
+            if(serialDriver.getDevice().getProductId() == UsbId.QINHENG_CH340)
+                inputLinesConnected = true;  // I only have 74LS138 connected at CH340, not connected at CH341A
+        } else if (serialDriver instanceof CdcAcmSerialDriver) {
+            outputLinesSupported = true;
+        }
+
+        if (serialDriver instanceof Cp21xxSerialDriver) {
+            if (serialDriver.getPorts().size() == 1) { writePacketSize = 64; writeBufferSize = 576; }
+            else if (serialPort.getPortNumber() == 0) { writePacketSize = 64; writeBufferSize = 320; }
+            else { writePacketSize = 32; writeBufferSize = 128; }; //, 160}; // write buffer size detection is unreliable
+        } else if (serialDriver instanceof Ch34xSerialDriver) {
+            writePacketSize = 32; writeBufferSize = 64;
+        } else if (serialDriver instanceof ProlificSerialDriver) {
+            writePacketSize = 64; writeBufferSize = 256;
+        } else if (serialDriver instanceof FtdiSerialDriver) {
+            switch (serialDriver.getPorts().size()) {
+                case 1: writePacketSize = 64; writeBufferSize = 128; break;
+                case 2: writePacketSize = 512; writeBufferSize = 4096; break;
+                case 4: writePacketSize = 512; writeBufferSize = 2048; break;
+            }
+            if(serialDriver.getDevice().getProductId() == UsbId.FTDI_FT231X)
+                writeBufferSize = 512;
+        } else if (serialDriver instanceof CdcAcmSerialDriver) {
+            writePacketSize = 16; writeBufferSize = 32; // MCP2221 values, other devices might be different
+        }
+
+        readBufferSize = writeBufferSize;
+        if (serialDriver instanceof Cp21xxSerialDriver && serialDriver.getPorts().size() == 2) {
+            readBufferSize = 256;
+        } else if (serialDriver instanceof FtdiSerialDriver && serialDriver.getPorts().size() == 1 && serialDriver.getDevice().getProductId() != UsbId.FTDI_FT231X) {
+            readBufferSize = 256;
+        } // PL2303 HXN checked in open()
     }
 
     public void tearDown() {
@@ -112,6 +189,8 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
                 if(!flags.contains(OpenCloseFlags.NO_CONTROL_LINE_INIT)) {
                     serialPort.setDTR(false);
                     serialPort.setRTS(false);
+                    if (serialPort.getFlowControl() != UsbSerialPort.FlowControl.NONE)
+                        serialPort.setFlowControl(UsbSerialPort.FlowControl.NONE);
                 }
             } catch (Exception ignored) {
             }
@@ -139,14 +218,10 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
     }
 
     public void open() throws Exception {
-        open(EnumSet.noneOf(OpenCloseFlags.class), 0);
+        open(EnumSet.noneOf(OpenCloseFlags.class));
     }
 
     public void open(EnumSet<OpenCloseFlags> flags) throws Exception {
-        open(flags, 0);
-    }
-
-    public void open(EnumSet<OpenCloseFlags> flags, int ioManagerTimeout) throws Exception {
         if(!flags.contains(OpenCloseFlags.NO_DEVICE_CONNECTION)) {
             UsbManager usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
             deviceConnection = usbManager.openDevice(serialDriver.getDevice());
@@ -157,36 +232,62 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
             serialPort.setRTS(true);
         }
         if(!flags.contains(OpenCloseFlags.NO_IOMANAGER_THREAD)) {
-            ioManager = new SerialInputOutputManager(serialPort, this) {
-                @Override
-                public void run() {
-                    if (SERIAL_INPUT_OUTPUT_MANAGER_THREAD_PRIORITY != null)
-                        Process.setThreadPriority(SERIAL_INPUT_OUTPUT_MANAGER_THREAD_PRIORITY);
-                    super.run();
-                }
-            };
-            ioManager.setReadTimeout(ioManagerTimeout);
-            ioManager.setWriteTimeout(ioManagerTimeout);
-            Executors.newSingleThreadExecutor().submit(ioManager);
+            ioManager = new SerialInputOutputManager(serialPort, this);
+            if(!flags.contains(OpenCloseFlags.NO_IOMANAGER_START))
+                ioManager.start();
         }
         synchronized (readBuffer) {
             readBuffer.clear();
         }
         readError = null;
+
+        if (serialDriver instanceof ProlificSerialDriver && ProlificSerialPortWrapper.isDeviceTypeHxn(serialPort)) {
+            readBufferSize = 768;
+        }
+    }
+
+    public void waitForIoManagerStarted() throws IOException {
+        for (int i = 0; i < 100; i++) {
+            if (SerialInputOutputManager.State.STOPPED != ioManager.getState()) return;
+            try {
+                Thread.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+        throw new IOException("IoManager not started");
+    }
+
+    public boolean hasIoManagerThreads() {
+        int c = 0;
+        for (Thread thread : Thread.getAllStackTraces().keySet()) {
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_read"))
+                c += 1;
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_write"))
+                c += 1;
+        }
+        return c == 2;
     }
 
     // wait full time
     public byte[] read() throws Exception {
-        return read(-1);
+        return read(-1, -1, -1);
     }
-
     public byte[] read(int expectedLength) throws Exception {
-        long end = System.currentTimeMillis() + USB_READ_WAIT;
+        return read(expectedLength, -1, -1);
+    }
+    public byte[] read(int expectedLength, int readBufferSize) throws Exception {
+        return read(expectedLength, readBufferSize, -1);
+    }
+    public byte[] read(int expectedLength, int readBufferSize, int readWait) throws Exception {
+        if(readWait == -1)
+            readWait = USB_READ_WAIT;
+        long end = System.currentTimeMillis() + readWait;
         ByteBuffer buf = ByteBuffer.allocate(16*1024);
         if(ioManager != null) {
             while (System.currentTimeMillis() < end) {
                 if(readError != null)
-                    throw readError;
+                    throw new IOException(readError);
                 synchronized (readBuffer) {
                     while(readBuffer.peek() != null)
                         buf.put(readBuffer.remove());
@@ -197,7 +298,7 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
             }
 
         } else {
-            byte[] b1 = new byte[256];
+            byte[] b1 = new byte[readBufferSize > 0 ? readBufferSize : 256];
             while (System.currentTimeMillis() < end) {
                 int len = serialPort.read(b1, USB_READ_WAIT);
                 if (len > 0)
@@ -216,7 +317,7 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
         serialPort.write(data, USB_WRITE_WAIT);
     }
 
-    public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException, InterruptedException {
+    public void setParameters(int baudRate, int dataBits, int stopBits, @UsbSerialPort.Parity int parity) throws IOException, InterruptedException {
         serialPort.setParameters(baudRate, dataBits, stopBits, parity);
         if(serialDriver instanceof CdcAcmSerialDriver)
             Thread.sleep(10); // arduino_leonardeo_bridge.ini needs some time
@@ -233,15 +334,40 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
         }
     }
 
+    // return [write packet size, write buffer size(s)]
+    public int[] getWriteSizes() {
+        if (serialDriver instanceof Cp21xxSerialDriver) {
+            if (serialDriver.getPorts().size() == 1) return new int[]{64, 576};
+            else if (serialPort.getPortNumber() == 0) return new int[]{64, 320};
+            else return new int[]{32, 128, 160}; // write buffer size detection is unreliable
+        } else if (serialDriver instanceof Ch34xSerialDriver) {
+            return new int[]{32, 64};
+        } else if (serialDriver instanceof ProlificSerialDriver) {
+            return new int[]{64, 256};
+        } else if (serialDriver instanceof FtdiSerialDriver) {
+            switch (serialDriver.getPorts().size()) {
+                case 1: return new int[]{64, 128};
+                case 2: return new int[]{512, 4096};
+                case 4: return new int[]{512, 2048};
+                default: return null;
+            }
+        } else if (serialDriver instanceof CdcAcmSerialDriver) {
+            return new int[]{64, 128};
+        } else {
+            return null;
+        }
+    }
+
+
     @Override
     public void onNewData(byte[] data) {
         long now = System.currentTimeMillis();
         if(readTime == 0)
             readTime = now;
         if(data.length > 64) {
-            Log.d(TAG, "usb read: time+=" + String.format("%-3d",now- readTime) + " len=" + String.format("%-4d",data.length) + " data=" + new String(data, 0, 32) + "..." + new String(data, data.length-32, 32));
+            Log.d(TAG, "usb " + devicePort + " read: time+=" + String.format("%-3d",now- readTime) + " len=" + String.format("%-4d",data.length) + " data=" + new String(data, 0, 32) + "..." + new String(data, data.length-32, 32));
         } else {
-            Log.d(TAG, "usb read: time+=" + String.format("%-3d",now- readTime) + " len=" + String.format("%-4d",data.length) + " data=" + new String(data));
+            Log.d(TAG, "usb " + devicePort + " read: time+=" + String.format("%-3d",now- readTime) + " len=" + String.format("%-4d",data.length) + " data=" + new String(data));
         }
         readTime = now;
 

usbSerialForAndroid/src/main/AndroidManifest.xml

@@ -1,4 +1,3 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-      package="com.hoho.android.usbserial">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
 </manifest>

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CdcAcmSerialDriver.java

@@ -8,11 +8,13 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDevice;
-import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbInterface;
 import android.util.Log;
 
+import com.hoho.android.usbserial.util.HexDump;
+import com.hoho.android.usbserial.util.UsbUtils;
+
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.EnumSet;
@@ -30,6 +32,8 @@ import java.util.Map;
  */
 public class CdcAcmSerialDriver implements UsbSerialDriver {
 
+    public static final int USB_SUBCLASS_ACM = 2;
+
     private final String TAG = CdcAcmSerialDriver.class.getSimpleName();
 
     private final UsbDevice mDevice;
@@ -38,23 +42,33 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
     public CdcAcmSerialDriver(UsbDevice device) {
         mDevice = device;
         mPorts = new ArrayList<>();
-
-        int controlInterfaceCount = 0;
-        int dataInterfaceCount = 0;
-        for( int i = 0; i < device.getInterfaceCount(); i++) {
-            if(device.getInterface(i).getInterfaceClass() == UsbConstants.USB_CLASS_COMM)
-                controlInterfaceCount++;
-            if(device.getInterface(i).getInterfaceClass() == UsbConstants.USB_CLASS_CDC_DATA)
-                dataInterfaceCount++;
-        }
-        for( int port = 0; port < Math.min(controlInterfaceCount, dataInterfaceCount); port++) {
+        int ports = countPorts(device);
+        for (int port = 0; port < ports; port++) {
             mPorts.add(new CdcAcmSerialPort(mDevice, port));
         }
-        if(mPorts.size() == 0) {
+        if (mPorts.size() == 0) {
             mPorts.add(new CdcAcmSerialPort(mDevice, -1));
         }
     }
 
+    @SuppressWarnings({"unused"})
+    public static boolean probe(UsbDevice device) {
+        return countPorts(device) > 0;
+    }
+
+    private static int countPorts(UsbDevice device) {
+        int controlInterfaceCount = 0;
+        int dataInterfaceCount = 0;
+        for (int i = 0; i < device.getInterfaceCount(); i++) {
+            if (device.getInterface(i).getInterfaceClass() == UsbConstants.USB_CLASS_COMM &&
+                    device.getInterface(i).getInterfaceSubclass() == USB_SUBCLASS_ACM)
+                controlInterfaceCount++;
+            if (device.getInterface(i).getInterfaceClass() == UsbConstants.USB_CLASS_CDC_DATA)
+                dataInterfaceCount++;
+        }
+        return Math.min(controlInterfaceCount, dataInterfaceCount);
+    }
+
     @Override
     public UsbDevice getDevice() {
         return mDevice;
@@ -95,7 +109,11 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        protected void openInt(UsbDeviceConnection connection) throws IOException {
+        protected void openInt() throws IOException {
+            Log.d(TAG, "interfaces:");
+            for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
+                Log.d(TAG, mDevice.getInterface(i).toString());
+            }
             if (mPortNumber == -1) {
                 Log.d(TAG,"device might be castrated ACM device, trying single interface logic");
                 openSingleInterface();
@@ -131,38 +149,57 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
         }
 
         private void openInterface() throws IOException {
-            Log.d(TAG, "claiming interfaces, count=" + mDevice.getInterfaceCount());
 
-            int controlInterfaceCount = 0;
-            int dataInterfaceCount = 0;
             mControlInterface = null;
             mDataInterface = null;
-            for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
-                UsbInterface usbInterface = mDevice.getInterface(i);
-                if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_COMM) {
-                    if(controlInterfaceCount == mPortNumber) {
-                        mControlIndex = i;
-                        mControlInterface = usbInterface;
+            int j = getInterfaceIdFromDescriptors();
+            Log.d(TAG, "interface count=" + mDevice.getInterfaceCount() + ", IAD=" + j);
+            if (j >= 0) {
+                for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
+                    UsbInterface usbInterface = mDevice.getInterface(i);
+                    if (usbInterface.getId() == j || usbInterface.getId() == j+1) {
+                        if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_COMM &&
+                                usbInterface.getInterfaceSubclass() == USB_SUBCLASS_ACM) {
+                            mControlIndex = usbInterface.getId();
+                            mControlInterface = usbInterface;
+                        }
+                        if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_CDC_DATA) {
+                            mDataInterface = usbInterface;
+                        }
                     }
-                    controlInterfaceCount++;
                 }
-                if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_CDC_DATA) {
-                    if(dataInterfaceCount == mPortNumber) {
-                        mDataInterface = usbInterface;
+            }
+            if (mControlInterface == null || mDataInterface == null) {
+                Log.d(TAG, "no IAD fallback");
+                int controlInterfaceCount = 0;
+                int dataInterfaceCount = 0;
+                for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
+                    UsbInterface usbInterface = mDevice.getInterface(i);
+                    if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_COMM &&
+                            usbInterface.getInterfaceSubclass() == USB_SUBCLASS_ACM) {
+                        if (controlInterfaceCount == mPortNumber) {
+                            mControlIndex = usbInterface.getId();
+                            mControlInterface = usbInterface;
+                        }
+                        controlInterfaceCount++;
+                    }
+                    if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_CDC_DATA) {
+                        if (dataInterfaceCount == mPortNumber) {
+                            mDataInterface = usbInterface;
+                        }
+                        dataInterfaceCount++;
                     }
-                    dataInterfaceCount++;
                 }
             }
 
             if(mControlInterface == null) {
                 throw new IOException("No control interface");
             }
-            Log.d(TAG, "Control iface=" + mControlInterface);
+            Log.d(TAG, "Control interface id " + mControlInterface.getId());
 
             if (!mConnection.claimInterface(mControlInterface, true)) {
                 throw new IOException("Could not claim control interface");
             }
-
             mControlEndpoint = mControlInterface.getEndpoint(0);
             if (mControlEndpoint.getDirection() != UsbConstants.USB_DIR_IN || mControlEndpoint.getType() != UsbConstants.USB_ENDPOINT_XFER_INT) {
                 throw new IOException("Invalid control endpoint");
@@ -171,12 +208,10 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
             if(mDataInterface == null) {
                 throw new IOException("No data interface");
             }
-            Log.d(TAG, "data iface=" + mDataInterface);
-
+            Log.d(TAG, "data interface id " + mDataInterface.getId());
             if (!mConnection.claimInterface(mDataInterface, true)) {
                 throw new IOException("Could not claim data interface");
             }
-
             for (int i = 0; i < mDataInterface.getEndpointCount(); i++) {
                 UsbEndpoint ep = mDataInterface.getEndpoint(i);
                 if (ep.getDirection() == UsbConstants.USB_DIR_IN && ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)
@@ -186,6 +221,36 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
             }
         }
 
+        private int getInterfaceIdFromDescriptors() {
+            ArrayList<byte[]> descriptors = UsbUtils.getDescriptors(mConnection);
+            Log.d(TAG, "USB descriptor:");
+            for(byte[] descriptor : descriptors)
+                Log.d(TAG, HexDump.toHexString(descriptor));
+
+            if (descriptors.size() > 0 &&
+                    descriptors.get(0).length == 18 &&
+                    descriptors.get(0)[1] == 1 && // bDescriptorType
+                    descriptors.get(0)[4] == (byte)(UsbConstants.USB_CLASS_MISC) && //bDeviceClass
+                    descriptors.get(0)[5] == 2 && // bDeviceSubClass
+                    descriptors.get(0)[6] == 1) { // bDeviceProtocol
+                // is IAD device, see https://www.usb.org/sites/default/files/iadclasscode_r10.pdf
+                int port = -1;
+                for (int d = 1; d < descriptors.size(); d++) {
+                    if (descriptors.get(d).length == 8 &&
+                            descriptors.get(d)[1] == 0x0b && // bDescriptorType == IAD
+                            descriptors.get(d)[4] == UsbConstants.USB_CLASS_COMM && // bFunctionClass == CDC
+                            descriptors.get(d)[5] == USB_SUBCLASS_ACM) { // bFunctionSubClass == ACM
+                        port++;
+                        if (port == mPortNumber &&
+                                descriptors.get(d)[3] == 2) { // bInterfaceCount
+                            return descriptors.get(d)[2]; // bFirstInterface
+                        }
+                    }
+                }
+            }
+            return -1;
+        }
+
         private int sendAcmControlMessage(int request, int value, byte[] buf) throws IOException {
             int len = mConnection.controlTransfer(
                     USB_RT_ACM, request, value, mControlIndex, buf, buf != null ? buf.length : 0, 5000);
@@ -204,7 +269,7 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+        public void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException {
             if(baudRate <= 0) {
                 throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
             }
@@ -278,40 +343,17 @@ public class CdcAcmSerialDriver implements UsbSerialDriver {
         public EnumSet<ControlLine> getSupportedControlLines() throws IOException {
             return EnumSet.of(ControlLine.RTS, ControlLine.DTR);
         }
+
+        @Override
+        public void setBreak(boolean value) throws IOException {
+            sendAcmControlMessage(SEND_BREAK, value ? 0xffff : 0, null);
+        }
+
     }
 
+    @SuppressWarnings({"unused"})
     public static Map<Integer, int[]> getSupportedDevices() {
-        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<Integer, int[]>();
-        supportedDevices.put(UsbId.VENDOR_ARDUINO,
-                new int[] {
-                        UsbId.ARDUINO_UNO,
-                        UsbId.ARDUINO_UNO_R3,
-                        UsbId.ARDUINO_MEGA_2560,
-                        UsbId.ARDUINO_MEGA_2560_R3,
-                        UsbId.ARDUINO_SERIAL_ADAPTER,
-                        UsbId.ARDUINO_SERIAL_ADAPTER_R3,
-                        UsbId.ARDUINO_MEGA_ADK,
-                        UsbId.ARDUINO_MEGA_ADK_R3,
-                        UsbId.ARDUINO_LEONARDO,
-                        UsbId.ARDUINO_MICRO,
-                });
-        supportedDevices.put(UsbId.VENDOR_VAN_OOIJEN_TECH,
-                new int[] {
-                    UsbId.VAN_OOIJEN_TECH_TEENSYDUINO_SERIAL,
-                });
-        supportedDevices.put(UsbId.VENDOR_ATMEL,
-                new int[] {
-                    UsbId.ATMEL_LUFA_CDC_DEMO_APP,
-                });
-        supportedDevices.put(UsbId.VENDOR_LEAFLABS,
-                new int[] {
-                    UsbId.LEAFLABS_MAPLE,
-                });
-        supportedDevices.put(UsbId.VENDOR_ARM,
-                new int[] {
-                    UsbId.ARM_MBED,
-                });
-        return supportedDevices;
+        return new LinkedHashMap<>();
     }
 
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/Ch34xSerialDriver.java

@@ -7,9 +7,11 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDevice;
-import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbInterface;
+import android.util.Log;
+
+import com.hoho.android.usbserial.BuildConfig;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -20,336 +22,366 @@ import java.util.Map;
 
 public class Ch34xSerialDriver implements UsbSerialDriver {
 
-	private static final String TAG = Ch34xSerialDriver.class.getSimpleName();
+    private static final String TAG = Ch34xSerialDriver.class.getSimpleName();
 
-	private final UsbDevice mDevice;
-	private final UsbSerialPort mPort;
+    private final UsbDevice mDevice;
+    private final UsbSerialPort mPort;
 
-	private static final int LCR_ENABLE_RX   = 0x80;
-	private static final int LCR_ENABLE_TX   = 0x40;
-	private static final int LCR_MARK_SPACE  = 0x20;
-	private static final int LCR_PAR_EVEN    = 0x10;
-	private static final int LCR_ENABLE_PAR  = 0x08;
-	private static final int LCR_STOP_BITS_2 = 0x04;
-	private static final int LCR_CS8         = 0x03;
-	private static final int LCR_CS7         = 0x02;
-	private static final int LCR_CS6         = 0x01;
-	private static final int LCR_CS5         = 0x00;
+    private static final int LCR_ENABLE_RX   = 0x80;
+    private static final int LCR_ENABLE_TX   = 0x40;
+    private static final int LCR_MARK_SPACE  = 0x20;
+    private static final int LCR_PAR_EVEN    = 0x10;
+    private static final int LCR_ENABLE_PAR  = 0x08;
+    private static final int LCR_STOP_BITS_2 = 0x04;
+    private static final int LCR_CS8         = 0x03;
+    private static final int LCR_CS7         = 0x02;
+    private static final int LCR_CS6         = 0x01;
+    private static final int LCR_CS5         = 0x00;
 
-	private static final int GCL_CTS = 0x01;
-	private static final int GCL_DSR = 0x02;
-	private static final int GCL_RI  = 0x04;
-	private static final int GCL_CD  = 0x08;
-	private static final int SCL_DTR = 0x20;
-	private static final int SCL_RTS = 0x40;
+    private static final int GCL_CTS = 0x01;
+    private static final int GCL_DSR = 0x02;
+    private static final int GCL_RI  = 0x04;
+    private static final int GCL_CD  = 0x08;
+    private static final int SCL_DTR = 0x20;
+    private static final int SCL_RTS = 0x40;
 
-	public Ch34xSerialDriver(UsbDevice device) {
-		mDevice = device;
-		mPort = new Ch340SerialPort(mDevice, 0);
-	}
+    public Ch34xSerialDriver(UsbDevice device) {
+        mDevice = device;
+        mPort = new Ch340SerialPort(mDevice, 0);
+    }
 
-	@Override
-	public UsbDevice getDevice() {
-		return mDevice;
-	}
+    @Override
+    public UsbDevice getDevice() {
+        return mDevice;
+    }
 
-	@Override
-	public List<UsbSerialPort> getPorts() {
-		return Collections.singletonList(mPort);
-	}
+    @Override
+    public List<UsbSerialPort> getPorts() {
+        return Collections.singletonList(mPort);
+    }
 
-	public class Ch340SerialPort extends CommonUsbSerialPort {
+    public class Ch340SerialPort extends CommonUsbSerialPort {
 
-		private static final int USB_TIMEOUT_MILLIS = 5000;
+        private static final int USB_TIMEOUT_MILLIS = 5000;
 
-		private final int DEFAULT_BAUD_RATE = 9600;
+        private final int DEFAULT_BAUD_RATE = 9600;
 
-		private boolean dtr = false;
-		private boolean rts = false;
+        private boolean dtr = false;
+        private boolean rts = false;
 
-		public Ch340SerialPort(UsbDevice device, int portNumber) {
-			super(device, portNumber);
-		}
+        public Ch340SerialPort(UsbDevice device, int portNumber) {
+            super(device, portNumber);
+        }
 
-		@Override
-		public UsbSerialDriver getDriver() {
-			return Ch34xSerialDriver.this;
-		}
+        @Override
+        public UsbSerialDriver getDriver() {
+            return Ch34xSerialDriver.this;
+        }
 
-		@Override
-		protected void openInt(UsbDeviceConnection connection) throws IOException {
-			for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
-				UsbInterface usbIface = mDevice.getInterface(i);
-				if (!mConnection.claimInterface(usbIface, true)) {
-					throw new IOException("Could not claim data interface");
-				}
-			}
+        @Override
+        protected void openInt() throws IOException {
+            for (int i = 0; i < mDevice.getInterfaceCount(); i++) {
+                UsbInterface usbIface = mDevice.getInterface(i);
+                if (!mConnection.claimInterface(usbIface, true)) {
+                    throw new IOException("Could not claim data interface");
+                }
+            }
 
-			UsbInterface dataIface = mDevice.getInterface(mDevice.getInterfaceCount() - 1);
-			for (int i = 0; i < dataIface.getEndpointCount(); i++) {
-				UsbEndpoint ep = dataIface.getEndpoint(i);
-				if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
-					if (ep.getDirection() == UsbConstants.USB_DIR_IN) {
-						mReadEndpoint = ep;
-					} else {
-						mWriteEndpoint = ep;
-					}
-				}
-			}
+            UsbInterface dataIface = mDevice.getInterface(mDevice.getInterfaceCount() - 1);
+            for (int i = 0; i < dataIface.getEndpointCount(); i++) {
+                UsbEndpoint ep = dataIface.getEndpoint(i);
+                if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
+                    if (ep.getDirection() == UsbConstants.USB_DIR_IN) {
+                        mReadEndpoint = ep;
+                    } else {
+                        mWriteEndpoint = ep;
+                    }
+                }
+            }
 
-			initialize();
-			setBaudRate(DEFAULT_BAUD_RATE);
-		}
+            initialize();
+            setBaudRate(DEFAULT_BAUD_RATE);
+        }
 
-		@Override
-		protected void closeInt() {
-			try {
-				for (int i = 0; i < mDevice.getInterfaceCount(); i++)
-					mConnection.releaseInterface(mDevice.getInterface(i));
-			} catch(Exception ignored) {}
-		}
+        @Override
+        protected void closeInt() {
+            try {
+                for (int i = 0; i < mDevice.getInterfaceCount(); i++)
+                    mConnection.releaseInterface(mDevice.getInterface(i));
+            } catch(Exception ignored) {}
+        }
 
-		private int controlOut(int request, int value, int index) {
-			final int REQTYPE_HOST_TO_DEVICE = UsbConstants.USB_TYPE_VENDOR | UsbConstants.USB_DIR_OUT;
-			return mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, request,
-					value, index, null, 0, USB_TIMEOUT_MILLIS);
-		}
+        private int controlOut(int request, int value, int index) {
+            final int REQTYPE_HOST_TO_DEVICE = UsbConstants.USB_TYPE_VENDOR | UsbConstants.USB_DIR_OUT;
+            return mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, request,
+                    value, index, null, 0, USB_TIMEOUT_MILLIS);
+        }
 
 
-		private int controlIn(int request, int value, int index, byte[] buffer) {
-			final int REQTYPE_DEVICE_TO_HOST = UsbConstants.USB_TYPE_VENDOR | UsbConstants.USB_DIR_IN;
-			return mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, request,
-					value, index, buffer, buffer.length, USB_TIMEOUT_MILLIS);
-		}
+        private int controlIn(int request, int value, int index, byte[] buffer) {
+            final int REQTYPE_DEVICE_TO_HOST = UsbConstants.USB_TYPE_VENDOR | UsbConstants.USB_DIR_IN;
+            return mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, request,
+                    value, index, buffer, buffer.length, USB_TIMEOUT_MILLIS);
+        }
 
 
-		private void checkState(String msg, int request, int value, int[] expected) throws IOException {
-			byte[] buffer = new byte[expected.length];
-			int ret = controlIn(request, value, 0, buffer);
+        private void checkState(String msg, int request, int value, int[] expected) throws IOException {
+            byte[] buffer = new byte[expected.length];
+            int ret = controlIn(request, value, 0, buffer);
 
-			if (ret < 0) {
-				throw new IOException("Failed send cmd [" + msg + "]");
-			}
+            if (ret < 0) {
+                throw new IOException("Failed send cmd [" + msg + "]");
+            }
 
-			if (ret != expected.length) {
-				throw new IOException("Expected " + expected.length + " bytes, but get " + ret + " [" + msg + "]");
-			}
+            if (ret != expected.length) {
+                throw new IOException("Expected " + expected.length + " bytes, but get " + ret + " [" + msg + "]");
+            }
 
-			for (int i = 0; i < expected.length; i++) {
-				if (expected[i] == -1) {
-					continue;
-				}
+            for (int i = 0; i < expected.length; i++) {
+                if (expected[i] == -1) {
+                    continue;
+                }
 
-				int current = buffer[i] & 0xff;
-				if (expected[i] != current) {
-					throw new IOException("Expected 0x" + Integer.toHexString(expected[i]) + " byte, but get 0x" + Integer.toHexString(current) + " [" + msg + "]");
-				}
-			}
-		}
+                int current = buffer[i] & 0xff;
+                if (expected[i] != current) {
+                    throw new IOException("Expected 0x" + Integer.toHexString(expected[i]) + " byte, but get 0x" + Integer.toHexString(current) + " [" + msg + "]");
+                }
+            }
+        }
 
-		private void setControlLines() throws IOException {
-			if (controlOut(0xa4, ~((dtr ? SCL_DTR : 0) | (rts ? SCL_RTS : 0)), 0) < 0) {
-				throw new IOException("Failed to set control lines");
-			}
-		}
+        private void setControlLines() throws IOException {
+            if (controlOut(0xa4, ~((dtr ? SCL_DTR : 0) | (rts ? SCL_RTS : 0)), 0) < 0) {
+                throw new IOException("Failed to set control lines");
+            }
+        }
 
-		private byte getStatus() throws IOException {
-			byte[] buffer = new byte[2];
-			int ret = controlIn(0x95, 0x0706, 0, buffer);
-			if (ret < 0)
-				throw new IOException("Error getting control lines");
-			return buffer[0];
-		}
+        private byte getStatus() throws IOException {
+            byte[] buffer = new byte[2];
+            int ret = controlIn(0x95, 0x0706, 0, buffer);
+            if (ret < 0)
+                throw new IOException("Error getting control lines");
+            return buffer[0];
+        }
 
-		private void initialize() throws IOException {
-			checkState("init #1", 0x5f, 0, new int[]{-1 /* 0x27, 0x30 */, 0x00});
+        private void initialize() throws IOException {
+            checkState("init #1", 0x5f, 0, new int[]{-1 /* 0x27, 0x30 */, 0x00});
 
-			if (controlOut(0xa1, 0, 0) < 0) {
-				throw new IOException("Init failed: #2");
-			}
+            if (controlOut(0xa1, 0, 0) < 0) {
+                throw new IOException("Init failed: #2");
+            }
 
-			setBaudRate(DEFAULT_BAUD_RATE);
+            setBaudRate(DEFAULT_BAUD_RATE);
 
-			checkState("init #4", 0x95, 0x2518, new int[]{-1 /* 0x56, c3*/, 0x00});
+            checkState("init #4", 0x95, 0x2518, new int[]{-1 /* 0x56, c3*/, 0x00});
 
-			if (controlOut(0x9a, 0x2518, LCR_ENABLE_RX | LCR_ENABLE_TX | LCR_CS8) < 0) {
-				throw new IOException("Init failed: #5");
-			}
+            if (controlOut(0x9a, 0x2518, LCR_ENABLE_RX | LCR_ENABLE_TX | LCR_CS8) < 0) {
+                throw new IOException("Init failed: #5");
+            }
 
-			checkState("init #6", 0x95, 0x0706, new int[]{-1/*0xf?*/, -1/*0xec,0xee*/});
+            checkState("init #6", 0x95, 0x0706, new int[]{-1/*0xf?*/, -1/*0xec,0xee*/});
 
-			if (controlOut(0xa1, 0x501f, 0xd90a) < 0) {
-				throw new IOException("Init failed: #7");
-			}
+            if (controlOut(0xa1, 0x501f, 0xd90a) < 0) {
+                throw new IOException("Init failed: #7");
+            }
 
-			setBaudRate(DEFAULT_BAUD_RATE);
+            setBaudRate(DEFAULT_BAUD_RATE);
 
-			setControlLines();
+            setControlLines();
 
-			checkState("init #10", 0x95, 0x0706, new int[]{-1/* 0x9f, 0xff*/, -1/*0xec,0xee*/});
-		}
+            checkState("init #10", 0x95, 0x0706, new int[]{-1/* 0x9f, 0xff*/, -1/*0xec,0xee*/});
+        }
 
 
-		private void setBaudRate(int baudRate) throws IOException {
-			final long CH341_BAUDBASE_FACTOR = 1532620800;
-			final int CH341_BAUDBASE_DIVMAX = 3;
+        private void setBaudRate(int baudRate) throws IOException {
+            long factor;
+            long divisor;
 
-			long factor = CH341_BAUDBASE_FACTOR / baudRate;
-			int divisor = CH341_BAUDBASE_DIVMAX;
+            if (baudRate == 921600) {
+                divisor = 7;
+                factor = 0xf300;
+            } else {
+                final long BAUDBASE_FACTOR = 1532620800;
+                final int BAUDBASE_DIVMAX = 3;
 
-			while ((factor > 0xfff0) && divisor > 0) {
-				factor >>= 3;
-				divisor--;
-					}
+                if(BuildConfig.DEBUG && (baudRate & (3<<29)) == (1<<29))
+                    baudRate &= ~(1<<29); // for testing purpose bypass dedicated baud rate handling
+                factor = BAUDBASE_FACTOR / baudRate;
+                divisor = BAUDBASE_DIVMAX;
+                while ((factor > 0xfff0) && divisor > 0) {
+                    factor >>= 3;
+                    divisor--;
+                }
+                if (factor > 0xfff0) {
+                    throw new UnsupportedOperationException("Unsupported baud rate: " + baudRate);
+                }
+                factor = 0x10000 - factor;
+            }
 
-			if (factor > 0xfff0) {
-				throw new UnsupportedOperationException("Unsupported baud rate: " + baudRate);
-			}
+            divisor |= 0x0080; // else ch341a waits until buffer full
+            int val1 = (int) ((factor & 0xff00) | divisor);
+            int val2 = (int) (factor & 0xff);
+            Log.d(TAG, String.format("baud rate=%d, 0x1312=0x%04x, 0x0f2c=0x%04x", baudRate, val1, val2));
+            int ret = controlOut(0x9a, 0x1312, val1);
+            if (ret < 0) {
+                throw new IOException("Error setting baud rate: #1)");
+            }
+            ret = controlOut(0x9a, 0x0f2c, val2);
+            if (ret < 0) {
+                throw new IOException("Error setting baud rate: #2");
+            }
+        }
 
-			factor = 0x10000 - factor;
-			divisor |= 0x0080; // else ch341a waits until buffer full
-			int ret = controlOut(0x9a, 0x1312, (int) ((factor & 0xff00) | divisor));
-			if (ret < 0) {
-				throw new IOException("Error setting baud rate: #1)");
-			}
+        @Override
+        public void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException {
+            if(baudRate <= 0) {
+                throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
+            }
+            setBaudRate(baudRate);
 
-			ret = controlOut(0x9a, 0x0f2c, (int) (factor & 0xff));
-			if (ret < 0) {
-				throw new IOException("Error setting baud rate: #2");
-			}
-		}
+            int lcr = LCR_ENABLE_RX | LCR_ENABLE_TX;
 
-		@Override
-		public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
-			if(baudRate <= 0) {
-				throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
-			}
-			setBaudRate(baudRate);
+            switch (dataBits) {
+                case DATABITS_5:
+                    lcr |= LCR_CS5;
+                    break;
+                case DATABITS_6:
+                    lcr |= LCR_CS6;
+                    break;
+                case DATABITS_7:
+                    lcr |= LCR_CS7;
+                    break;
+                case DATABITS_8:
+                    lcr |= LCR_CS8;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Invalid data bits: " + dataBits);
+            }
 
-			int lcr = LCR_ENABLE_RX | LCR_ENABLE_TX;
+            switch (parity) {
+                case PARITY_NONE:
+                    break;
+                case PARITY_ODD:
+                    lcr |= LCR_ENABLE_PAR;
+                    break;
+                case PARITY_EVEN:
+                    lcr |= LCR_ENABLE_PAR | LCR_PAR_EVEN;
+                    break;
+                case PARITY_MARK:
+                    lcr |= LCR_ENABLE_PAR | LCR_MARK_SPACE;
+                    break;
+                case PARITY_SPACE:
+                    lcr |= LCR_ENABLE_PAR | LCR_MARK_SPACE | LCR_PAR_EVEN;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Invalid parity: " + parity);
+            }
 
-			switch (dataBits) {
-				case DATABITS_5:
-					lcr |= LCR_CS5;
-					break;
-				case DATABITS_6:
-					lcr |= LCR_CS6;
-					break;
-				case DATABITS_7:
-					lcr |= LCR_CS7;
-					break;
-				case DATABITS_8:
-					lcr |= LCR_CS8;
-					break;
-				default:
-					throw new IllegalArgumentException("Invalid data bits: " + dataBits);
-			}
+            switch (stopBits) {
+                case STOPBITS_1:
+                    break;
+                case STOPBITS_1_5:
+                    throw new UnsupportedOperationException("Unsupported stop bits: 1.5");
+                case STOPBITS_2:
+                    lcr |= LCR_STOP_BITS_2;
+                    break;
+                default:
+                    throw new IllegalArgumentException("Invalid stop bits: " + stopBits);
+            }
 
-			switch (parity) {
-				case PARITY_NONE:
-					break;
-				case PARITY_ODD:
-					lcr |= LCR_ENABLE_PAR;
-					break;
-				case PARITY_EVEN:
-					lcr |= LCR_ENABLE_PAR | LCR_PAR_EVEN;
-					break;
-				case PARITY_MARK:
-					lcr |= LCR_ENABLE_PAR | LCR_MARK_SPACE;
-					break;
-				case PARITY_SPACE:
-					lcr |= LCR_ENABLE_PAR | LCR_MARK_SPACE | LCR_PAR_EVEN;
-					break;
-				default:
-					throw new IllegalArgumentException("Invalid parity: " + parity);
-			}
+            int ret = controlOut(0x9a, 0x2518, lcr);
+            if (ret < 0) {
+                throw new IOException("Error setting control byte");
+            }
+        }
 
-			switch (stopBits) {
-				case STOPBITS_1:
-					break;
-				case STOPBITS_1_5:
-					throw new UnsupportedOperationException("Unsupported stop bits: 1.5");
-				case STOPBITS_2:
-					lcr |= LCR_STOP_BITS_2;
-					break;
-				default:
-					throw new IllegalArgumentException("Invalid stop bits: " + stopBits);
-			}
+        @Override
+        public boolean getCD() throws IOException {
+            return (getStatus() & GCL_CD) == 0;
+        }
 
-			int ret = controlOut(0x9a, 0x2518, lcr);
-			if (ret < 0) {
-				throw new IOException("Error setting control byte");
-			}
-		}
+        @Override
+        public boolean getCTS() throws IOException {
+            return (getStatus() & GCL_CTS) == 0;
+        }
 
-		@Override
-		public boolean getCD() throws IOException {
-			return (getStatus() & GCL_CD) == 0;
-		}
+        @Override
+        public boolean getDSR() throws IOException {
+            return (getStatus() & GCL_DSR) == 0;
+        }
 
-		@Override
-		public boolean getCTS() throws IOException {
-			return (getStatus() & GCL_CTS) == 0;
-		}
+        @Override
+        public boolean getDTR() throws IOException {
+            return dtr;
+        }
 
-		@Override
-		public boolean getDSR() throws IOException {
-			return (getStatus() & GCL_DSR) == 0;
-		}
+        @Override
+        public void setDTR(boolean value) throws IOException {
+            dtr = value;
+            setControlLines();
+        }
 
-		@Override
-		public boolean getDTR() throws IOException {
-			return dtr;
-		}
+        @Override
+        public boolean getRI() throws IOException {
+            return (getStatus() & GCL_RI) == 0;
+        }
 
-		@Override
-		public void setDTR(boolean value) throws IOException {
-			dtr = value;
-			setControlLines();
-		}
+        @Override
+        public boolean getRTS() throws IOException {
+            return rts;
+        }
 
-		@Override
-		public boolean getRI() throws IOException {
-			return (getStatus() & GCL_RI) == 0;
-		}
+        @Override
+        public void setRTS(boolean value) throws IOException {
+            rts = value;
+            setControlLines();
+        }
 
-		@Override
-		public boolean getRTS() throws IOException {
-			return rts;
-		}
+        @Override
+        public EnumSet<ControlLine> getControlLines() throws IOException {
+            int status = getStatus();
+            EnumSet<ControlLine> set = EnumSet.noneOf(ControlLine.class);
+            if(rts) set.add(ControlLine.RTS);
+            if((status & GCL_CTS) == 0) set.add(ControlLine.CTS);
+            if(dtr) set.add(ControlLine.DTR);
+            if((status & GCL_DSR) == 0) set.add(ControlLine.DSR);
+            if((status & GCL_CD) == 0) set.add(ControlLine.CD);
+            if((status & GCL_RI) == 0) set.add(ControlLine.RI);
+            return set;
+        }
 
-		@Override
-		public void setRTS(boolean value) throws IOException {
-			rts = value;
-			setControlLines();
-		}
+        @Override
+        public EnumSet<ControlLine> getSupportedControlLines() throws IOException {
+            return EnumSet.allOf(ControlLine.class);
+        }
 
-		@Override
-		public EnumSet<ControlLine> getControlLines() throws IOException {
-			int status = getStatus();
-			EnumSet<ControlLine> set = EnumSet.noneOf(ControlLine.class);
-			if(rts) set.add(ControlLine.RTS);
-			if((status & GCL_CTS) == 0) set.add(ControlLine.CTS);
-			if(dtr) set.add(ControlLine.DTR);
-			if((status & GCL_DSR) == 0) set.add(ControlLine.DSR);
-			if((status & GCL_CD) == 0) set.add(ControlLine.CD);
-			if((status & GCL_RI) == 0) set.add(ControlLine.RI);
-			return set;
-		}
+        @Override
+        public void setBreak(boolean value) throws IOException {
+            byte[] req = new byte[2];
+            if(controlIn(0x95, 0x1805, 0, req) < 0) {
+                throw new IOException("Error getting BREAK condition");
+            }
+            if(value) {
+                req[0] &= ~1;
+                req[1] &= ~0x40;
+            } else {
+                req[0] |= 1;
+                req[1] |= 0x40;
+            }
+            int val = (req[1] & 0xff) << 8 | (req[0] & 0xff);
+            if(controlOut(0x9a, 0x1805, val) < 0) {
+                throw new IOException("Error setting BREAK condition");
+            }
+        }
+    }
 
-		@Override
-		public EnumSet<ControlLine> getSupportedControlLines() throws IOException {
-			return EnumSet.allOf(ControlLine.class);
-		}
-	}
-
-	public static Map<Integer, int[]> getSupportedDevices() {
-		final Map<Integer, int[]> supportedDevices = new LinkedHashMap<Integer, int[]>();
-		supportedDevices.put(UsbId.VENDOR_QINHENG, new int[]{
-				UsbId.QINHENG_CH340,
-				UsbId.QINHENG_CH341A,
-		});
-		return supportedDevices;
-	}
+    @SuppressWarnings({"unused"})
+    public static Map<Integer, int[]> getSupportedDevices() {
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
+        supportedDevices.put(UsbId.VENDOR_QINHENG, new int[]{
+                UsbId.QINHENG_CH340,
+                UsbId.QINHENG_CH341A,
+        });
+        return supportedDevices;
+    }
 
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ChromeCcdSerialDriver.java

@@ -0,0 +1,91 @@
+package com.hoho.android.usbserial.driver;
+
+import android.hardware.usb.UsbConstants;
+import android.hardware.usb.UsbDevice;
+import android.hardware.usb.UsbEndpoint;
+import android.hardware.usb.UsbInterface;
+import android.util.Log;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+
+public class ChromeCcdSerialDriver implements UsbSerialDriver{
+
+    private final String TAG = ChromeCcdSerialDriver.class.getSimpleName();
+
+    private final UsbDevice mDevice;
+    private final List<UsbSerialPort> mPorts;
+
+    @Override
+    public UsbDevice getDevice() {
+        return mDevice;
+    }
+
+    @Override
+    public List<UsbSerialPort> getPorts() {
+        return mPorts;
+    }
+
+    public ChromeCcdSerialDriver(UsbDevice mDevice) {
+        this.mDevice = mDevice;
+        mPorts = new ArrayList<UsbSerialPort>();
+        for (int i = 0; i < 3; i++)
+            mPorts.add(new ChromeCcdSerialPort(mDevice, i));
+    }
+
+    public class ChromeCcdSerialPort extends CommonUsbSerialPort {
+        private UsbInterface mDataInterface;
+
+        public ChromeCcdSerialPort(UsbDevice device, int portNumber) {
+            super(device, portNumber);
+        }
+
+        @Override
+        protected void openInt() throws IOException {
+            Log.d(TAG, "claiming interfaces, count=" + mDevice.getInterfaceCount());
+            mDataInterface = mDevice.getInterface(mPortNumber);
+            if (!mConnection.claimInterface(mDataInterface, true)) {
+                throw new IOException("Could not claim shared control/data interface");
+            }
+            Log.d(TAG, "endpoint count=" + mDataInterface.getEndpointCount());
+            for (int i = 0; i < mDataInterface.getEndpointCount(); ++i) {
+                UsbEndpoint ep = mDataInterface.getEndpoint(i);
+                if ((ep.getDirection() == UsbConstants.USB_DIR_IN) && (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)) {
+                    mReadEndpoint = ep;
+                } else if ((ep.getDirection() == UsbConstants.USB_DIR_OUT) && (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)) {
+                    mWriteEndpoint = ep;
+                }
+            }
+        }
+
+        @Override
+        protected void closeInt() {
+            try {
+                mConnection.releaseInterface(mDataInterface);
+            } catch(Exception ignored) {}
+        }
+
+        @Override
+        public UsbSerialDriver getDriver() {
+            return ChromeCcdSerialDriver.this;
+        }
+
+        @Override
+        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+            throw new UnsupportedOperationException();
+        }
+    }
+
+    public static Map<Integer, int[]> getSupportedDevices() {
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
+        supportedDevices.put(UsbId.VENDOR_GOOGLE, new int[]{
+                UsbId.GOOGLE_CR50,
+        });
+        return supportedDevices;
+    }
+}

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java

@@ -10,8 +10,11 @@ import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbRequest;
+import android.os.Build;
 import android.util.Log;
 
+import com.hoho.android.usbserial.util.MonotonicClock;
+
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.EnumSet;
@@ -23,28 +26,33 @@ import java.util.EnumSet;
  */
 public abstract class CommonUsbSerialPort implements UsbSerialPort {
 
+    public static boolean DEBUG = false;
+
     private static final String TAG = CommonUsbSerialPort.class.getSimpleName();
-    private static final int DEFAULT_WRITE_BUFFER_SIZE = 16 * 1024;
-    private static final int MAX_READ_SIZE = 16 * 1024; // = old bulkTransfer limit
+    private static final int MAX_READ_SIZE = 16 * 1024; // = old bulkTransfer limit prior to Android 9
 
     protected final UsbDevice mDevice;
     protected final int mPortNumber;
 
     // non-null when open()
-    protected UsbDeviceConnection mConnection = null;
+    protected UsbDeviceConnection mConnection;
     protected UsbEndpoint mReadEndpoint;
     protected UsbEndpoint mWriteEndpoint;
     protected UsbRequest mUsbRequest;
+    protected FlowControl mFlowControl = FlowControl.NONE;
 
-    protected final Object mWriteBufferLock = new Object();
-    /** Internal write buffer.  Guarded by {@link #mWriteBufferLock}. */
+    /**
+     * Internal write buffer.
+     *  Guarded by {@link #mWriteBufferLock}.
+     *  Default length = mReadEndpoint.getMaxPacketSize()
+     **/
     protected byte[] mWriteBuffer;
+    protected final Object mWriteBufferLock = new Object();
+
 
     public CommonUsbSerialPort(UsbDevice device, int portNumber) {
         mDevice = device;
         mPortNumber = portNumber;
-
-        mWriteBuffer = new byte[DEFAULT_WRITE_BUFFER_SIZE];
     }
 
     @Override
@@ -63,7 +71,13 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     public int getPortNumber() {
         return mPortNumber;
     }
-    
+
+    @Override
+    public UsbEndpoint getWriteEndpoint() { return mWriteEndpoint; }
+
+    @Override
+    public UsbEndpoint getReadEndpoint() { return mReadEndpoint; }
+
     /**
      * Returns the device serial number
      *  @return serial number
@@ -77,11 +91,19 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
      * Sets the size of the internal buffer used to exchange data with the USB
      * stack for write operations.  Most users should not need to change this.
      *
-     * @param bufferSize the size in bytes
+     * @param bufferSize the size in bytes, <= 0 resets original size
      */
     public final void setWriteBufferSize(int bufferSize) {
         synchronized (mWriteBufferLock) {
-            if (bufferSize == mWriteBuffer.length) {
+            if (bufferSize <= 0) {
+                if (mWriteEndpoint != null) {
+                    bufferSize = mWriteEndpoint.getMaxPacketSize();
+                } else {
+                    mWriteBuffer = null;
+                    return;
+                }
+            }
+            if (mWriteBuffer != null && bufferSize == mWriteBuffer.length) {
                 return;
             }
             mWriteBuffer = new byte[bufferSize];
@@ -93,31 +115,40 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
         if (mConnection != null) {
             throw new IOException("Already open");
         }
+        if(connection == null) {
+            throw new IllegalArgumentException("Connection is null");
+        }
         mConnection = connection;
+        boolean ok = false;
         try {
-            openInt(connection);
+            openInt();
             if (mReadEndpoint == null || mWriteEndpoint == null) {
                 throw new IOException("Could not get read & write endpoints");
             }
             mUsbRequest = new UsbRequest();
             mUsbRequest.initialize(mConnection, mReadEndpoint);
-        } catch(Exception e) {
-            close();
-            throw e;
+            ok = true;
+        } finally {
+            if (!ok) {
+                try {
+                    close();
+                } catch (Exception ignored) {}
+            }
         }
     }
 
-    protected abstract void openInt(UsbDeviceConnection connection) throws IOException;
+    protected abstract void openInt() throws IOException;
 
     @Override
     public void close() throws IOException {
         if (mConnection == null) {
             throw new IOException("Already closed");
         }
-        try {
-            mUsbRequest.cancel();
-        } catch(Exception ignored) {}
+        UsbRequest usbRequest = mUsbRequest;
         mUsbRequest = null;
+        try {
+            usbRequest.cancel();
+        } catch(Exception ignored) {}
         try {
             closeInt();
         } catch(Exception ignored) {}
@@ -129,11 +160,43 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
 
     protected abstract void closeInt();
 
-    @Override
-    public int read(final byte[] dest, final int timeout) throws IOException {
-        if(mConnection == null) {
+    /**
+     * use simple USB request supported by all devices to test if connection is still valid
+     */
+    protected void testConnection(boolean full) throws IOException {
+        testConnection(full, "USB get_status request failed");
+    }
+
+    protected void testConnection(boolean full, String msg) throws IOException {
+        if(mUsbRequest == null) {
             throw new IOException("Connection closed");
         }
+        if(!full) {
+            return;
+        }
+        byte[] buf = new byte[2];
+        int len = mConnection.controlTransfer(0x80 /*DEVICE*/, 0 /*GET_STATUS*/, 0, 0, buf, buf.length, 200);
+        if(len < 0)
+            throw new IOException(msg);
+    }
+
+    @Override
+    public int read(final byte[] dest, final int timeout) throws IOException {
+        if(dest.length == 0) {
+            throw new IllegalArgumentException("Read buffer too small");
+        }
+        return read(dest, dest.length, timeout);
+    }
+
+    @Override
+    public int read(final byte[] dest, final int length, final int timeout) throws IOException {return read(dest, length, timeout, true);}
+
+    protected int read(final byte[] dest, int length, final int timeout, boolean testConnection) throws IOException {
+        testConnection(false);
+        if(length <= 0) {
+            throw new IllegalArgumentException("Read length too small");
+        }
+        length = Math.min(length, dest.length);
         final int nread;
         if (timeout != 0) {
             // bulkTransfer will cause data loss with short timeout + high baud rates + continuous transfer
@@ -144,12 +207,17 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
             //     /system/lib64/libusbhost.so (usb_request_wait+192)
             //     /system/lib64/libandroid_runtime.so (android_hardware_UsbDeviceConnection_request_wait(_JNIEnv*, _jobject*, long)+84)
             // data loss / crashes were observed with timeout up to 200 msec
-            int readMax = Math.min(dest.length, MAX_READ_SIZE);
+            long endTime = testConnection ? MonotonicClock.millis() + timeout : 0;
+            int readMax = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) ? length : Math.min(length, MAX_READ_SIZE);
             nread = mConnection.bulkTransfer(mReadEndpoint, dest, readMax, timeout);
+            // Android error propagation is improvable:
+            //  nread == -1 can be: timeout, connection lost, buffer to small, ???
+            if(nread == -1 && testConnection)
+                testConnection(MonotonicClock.millis() < endTime);
 
         } else {
-            final ByteBuffer buf = ByteBuffer.wrap(dest);
-            if (!mUsbRequest.queue(buf, dest.length)) {
+            final ByteBuffer buf = ByteBuffer.wrap(dest, 0, length);
+            if (!mUsbRequest.queue(buf, length)) {
                 throw new IOException("Queueing USB request failed");
             }
             final UsbRequest response = mConnection.requestWait();
@@ -157,59 +225,83 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
                 throw new IOException("Waiting for USB request failed");
             }
             nread = buf.position();
+            // Android error propagation is improvable:
+            //   response != null & nread == 0 can be: connection lost, buffer to small, ???
+            if(nread == 0) {
+                testConnection(true);
+            }
         }
-        if (nread > 0) {
-            return readFilter(dest, nread);
-        } else {
-            return 0;
-        }
+        return Math.max(nread, 0);
     }
 
-    protected int readFilter(final byte[] buffer, int len) throws IOException { return len; }
+    @Override
+    public void write(byte[] src, int timeout) throws IOException {write(src, src.length, timeout);}
 
     @Override
-    public int write(final byte[] src, final int timeout) throws IOException {
+    public void write(final byte[] src, int length, final int timeout) throws IOException {
         int offset = 0;
+        long startTime = MonotonicClock.millis();
+        length = Math.min(length, src.length);
 
-        if(mConnection == null) {
-            throw new IOException("Connection closed");
-        }
-        while (offset < src.length) {
-            final int writeLength;
-            final int amtWritten;
+        testConnection(false);
+        while (offset < length) {
+            int requestTimeout;
+            final int requestLength;
+            final int actualLength;
 
             synchronized (mWriteBufferLock) {
                 final byte[] writeBuffer;
 
-                writeLength = Math.min(src.length - offset, mWriteBuffer.length);
+                if (mWriteBuffer == null) {
+                    mWriteBuffer = new byte[mWriteEndpoint.getMaxPacketSize()];
+                }
+                requestLength = Math.min(length - offset, mWriteBuffer.length);
                 if (offset == 0) {
                     writeBuffer = src;
                 } else {
                     // bulkTransfer does not support offsets, make a copy.
-                    System.arraycopy(src, offset, mWriteBuffer, 0, writeLength);
+                    System.arraycopy(src, offset, mWriteBuffer, 0, requestLength);
                     writeBuffer = mWriteBuffer;
                 }
-
-                amtWritten = mConnection.bulkTransfer(mWriteEndpoint, writeBuffer, writeLength, timeout);
+                if (timeout == 0 || offset == 0) {
+                    requestTimeout = timeout;
+                } else {
+                    requestTimeout = (int)(startTime + timeout - MonotonicClock.millis());
+                    if(requestTimeout == 0)
+                        requestTimeout = -1;
+                }
+                if (requestTimeout < 0) {
+                    actualLength = -2;
+                } else {
+                    actualLength = mConnection.bulkTransfer(mWriteEndpoint, writeBuffer, requestLength, requestTimeout);
+                }
             }
-            if (amtWritten <= 0) {
-                throw new IOException("Error writing " + writeLength
-                        + " bytes at offset " + offset + " length=" + src.length);
+            long elapsed = MonotonicClock.millis() - startTime;
+            if (DEBUG) {
+                Log.d(TAG, "Wrote " + actualLength + "/" + requestLength + " offset " + offset + "/" + length + " time " + elapsed + "/" + requestTimeout);
             }
+            if (actualLength <= 0) {
+                String msg = "Error writing " + requestLength + " bytes at offset " + offset + " of total " + src.length + " after " + elapsed + "msec, rc=" + actualLength;
+                if (timeout != 0) {
+                    // could be buffer full because: writing to fast, stopped by flow control
+                    testConnection(elapsed < timeout, msg);
+                    throw new SerialTimeoutException(msg, offset);
+                } else {
+                    throw new IOException(msg);
 
-            Log.d(TAG, "Wrote amt=" + amtWritten + " attempted=" + writeLength);
-            offset += amtWritten;
+                }
+            }
+            offset += actualLength;
         }
-        return offset;
     }
 
     @Override
     public boolean isOpen() {
-        return mConnection != null;
+        return mUsbRequest != null;
     }
 
     @Override
-    public abstract void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException;
+    public abstract void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException;
 
     @Override
     public boolean getCD() throws IOException { throw new UnsupportedOperationException(); }
@@ -236,14 +328,30 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     public void setRTS(boolean value) throws IOException { throw new UnsupportedOperationException(); }
 
     @Override
-    public abstract EnumSet<ControlLine> getControlLines() throws IOException;
+    public EnumSet<ControlLine> getControlLines() throws IOException { throw new UnsupportedOperationException(); }
 
     @Override
-    public abstract EnumSet<ControlLine> getSupportedControlLines() throws IOException;
+    public EnumSet<ControlLine> getSupportedControlLines() throws IOException { return EnumSet.noneOf(ControlLine.class); }
 
     @Override
-    public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException {
-        throw new UnsupportedOperationException();
+    public void setFlowControl(FlowControl flowcontrol) throws IOException {
+        if (flowcontrol != FlowControl.NONE)
+            throw new UnsupportedOperationException();
     }
 
+    @Override
+    public FlowControl getFlowControl() { return mFlowControl; }
+
+    @Override
+    public EnumSet<FlowControl> getSupportedFlowControl() { return EnumSet.of(FlowControl.NONE); }
+
+    @Override
+    public boolean getXON() throws IOException { throw new UnsupportedOperationException(); }
+
+    @Override
+    public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException { throw new UnsupportedOperationException(); }
+
+    @Override
+    public void setBreak(boolean value) throws IOException { throw new UnsupportedOperationException(); }
+
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/Cp21xxSerialDriver.java

@@ -8,7 +8,6 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDevice;
-import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbInterface;
 
@@ -59,10 +58,16 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
          */
         private static final int SILABSER_IFC_ENABLE_REQUEST_CODE = 0x00;
         private static final int SILABSER_SET_LINE_CTL_REQUEST_CODE = 0x03;
+        private static final int SILABSER_SET_BREAK_REQUEST_CODE = 0x05;
         private static final int SILABSER_SET_MHS_REQUEST_CODE = 0x07;
-        private static final int SILABSER_SET_BAUDRATE = 0x1E;
-        private static final int SILABSER_FLUSH_REQUEST_CODE = 0x12;
         private static final int SILABSER_GET_MDMSTS_REQUEST_CODE = 0x08;
+        private static final int SILABSER_SET_XON_REQUEST_CODE = 0x09;
+        private static final int SILABSER_SET_XOFF_REQUEST_CODE = 0x0A;
+        private static final int SILABSER_GET_COMM_STATUS_REQUEST_CODE = 0x10;
+        private static final int SILABSER_FLUSH_REQUEST_CODE = 0x12;
+        private static final int SILABSER_SET_FLOW_REQUEST_CODE = 0x13;
+        private static final int SILABSER_SET_CHARS_REQUEST_CODE = 0x19;
+        private static final int SILABSER_SET_BAUDRATE_REQUEST_CODE = 0x1E;
 
         private static final int FLUSH_READ_CODE = 0x0a;
         private static final int FLUSH_WRITE_CODE = 0x05;
@@ -84,6 +89,8 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
         /*
         * SILABSER_GET_MDMSTS_REQUEST_CODE
          */
+        private static final int STATUS_DTR = 0x01;
+        private static final int STATUS_RTS = 0x02;
         private static final int STATUS_CTS = 0x10;
         private static final int STATUS_DSR = 0x20;
         private static final int STATUS_RI = 0x40;
@@ -118,14 +125,14 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
             byte[] buffer = new byte[1];
             int result = mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, SILABSER_GET_MDMSTS_REQUEST_CODE, 0,
                     mPortNumber, buffer, buffer.length, USB_WRITE_TIMEOUT_MILLIS);
-            if (result != 1) {
+            if (result != buffer.length) {
                 throw new IOException("Control transfer failed: " + SILABSER_GET_MDMSTS_REQUEST_CODE + " / " + 0 + " -> " + result);
             }
             return buffer[0];
         }
 
         @Override
-        protected void openInt(UsbDeviceConnection connection) throws IOException {
+        protected void openInt() throws IOException {
             mIsRestrictedPort = mDevice.getInterfaceCount() == 2 && mPortNumber == 1;
             if(mPortNumber >= mDevice.getInterfaceCount()) {
                 throw new IOException("Unknown port number");
@@ -147,6 +154,7 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
 
             setConfigSingle(SILABSER_IFC_ENABLE_REQUEST_CODE, UART_ENABLE);
             setConfigSingle(SILABSER_SET_MHS_REQUEST_CODE, (dtr ? DTR_ENABLE : DTR_DISABLE) | (rts ? RTS_ENABLE : RTS_DISABLE));
+            setFlowControl(mFlowControl);
         }
 
         @Override
@@ -166,7 +174,7 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
                     (byte) ((baudRate >> 16) & 0xff),
                     (byte) ((baudRate >> 24) & 0xff)
             };
-            int ret = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SILABSER_SET_BAUDRATE,
+            int ret = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SILABSER_SET_BAUDRATE_REQUEST_CODE,
                     0, mPortNumber, data, 4, USB_WRITE_TIMEOUT_MILLIS);
             if (ret < 0) {
                 throw new IOException("Error setting baud rate");
@@ -174,7 +182,7 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+        public void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException {
             if(baudRate <= 0) {
                 throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
             }
@@ -289,9 +297,11 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
         public EnumSet<ControlLine> getControlLines() throws IOException {
             byte status = getStatus();
             EnumSet<ControlLine> set = EnumSet.noneOf(ControlLine.class);
-            if(rts) set.add(ControlLine.RTS);
+            //if(rts) set.add(ControlLine.RTS);                      // configured value
+            if((status & STATUS_RTS) != 0) set.add(ControlLine.RTS); // actual value
             if((status & STATUS_CTS) != 0) set.add(ControlLine.CTS);
-            if(dtr) set.add(ControlLine.DTR);
+            //if(dtr) set.add(ControlLine.DTR);                      // configured value
+            if((status & STATUS_DTR) != 0) set.add(ControlLine.DTR); // actual value
             if((status & STATUS_DSR) != 0) set.add(ControlLine.DSR);
             if((status & STATUS_CD) != 0) set.add(ControlLine.CD);
             if((status & STATUS_RI) != 0) set.add(ControlLine.RI);
@@ -303,6 +313,73 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
             return EnumSet.allOf(ControlLine.class);
         }
 
+        @Override
+        public boolean getXON() throws IOException {
+            byte[] buffer = new byte[0x13];
+            int result = mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, SILABSER_GET_COMM_STATUS_REQUEST_CODE, 0,
+                    mPortNumber, buffer, buffer.length, USB_WRITE_TIMEOUT_MILLIS);
+            if (result != buffer.length) {
+                throw new IOException("Control transfer failed: " + SILABSER_GET_COMM_STATUS_REQUEST_CODE + " -> " + result);
+            }
+            return (buffer[4] & 8) == 0;
+        }
+
+        /**
+         * emulate external XON/OFF
+         * @throws IOException
+         */
+        public void setXON(boolean value) throws IOException {
+            setConfigSingle(value ? SILABSER_SET_XON_REQUEST_CODE : SILABSER_SET_XOFF_REQUEST_CODE, 0);
+        }
+
+        @Override
+        public void setFlowControl(FlowControl flowControl) throws IOException {
+            byte[] data = new byte[16];
+            if(flowControl == FlowControl.RTS_CTS) {
+                data[4] |=  0b1000_0000; // RTS
+                data[0] |=  0b0000_1000; // CTS
+            } else {
+                if(rts)
+                    data[4] |= 0b0100_0000;
+            }
+            if(flowControl == FlowControl.DTR_DSR) {
+                data[0] |= 0b0000_0010; // DTR
+                data[0] |= 0b0001_0000; // DSR
+            } else {
+                if(dtr)
+                    data[0] |= 0b0000_0001;
+            }
+            if(flowControl == FlowControl.XON_XOFF) {
+                byte[] chars = new byte[]{0, 0, 0, 0, CHAR_XON, CHAR_XOFF};
+                int ret = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SILABSER_SET_CHARS_REQUEST_CODE,
+                        0, mPortNumber, chars, chars.length, USB_WRITE_TIMEOUT_MILLIS);
+                if (ret != chars.length) {
+                    throw new IOException("Error setting XON/XOFF chars");
+                }
+                data[4] |= 0b0000_0011;
+                data[7] |= 0b1000_0000;
+                data[8] = (byte)128;
+                data[12] = (byte)128;
+            }
+            if(flowControl == FlowControl.XON_XOFF_INLINE) {
+                throw new UnsupportedOperationException();
+            }
+            int ret = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SILABSER_SET_FLOW_REQUEST_CODE,
+                    0, mPortNumber, data, data.length, USB_WRITE_TIMEOUT_MILLIS);
+            if (ret != data.length) {
+                throw new IOException("Error setting flow control");
+            }
+            if(flowControl == FlowControl.XON_XOFF) {
+                setXON(true);
+            }
+            mFlowControl = flowControl;
+        }
+
+        @Override
+        public EnumSet<FlowControl> getSupportedFlowControl() {
+            return EnumSet.of(FlowControl.NONE, FlowControl.RTS_CTS, FlowControl.DTR_DSR, FlowControl.XON_XOFF);
+        }
+
         @Override
         // note: only working on some devices, on other devices ignored w/o error
         public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException {
@@ -314,16 +391,20 @@ public class Cp21xxSerialDriver implements UsbSerialDriver {
             }
         }
 
+        @Override
+        public void setBreak(boolean value) throws IOException {
+            setConfigSingle(SILABSER_SET_BREAK_REQUEST_CODE, value ? 1 : 0);
+        }
     }
 
+    @SuppressWarnings({"unused"})
     public static Map<Integer, int[]> getSupportedDevices() {
-        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<Integer, int[]>();
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
         supportedDevices.put(UsbId.VENDOR_SILABS,
                 new int[] {
-            UsbId.SILABS_CP2102,
+            UsbId.SILABS_CP2102, // same ID for CP2101, CP2103, CP2104, CP2109
             UsbId.SILABS_CP2105,
             UsbId.SILABS_CP2108,
-            UsbId.SILABS_CP2110
         });
         return supportedDevices;
     }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java

@@ -9,9 +9,10 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDevice;
-import android.hardware.usb.UsbDeviceConnection;
 import android.util.Log;
 
+import com.hoho.android.usbserial.util.MonotonicClock;
+
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.EnumSet;
@@ -63,6 +64,7 @@ public class FtdiSerialDriver implements UsbSerialDriver {
 
         private static final int RESET_REQUEST = 0;
         private static final int MODEM_CONTROL_REQUEST = 1;
+        private static final int SET_FLOW_CONTROL_REQUEST = 2;
         private static final int SET_BAUD_RATE_REQUEST = 3;
         private static final int SET_DATA_REQUEST = 4;
         private static final int GET_MODEM_STATUS_REQUEST = 5;
@@ -84,6 +86,7 @@ public class FtdiSerialDriver implements UsbSerialDriver {
         private boolean baudRateWithPort = false;
         private boolean dtr = false;
         private boolean rts = false;
+        private int breakConfig = 0;
 
         public FtdiSerialPort(UsbDevice device, int portNumber) {
             super(device, portNumber);
@@ -96,8 +99,8 @@ public class FtdiSerialDriver implements UsbSerialDriver {
 
 
         @Override
-        protected void openInt(UsbDeviceConnection connection) throws IOException {
-            if (!connection.claimInterface(mDevice.getInterface(mPortNumber), true)) {
+        protected void openInt() throws IOException {
+            if (!mConnection.claimInterface(mDevice.getInterface(mPortNumber), true)) {
                 throw new IOException("Could not claim interface " + mPortNumber);
             }
             if (mDevice.getInterface(mPortNumber).getEndpointCount() < 2) {
@@ -118,14 +121,16 @@ public class FtdiSerialDriver implements UsbSerialDriver {
             if (result != 0) {
                 throw new IOException("Init RTS,DTR failed: result=" + result);
             }
+            setFlowControl(mFlowControl);
 
             // mDevice.getVersion() would require API 23
-            byte[] rawDescriptors = connection.getRawDescriptors();
+            byte[] rawDescriptors = mConnection.getRawDescriptors();
             if(rawDescriptors == null || rawDescriptors.length < 14) {
                 throw new IOException("Could not get device descriptors");
             }
             int deviceType = rawDescriptors[13];
-            baudRateWithPort = deviceType == 7 || deviceType == 8 || deviceType == 9; // ...H devices
+            baudRateWithPort = deviceType == 7 || deviceType == 8 || deviceType == 9 // ...H devices
+                    || mDevice.getInterfaceCount() > 1; // FT2232C
         }
 
         @Override
@@ -136,6 +141,42 @@ public class FtdiSerialDriver implements UsbSerialDriver {
         }
 
         @Override
+        public int read(final byte[] dest, final int timeout) throws IOException
+        {
+            if(dest.length <= READ_HEADER_LENGTH) {
+                throw new IllegalArgumentException("Read buffer too small");
+                // could allocate larger buffer, including space for 2 header bytes, but this would
+                // result in buffers not being 64 byte aligned any more, causing data loss at continuous
+                // data transfer at high baud rates when buffers are fully filled.
+            }
+            return read(dest, dest.length, timeout);
+        }
+
+        @Override
+        public int read(final byte[] dest, int length, final int timeout) throws IOException {
+            if(length <= READ_HEADER_LENGTH) {
+                throw new IllegalArgumentException("Read length too small");
+                // could allocate larger buffer, including space for 2 header bytes, but this would
+                // result in buffers not being 64 byte aligned any more, causing data loss at continuous
+                // data transfer at high baud rates when buffers are fully filled.
+            }
+            length = Math.min(length, dest.length);
+            int nread;
+            if (timeout != 0) {
+                long endTime = MonotonicClock.millis() + timeout;
+                do {
+                    nread = super.read(dest, length, Math.max(1, (int)(endTime - MonotonicClock.millis())), false);
+                } while (nread == READ_HEADER_LENGTH && MonotonicClock.millis() < endTime);
+                if(nread <= 0)
+                    testConnection(MonotonicClock.millis() < endTime);
+            } else {
+                do {
+                    nread = super.read(dest, length, timeout);
+                } while (nread == READ_HEADER_LENGTH);
+            }
+            return readFilter(dest, nread);
+        }
+
         protected int readFilter(byte[] buffer, int totalBytesRead) throws IOException {
             final int maxPacketSize = mReadEndpoint.getMaxPacketSize();
             int destPos = 0;
@@ -146,13 +187,14 @@ public class FtdiSerialDriver implements UsbSerialDriver {
                 System.arraycopy(buffer, srcPos + READ_HEADER_LENGTH, buffer, destPos, length);
                 destPos += length;
             }
+            //Log.d(TAG, "read filter " + totalBytesRead + " -> " + destPos);
             return destPos;
         }
 
         private void setBaudrate(int baudRate) throws IOException {
             int divisor, subdivisor, effectiveBaudRate;
             if (baudRate > 3500000) {
-                throw new IOException("Baud rate to high");
+                throw new UnsupportedOperationException("Baud rate to high");
             } else if(baudRate >= 2500000) {
                 divisor = 0;
                 subdivisor = 0;
@@ -167,13 +209,13 @@ public class FtdiSerialDriver implements UsbSerialDriver {
                 subdivisor = divisor & 0x07;
                 divisor >>= 3;
                 if (divisor > 0x3fff) // exceeds bit 13 at 183 baud
-                    throw new IOException("Baud rate to low");
+                    throw new UnsupportedOperationException("Baud rate to low");
                 effectiveBaudRate = (24000000 << 1) / ((divisor << 3) + subdivisor);
                 effectiveBaudRate = (effectiveBaudRate +1) >> 1;
             }
             double baudRateError = Math.abs(1.0 - (effectiveBaudRate / (double)baudRate));
             if(baudRateError >= 0.031) // can happen only > 1.5Mbaud
-                throw new IOException(String.format("baud rate deviation %.1f%% is higher than allowed 3%%", baudRateError*100));
+                throw new UnsupportedOperationException(String.format("Baud rate deviation %.1f%% is higher than allowed 3%%", baudRateError*100));
             int value = divisor;
             int index = 0;
             switch(subdivisor) {
@@ -201,7 +243,7 @@ public class FtdiSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+        public void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException {
             if(baudRate <= 0) {
                 throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
             }
@@ -256,13 +298,14 @@ public class FtdiSerialDriver implements UsbSerialDriver {
             if (result != 0) {
                 throw new IOException("Setting parameters failed: result=" + result);
             }
+            breakConfig = config;
         }
 
         private int getStatus() throws IOException {
             byte[] data = new byte[2];
             int result = mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, GET_MODEM_STATUS_REQUEST,
                     0, mPortNumber+1, data, data.length, USB_WRITE_TIMEOUT_MILLIS);
-            if (result != 2) {
+            if (result != data.length) {
                 throw new IOException("Get modem status failed: result=" + result);
             }
             return data[0];
@@ -336,13 +379,45 @@ public class FtdiSerialDriver implements UsbSerialDriver {
             return EnumSet.allOf(ControlLine.class);
         }
 
+        @Override
+        public void setFlowControl(FlowControl flowControl) throws IOException {
+            int value = 0;
+            int index = mPortNumber+1;
+            switch (flowControl) {
+                case NONE:
+                    break;
+                case RTS_CTS:
+                    index |= 0x100;
+                    break;
+                case DTR_DSR:
+                    index |= 0x200;
+                    break;
+                case XON_XOFF_INLINE:
+                    value = CHAR_XON + (CHAR_XOFF << 8);
+                    index |= 0x400;
+                    break;
+                default:
+                    throw new UnsupportedOperationException();
+            }
+            int result = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SET_FLOW_CONTROL_REQUEST,
+                    value, index, null, 0, USB_WRITE_TIMEOUT_MILLIS);
+            if (result != 0)
+                throw new IOException("Set flow control failed: result=" + result);
+            mFlowControl = flowControl;
+        }
+
+        @Override
+        public EnumSet<FlowControl> getSupportedFlowControl() {
+            return EnumSet.of(FlowControl.NONE, FlowControl.RTS_CTS, FlowControl.DTR_DSR, FlowControl.XON_XOFF_INLINE);
+        }
+
         @Override
         public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException {
             if (purgeWriteBuffers) {
                 int result = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, RESET_REQUEST,
                         RESET_PURGE_RX, mPortNumber+1, null, 0, USB_WRITE_TIMEOUT_MILLIS);
                 if (result != 0) {
-                    throw new IOException("purge write buffer failed: result=" + result);
+                    throw new IOException("Purge write buffer failed: result=" + result);
                 }
             }
 
@@ -350,11 +425,22 @@ public class FtdiSerialDriver implements UsbSerialDriver {
                 int result = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, RESET_REQUEST,
                         RESET_PURGE_TX, mPortNumber+1, null, 0, USB_WRITE_TIMEOUT_MILLIS);
                 if (result != 0) {
-                    throw new IOException("purge read buffer failed: result=" + result);
+                    throw new IOException("Purge read buffer failed: result=" + result);
                 }
             }
         }
 
+        @Override
+        public void setBreak(boolean value) throws IOException {
+            int config = breakConfig;
+            if(value) config |= 0x4000;
+            int result = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SET_DATA_REQUEST,
+                    config, mPortNumber+1,null, 0, USB_WRITE_TIMEOUT_MILLIS);
+            if (result != 0) {
+                throw new IOException("Setting BREAK failed: result=" + result);
+            }
+        }
+
         public void setLatencyTimer(int latencyTime) throws IOException {
             int result = mConnection.controlTransfer(REQTYPE_HOST_TO_DEVICE, SET_LATENCY_TIMER_REQUEST,
                     latencyTime, mPortNumber+1, null, 0, USB_WRITE_TIMEOUT_MILLIS);
@@ -367,7 +453,7 @@ public class FtdiSerialDriver implements UsbSerialDriver {
             byte[] data = new byte[1];
             int result = mConnection.controlTransfer(REQTYPE_DEVICE_TO_HOST, GET_LATENCY_TIMER_REQUEST,
                     0, mPortNumber+1, data, data.length, USB_WRITE_TIMEOUT_MILLIS);
-            if (result != 1) {
+            if (result != data.length) {
                 throw new IOException("Get latency timer failed: result=" + result);
             }
             return data[0];
@@ -375,8 +461,9 @@ public class FtdiSerialDriver implements UsbSerialDriver {
 
     }
 
+    @SuppressWarnings({"unused"})
     public static Map<Integer, int[]> getSupportedDevices() {
-        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<Integer, int[]>();
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
         supportedDevices.put(UsbId.VENDOR_FTDI,
                 new int[] {
                     UsbId.FTDI_FT232R,

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/GsmModemSerialDriver.java

@@ -0,0 +1,102 @@
+package com.hoho.android.usbserial.driver;
+
+import android.hardware.usb.UsbConstants;
+import android.hardware.usb.UsbDevice;
+import android.hardware.usb.UsbEndpoint;
+import android.hardware.usb.UsbInterface;
+import android.util.Log;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public class GsmModemSerialDriver implements UsbSerialDriver{
+
+    private final String TAG = GsmModemSerialDriver.class.getSimpleName();
+
+    private final UsbDevice mDevice;
+    private final UsbSerialPort mPort;
+
+    @Override
+    public UsbDevice getDevice() {
+        return mDevice;
+    }
+
+    @Override
+    public List<UsbSerialPort> getPorts() {
+        return Collections.singletonList(mPort);
+    }
+
+    public GsmModemSerialDriver(UsbDevice mDevice) {
+        this.mDevice = mDevice;
+        mPort = new GsmModemSerialPort(mDevice, 0);
+    }
+
+    public class GsmModemSerialPort extends CommonUsbSerialPort {
+
+        private UsbInterface mDataInterface;
+
+        public GsmModemSerialPort(UsbDevice device, int portNumber) {
+            super(device, portNumber);
+        }
+
+        @Override
+        protected void openInt() throws IOException {
+            Log.d(TAG, "claiming interfaces, count=" + mDevice.getInterfaceCount());
+            mDataInterface = mDevice.getInterface(0);
+            if (!mConnection.claimInterface(mDataInterface, true)) {
+                throw new IOException("Could not claim shared control/data interface");
+            }
+            Log.d(TAG, "endpoint count=" + mDataInterface.getEndpointCount());
+            for (int i = 0; i < mDataInterface.getEndpointCount(); ++i) {
+                UsbEndpoint ep = mDataInterface.getEndpoint(i);
+                if ((ep.getDirection() == UsbConstants.USB_DIR_IN) && (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)) {
+                    mReadEndpoint = ep;
+                } else if ((ep.getDirection() == UsbConstants.USB_DIR_OUT) && (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)) {
+                    mWriteEndpoint = ep;
+                }
+            }
+            initGsmModem();
+        }
+
+        @Override
+        protected void closeInt() {
+            try {
+                mConnection.releaseInterface(mDataInterface);
+            } catch(Exception ignored) {}
+
+        }
+
+        private int initGsmModem() throws IOException {
+            int len = mConnection.controlTransfer(
+                    0x21, 0x22, 0x01, 0, null, 0, 5000);
+            if(len < 0) {
+                throw new IOException("init failed");
+            }
+            return len;
+        }
+
+        @Override
+        public UsbSerialDriver getDriver() {
+            return GsmModemSerialDriver.this;
+        }
+
+        @Override
+        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+            throw new UnsupportedOperationException();
+        }
+
+    }
+
+    public static Map<Integer, int[]> getSupportedDevices() {
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
+        supportedDevices.put(UsbId.VENDOR_UNISOC, new int[]{
+                UsbId.FIBOCOM_L610,
+                UsbId.FIBOCOM_L612,
+        });
+        return supportedDevices;
+    }
+}

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProbeTable.java

@@ -6,6 +6,7 @@
 
 package com.hoho.android.usbserial.driver;
 
+import android.hardware.usb.UsbDevice;
 import android.util.Pair;
 
 import java.lang.reflect.InvocationTargetException;
@@ -14,14 +15,14 @@ import java.util.LinkedHashMap;
 import java.util.Map;
 
 /**
- * Maps (vendor id, product id) pairs to the corresponding serial driver.
- *
- * @author mike wakerly (opensource@hoho.com)
+ * Maps (vendor id, product id) pairs to the corresponding serial driver,
+ * or invoke 'probe' method to check actual USB devices for matching interfaces.
  */
 public class ProbeTable {
 
-    private final Map<Pair<Integer, Integer>, Class<? extends UsbSerialDriver>> mProbeTable =
-            new LinkedHashMap<Pair<Integer,Integer>, Class<? extends UsbSerialDriver>>();
+    private final Map<Pair<Integer, Integer>, Class<? extends UsbSerialDriver>> mVidPidProbeTable =
+            new LinkedHashMap<>();
+    private final Map<Method, Class<? extends UsbSerialDriver>> mMethodProbeTable = new LinkedHashMap<>();
 
     /**
      * Adds or updates a (vendor, product) pair in the table.
@@ -33,7 +34,7 @@ public class ProbeTable {
      */
     public ProbeTable addProduct(int vendorId, int productId,
             Class<? extends UsbSerialDriver> driverClass) {
-        mProbeTable.put(Pair.create(vendorId, productId), driverClass);
+        mVidPidProbeTable.put(Pair.create(vendorId, productId), driverClass);
         return this;
     }
 
@@ -41,12 +42,11 @@ public class ProbeTable {
      * Internal method to add all supported products from
      * {@code getSupportedProducts} static method.
      *
-     * @param driverClass
-     * @return
+     * @param driverClass to be added
      */
     @SuppressWarnings("unchecked")
-    ProbeTable addDriver(Class<? extends UsbSerialDriver> driverClass) {
-        final Method method;
+    void addDriver(Class<? extends UsbSerialDriver> driverClass) {
+        Method method;
 
         try {
             method = driverClass.getMethod("getSupportedDevices");
@@ -68,20 +68,35 @@ public class ProbeTable {
             }
         }
 
-        return this;
+        try {
+            method = driverClass.getMethod("probe", UsbDevice.class);
+            mMethodProbeTable.put(method, driverClass);
+        } catch (SecurityException | NoSuchMethodException ignored) {
+        }
     }
 
     /**
-     * Returns the driver for the given (vendor, product) pair, or {@code null}
-     * if no match.
+     * Returns the driver for the given USB device, or {@code null} if no match.
      *
-     * @param vendorId the USB vendor id
-     * @param productId the USB product id
+     * @param usbDevice the USB device to be probed
      * @return the driver class matching this pair, or {@code null}
      */
-    public Class<? extends UsbSerialDriver> findDriver(int vendorId, int productId) {
-        final Pair<Integer, Integer> pair = Pair.create(vendorId, productId);
-        return mProbeTable.get(pair);
+    public Class<? extends UsbSerialDriver> findDriver(final UsbDevice usbDevice) {
+        final Pair<Integer, Integer> pair = Pair.create(usbDevice.getVendorId(), usbDevice.getProductId());
+        Class<? extends UsbSerialDriver> driverClass = mVidPidProbeTable.get(pair);
+        if (driverClass != null)
+            return driverClass;
+        for (Map.Entry<Method, Class<? extends UsbSerialDriver>> entry : mMethodProbeTable.entrySet()) {
+            try {
+                Method method = entry.getKey();
+                Object o = method.invoke(null, usbDevice);
+                if((boolean)o)
+                    return entry.getValue();
+            } catch (IllegalArgumentException | IllegalAccessException | InvocationTargetException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return null;
     }
 
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java

@@ -11,13 +11,14 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbConstants;
 import android.hardware.usb.UsbDevice;
-import android.hardware.usb.UsbDeviceConnection;
 import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbInterface;
 import android.util.Log;
 
+import com.hoho.android.usbserial.BuildConfig;
+import com.hoho.android.usbserial.util.MonotonicClock;
+
 import java.io.IOException;
-import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.LinkedHashMap;
@@ -28,6 +29,13 @@ public class ProlificSerialDriver implements UsbSerialDriver {
 
     private final String TAG = ProlificSerialDriver.class.getSimpleName();
 
+    private final static int[] standardBaudRates = {
+            75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, 19200,
+            28800, 38400, 57600, 115200, 128000, 134400, 161280, 201600, 230400, 268800,
+            403200, 460800, 614400, 806400, 921600, 1228800, 2457600, 3000000, 6000000
+    };
+    protected enum DeviceType { DEVICE_TYPE_01, DEVICE_TYPE_T, DEVICE_TYPE_HX, DEVICE_TYPE_HXN }
+
     private final UsbDevice mDevice;
     private final UsbSerialPort mPort;
 
@@ -53,31 +61,50 @@ public class ProlificSerialDriver implements UsbSerialDriver {
 
         private static final int USB_RECIP_INTERFACE = 0x01;
 
-        private static final int PROLIFIC_VENDOR_READ_REQUEST = 0x01;
-        private static final int PROLIFIC_VENDOR_WRITE_REQUEST = 0x01;
+        private static final int VENDOR_READ_REQUEST = 0x01;
+        private static final int VENDOR_WRITE_REQUEST = 0x01;
+        private static final int VENDOR_READ_HXN_REQUEST = 0x81;
+        private static final int VENDOR_WRITE_HXN_REQUEST = 0x80;
 
-        private static final int PROLIFIC_VENDOR_OUT_REQTYPE = UsbConstants.USB_DIR_OUT
-                | UsbConstants.USB_TYPE_VENDOR;
-
-        private static final int PROLIFIC_VENDOR_IN_REQTYPE = UsbConstants.USB_DIR_IN
-                | UsbConstants.USB_TYPE_VENDOR;
-
-        private static final int PROLIFIC_CTRL_OUT_REQTYPE = UsbConstants.USB_DIR_OUT
-                | UsbConstants.USB_TYPE_CLASS | USB_RECIP_INTERFACE;
+        private static final int VENDOR_OUT_REQTYPE = UsbConstants.USB_DIR_OUT | UsbConstants.USB_TYPE_VENDOR;
+        private static final int VENDOR_IN_REQTYPE = UsbConstants.USB_DIR_IN | UsbConstants.USB_TYPE_VENDOR;
+        private static final int CTRL_OUT_REQTYPE = UsbConstants.USB_DIR_OUT | UsbConstants.USB_TYPE_CLASS | USB_RECIP_INTERFACE;
 
         private static final int WRITE_ENDPOINT = 0x02;
         private static final int READ_ENDPOINT = 0x83;
         private static final int INTERRUPT_ENDPOINT = 0x81;
 
-        private static final int FLUSH_RX_REQUEST = 0x08; // RX @ Prolific device = write @ usb-serial-for-android library
+        private static final int RESET_HXN_REQUEST = 0x07;
+        private static final int FLUSH_RX_REQUEST = 0x08;
         private static final int FLUSH_TX_REQUEST = 0x09;
+        private static final int SET_LINE_REQUEST = 0x20; // same as CDC SET_LINE_CODING
+        private static final int SET_CONTROL_REQUEST = 0x22; // same as CDC SET_CONTROL_LINE_STATE
+        private static final int SEND_BREAK_REQUEST = 0x23; // same as CDC SEND_BREAK
+        private static final int GET_CONTROL_HXN_REQUEST = 0x80;
+        private static final int GET_CONTROL_REQUEST = 0x87;
+        private static final int STATUS_NOTIFICATION = 0xa1; // similar to CDC SERIAL_STATE but different length
 
-        private static final int SET_LINE_REQUEST = 0x20;
-        private static final int SET_CONTROL_REQUEST = 0x22;
+        /* RESET_HXN_REQUEST */
+        private static final int RESET_HXN_RX_PIPE = 1;
+        private static final int RESET_HXN_TX_PIPE = 2;
 
+        /* SET_CONTROL_REQUEST */
         private static final int CONTROL_DTR = 0x01;
         private static final int CONTROL_RTS = 0x02;
 
+        /* GET_CONTROL_REQUEST */
+        private static final int GET_CONTROL_FLAG_CD = 0x02;
+        private static final int GET_CONTROL_FLAG_DSR = 0x04;
+        private static final int GET_CONTROL_FLAG_RI = 0x01;
+        private static final int GET_CONTROL_FLAG_CTS = 0x08;
+
+        /* GET_CONTROL_HXN_REQUEST */
+        private static final int GET_CONTROL_HXN_FLAG_CD = 0x40;
+        private static final int GET_CONTROL_HXN_FLAG_DSR = 0x20;
+        private static final int GET_CONTROL_HXN_FLAG_RI = 0x80;
+        private static final int GET_CONTROL_HXN_FLAG_CTS = 0x08;
+
+        /* interrupt endpoint read */
         private static final int STATUS_FLAG_CD = 0x01;
         private static final int STATUS_FLAG_DSR = 0x02;
         private static final int STATUS_FLAG_RI = 0x08;
@@ -86,23 +113,16 @@ public class ProlificSerialDriver implements UsbSerialDriver {
         private static final int STATUS_BUFFER_SIZE = 10;
         private static final int STATUS_BYTE_IDX = 8;
 
-        private static final int DEVICE_TYPE_HX = 0;
-        private static final int DEVICE_TYPE_0 = 1;
-        private static final int DEVICE_TYPE_1 = 2;
-
-        private int mDeviceType = DEVICE_TYPE_HX;
-
+        protected DeviceType mDeviceType = DeviceType.DEVICE_TYPE_HX;
         private UsbEndpoint mInterruptEndpoint;
-
         private int mControlLinesValue = 0;
-
         private int mBaudRate = -1, mDataBits = -1, mStopBits = -1, mParity = -1;
 
         private int mStatus = 0;
         private volatile Thread mReadStatusThread = null;
         private final Object mReadStatusThreadLock = new Object();
-        boolean mStopReadStatusThread = false;
-        private IOException mReadStatusException = null;
+        private boolean mStopReadStatusThread = false;
+        private Exception mReadStatusException = null;
 
 
         public ProlificSerialPort(UsbDevice device, int portNumber) {
@@ -114,54 +134,53 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             return ProlificSerialDriver.this;
         }
 
-        private final byte[] inControlTransfer(int requestType, int request,
-                int value, int index, int length) throws IOException {
+        private byte[] inControlTransfer(int requestType, int request, int value, int index, int length) throws IOException {
             byte[] buffer = new byte[length];
-            int result = mConnection.controlTransfer(requestType, request, value,
-                    index, buffer, length, USB_READ_TIMEOUT_MILLIS);
+            int result = mConnection.controlTransfer(requestType, request, value, index, buffer, length, USB_READ_TIMEOUT_MILLIS);
             if (result != length) {
-                throw new IOException(
-                        String.format("ControlTransfer with value 0x%x failed: %d",
-                                value, result));
+                throw new IOException(String.format("ControlTransfer %s 0x%x failed: %d",mDeviceType.name(), value, result));
             }
             return buffer;
         }
 
-        private final void outControlTransfer(int requestType, int request,
-                int value, int index, byte[] data) throws IOException {
+        private void outControlTransfer(int requestType, int request, int value, int index, byte[] data) throws IOException {
             int length = (data == null) ? 0 : data.length;
-            int result = mConnection.controlTransfer(requestType, request, value,
-                    index, data, length, USB_WRITE_TIMEOUT_MILLIS);
+            int result = mConnection.controlTransfer(requestType, request, value, index, data, length, USB_WRITE_TIMEOUT_MILLIS);
             if (result != length) {
-                throw new IOException(
-                        String.format("ControlTransfer with value 0x%x failed: %d",
-                                value, result));
+                throw new IOException( String.format("ControlTransfer %s 0x%x failed: %d", mDeviceType.name(), value, result));
             }
         }
 
-        private final byte[] vendorIn(int value, int index, int length)
-                throws IOException {
-            return inControlTransfer(PROLIFIC_VENDOR_IN_REQTYPE,
-                    PROLIFIC_VENDOR_READ_REQUEST, value, index, length);
+        private byte[] vendorIn(int value, int index, int length) throws IOException {
+            int request = (mDeviceType == DeviceType.DEVICE_TYPE_HXN) ? VENDOR_READ_HXN_REQUEST : VENDOR_READ_REQUEST;
+            return inControlTransfer(VENDOR_IN_REQTYPE, request, value, index, length);
         }
 
-        private final void vendorOut(int value, int index, byte[] data)
-                throws IOException {
-            outControlTransfer(PROLIFIC_VENDOR_OUT_REQTYPE,
-                    PROLIFIC_VENDOR_WRITE_REQUEST, value, index, data);
+        private void vendorOut(int value, int index, byte[] data) throws IOException {
+            int request = (mDeviceType == DeviceType.DEVICE_TYPE_HXN) ? VENDOR_WRITE_HXN_REQUEST : VENDOR_WRITE_REQUEST;
+            outControlTransfer(VENDOR_OUT_REQTYPE, request, value, index, data);
         }
 
         private void resetDevice() throws IOException {
             purgeHwBuffers(true, true);
         }
 
-        private final void ctrlOut(int request, int value, int index, byte[] data)
-                throws IOException {
-            outControlTransfer(PROLIFIC_CTRL_OUT_REQTYPE, request, value, index,
-                    data);
+        private void ctrlOut(int request, int value, int index, byte[] data) throws IOException {
+            outControlTransfer(CTRL_OUT_REQTYPE, request, value, index, data);
+        }
+
+        private boolean testHxStatus() {
+            try {
+                inControlTransfer(VENDOR_IN_REQTYPE, VENDOR_READ_REQUEST, 0x8080, 0, 1);
+                return true;
+            } catch(IOException ignored) {
+                return false;
+            }
         }
 
         private void doBlackMagic() throws IOException {
+            if (mDeviceType == DeviceType.DEVICE_TYPE_HXN)
+                return;
             vendorIn(0x8484, 0, 1);
             vendorOut(0x0404, 0, null);
             vendorIn(0x8484, 0, 1);
@@ -172,7 +191,7 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             vendorIn(0x8383, 0, 1);
             vendorOut(0, 1, null);
             vendorOut(1, 0, null);
-            vendorOut(2, (mDeviceType == DEVICE_TYPE_HX) ? 0x44 : 0x24, null);
+            vendorOut(2, (mDeviceType == DeviceType.DEVICE_TYPE_01) ? 0x24 : 0x44, null);
         }
 
         private void setControlLines(int newControlLinesValue) throws IOException {
@@ -180,76 +199,76 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             mControlLinesValue = newControlLinesValue;
         }
 
-        private final void readStatusThreadFunction() {
+        private void readStatusThreadFunction() {
             try {
+                byte[] buffer = new byte[STATUS_BUFFER_SIZE];
                 while (!mStopReadStatusThread) {
-                    byte[] buffer = new byte[STATUS_BUFFER_SIZE];
-                    int readBytesCount = mConnection.bulkTransfer(mInterruptEndpoint,
-                            buffer,
-                            STATUS_BUFFER_SIZE,
-                            500);
+                    long endTime = MonotonicClock.millis() + 500;
+                    int readBytesCount = mConnection.bulkTransfer(mInterruptEndpoint, buffer, STATUS_BUFFER_SIZE, 500);
+                    if(readBytesCount == -1)
+                        testConnection(MonotonicClock.millis() < endTime);
                     if (readBytesCount > 0) {
-                        if (readBytesCount == STATUS_BUFFER_SIZE) {
-                            mStatus = buffer[STATUS_BYTE_IDX] & 0xff;
+                        if (readBytesCount != STATUS_BUFFER_SIZE) {
+                            throw new IOException("Invalid status notification, expected " + STATUS_BUFFER_SIZE + " bytes, got " + readBytesCount);
+                        } else if(buffer[0] != (byte)STATUS_NOTIFICATION ) {
+                            throw new IOException("Invalid status notification, expected " + STATUS_NOTIFICATION + " request, got " + buffer[0]);
                         } else {
-                            throw new IOException(
-                                    String.format("Invalid CTS / DSR / CD / RI status buffer received, expected %d bytes, but received %d",
-                                            STATUS_BUFFER_SIZE,
-                                            readBytesCount));
+                            mStatus = buffer[STATUS_BYTE_IDX] & 0xff;
                         }
                     }
                 }
-            } catch (IOException e) {
-                mReadStatusException = e;
+            } catch (Exception e) {
+                if (isOpen())
+                    mReadStatusException = e;
             }
+            //Log.d(TAG, "end control line status thread " + mStopReadStatusThread + " " + (mReadStatusException == null ? "-" : mReadStatusException.getMessage()));
         }
 
-        private final int getStatus() throws IOException {
+        private int getStatus() throws IOException {
             if ((mReadStatusThread == null) && (mReadStatusException == null)) {
                 synchronized (mReadStatusThreadLock) {
                     if (mReadStatusThread == null) {
-                        byte[] buffer = new byte[STATUS_BUFFER_SIZE];
-                        int readBytes = mConnection.bulkTransfer(mInterruptEndpoint,
-                                buffer,
-                                STATUS_BUFFER_SIZE,
-                                100);
-                        if (readBytes != STATUS_BUFFER_SIZE) {
-                            Log.w(TAG, "Could not read initial CTS / DSR / CD / RI status");
+                        mStatus = 0;
+                        if(mDeviceType == DeviceType.DEVICE_TYPE_HXN) {
+                            byte[] data = vendorIn(GET_CONTROL_HXN_REQUEST, 0, 1);
+                            if ((data[0] & GET_CONTROL_HXN_FLAG_CTS) == 0) mStatus |= STATUS_FLAG_CTS;
+                            if ((data[0] & GET_CONTROL_HXN_FLAG_DSR) == 0) mStatus |= STATUS_FLAG_DSR;
+                            if ((data[0] & GET_CONTROL_HXN_FLAG_CD) == 0) mStatus |= STATUS_FLAG_CD;
+                            if ((data[0] & GET_CONTROL_HXN_FLAG_RI) == 0) mStatus |= STATUS_FLAG_RI;
                         } else {
-                            mStatus = buffer[STATUS_BYTE_IDX] & 0xff;
+                            byte[] data = vendorIn(GET_CONTROL_REQUEST, 0, 1);
+                            if ((data[0] & GET_CONTROL_FLAG_CTS) == 0) mStatus |= STATUS_FLAG_CTS;
+                            if ((data[0] & GET_CONTROL_FLAG_DSR) == 0) mStatus |= STATUS_FLAG_DSR;
+                            if ((data[0] & GET_CONTROL_FLAG_CD) == 0) mStatus |= STATUS_FLAG_CD;
+                            if ((data[0] & GET_CONTROL_FLAG_RI) == 0) mStatus |= STATUS_FLAG_RI;
                         }
-
-                        mReadStatusThread = new Thread(new Runnable() {
-                            @Override
-                            public void run() {
-                                readStatusThreadFunction();
-                            }
-                        });
+                        //Log.d(TAG, "start control line status thread " + mStatus);
+                        mReadStatusThread = new Thread(this::readStatusThreadFunction);
                         mReadStatusThread.setDaemon(true);
                         mReadStatusThread.start();
                     }
                 }
             }
 
-            /* throw and clear an exception which occured in the status read thread */
-            IOException readStatusException = mReadStatusException;
+            /* throw and clear an exception which occurred in the status read thread */
+            Exception readStatusException = mReadStatusException;
             if (mReadStatusException != null) {
                 mReadStatusException = null;
-                throw readStatusException;
+                throw new IOException(readStatusException);
             }
 
             return mStatus;
         }
 
-        private final boolean testStatusFlag(int flag) throws IOException {
+        private boolean testStatusFlag(int flag) throws IOException {
             return ((getStatus() & flag) == flag);
         }
 
         @Override
-        public void openInt(UsbDeviceConnection connection) throws IOException {
+        public void openInt() throws IOException {
             UsbInterface usbInterface = mDevice.getInterface(0);
 
-            if (!connection.claimInterface(usbInterface, true)) {
+            if (!mConnection.claimInterface(usbInterface, true)) {
                 throw new IOException("Error claiming Prolific interface 0");
             }
 
@@ -271,51 +290,48 @@ public class ProlificSerialDriver implements UsbSerialDriver {
                 }
             }
 
-            if (mDevice.getDeviceClass() == 0x02) {
-                mDeviceType = DEVICE_TYPE_0;
-            } else {
-                try {
-                    Method getRawDescriptorsMethod
-                        = mConnection.getClass().getMethod("getRawDescriptors");
-                    byte[] rawDescriptors
-                        = (byte[]) getRawDescriptorsMethod.invoke(mConnection);
-                    byte maxPacketSize0 = rawDescriptors[7];
-                    if (maxPacketSize0 == 64) {
-                        mDeviceType = DEVICE_TYPE_HX;
-                    } else if ((mDevice.getDeviceClass() == 0x00)
-                            || (mDevice.getDeviceClass() == 0xff)) {
-                        mDeviceType = DEVICE_TYPE_1;
-                    } else {
-                      Log.w(TAG, "Could not detect PL2303 subtype, "
-                          + "Assuming that it is a HX device");
-                      mDeviceType = DEVICE_TYPE_HX;
-                    }
-                } catch (NoSuchMethodException e) {
-                    Log.w(TAG, "Method UsbDeviceConnection.getRawDescriptors, "
-                            + "required for PL2303 subtype detection, not "
-                            + "available! Assuming that it is a HX device");
-                    mDeviceType = DEVICE_TYPE_HX;
-                } catch (Exception e) {
-                    Log.e(TAG, "An unexpected exception occured while trying "
-                            + "to detect PL2303 subtype", e);
-                }
+            byte[] rawDescriptors = mConnection.getRawDescriptors();
+            if(rawDescriptors == null || rawDescriptors.length < 14) {
+                throw new IOException("Could not get device descriptors");
             }
-            setControlLines(mControlLinesValue);
+            int usbVersion = (rawDescriptors[3] << 8) + rawDescriptors[2];
+            int deviceVersion = (rawDescriptors[13] << 8) + rawDescriptors[12];
+            byte maxPacketSize0 = rawDescriptors[7];
+            if (mDevice.getDeviceClass() == 0x02 || maxPacketSize0 != 64) {
+                mDeviceType = DeviceType.DEVICE_TYPE_01;
+            } else if(usbVersion == 0x200) {
+                if(deviceVersion == 0x300 && testHxStatus()) {
+                    mDeviceType = DeviceType.DEVICE_TYPE_T; // TA
+                } else if(deviceVersion == 0x500 && testHxStatus()) {
+                    mDeviceType = DeviceType.DEVICE_TYPE_T; // TB
+                } else {
+                    mDeviceType = DeviceType.DEVICE_TYPE_HXN;
+                }
+            } else {
+                mDeviceType = DeviceType.DEVICE_TYPE_HX;
+            }
+            Log.d(TAG, String.format("usbVersion=%x, deviceVersion=%x, deviceClass=%d, packetSize=%d => deviceType=%s",
+                    usbVersion, deviceVersion, mDevice.getDeviceClass(), maxPacketSize0, mDeviceType.name()));
             resetDevice();
             doBlackMagic();
+            setControlLines(mControlLinesValue);
+            setFlowControl(mFlowControl);
         }
 
         @Override
         public void closeInt() {
             try {
-                mStopReadStatusThread = true;
                 synchronized (mReadStatusThreadLock) {
                     if (mReadStatusThread != null) {
                         try {
+                            mStopReadStatusThread = true;
                             mReadStatusThread.join();
                         } catch (Exception e) {
                             Log.w(TAG, "An error occured while waiting for status read thread", e);
                         }
+                        mStopReadStatusThread = false;
+                        mReadStatusThread = null;
+                        mReadStatusException = null;
                     }
                 }
                 resetDevice();
@@ -325,8 +341,79 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             } catch(Exception ignored) {}
         }
 
+        private int filterBaudRate(int baudRate) {
+            if(BuildConfig.DEBUG && (baudRate & (3<<29)) == (1<<29)) {
+                return baudRate & ~(1<<29); // for testing purposes accept without further checks
+            }
+            if (baudRate <= 0) {
+                throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
+            }
+            if (mDeviceType == DeviceType.DEVICE_TYPE_HXN) {
+                return baudRate;
+            }
+            for(int br : standardBaudRates) {
+                if (br == baudRate) {
+                    return baudRate;
+                }
+            }
+            /*
+             * Formula taken from Linux + FreeBSD.
+             *
+             * For TA+TB devices
+             *   baudrate = baseline / (mantissa * 2^exponent)
+             * where
+             *   mantissa = buf[10:0]
+             *   exponent = buf[15:13 16]
+             *
+             * For other devices
+             *   baudrate = baseline / (mantissa * 4^exponent)
+             * where
+             *   mantissa = buf[8:0]
+             *   exponent = buf[11:9]
+             *
+             */
+            int baseline, mantissa, exponent, buf, effectiveBaudRate;
+            baseline = 12000000 * 32;
+            mantissa = baseline / baudRate;
+            if (mantissa == 0) { // > unrealistic 384 MBaud
+                throw new UnsupportedOperationException("Baud rate to high");
+            }
+            exponent = 0;
+            if (mDeviceType == DeviceType.DEVICE_TYPE_T) {
+                while (mantissa >= 2048) {
+                    if (exponent < 15) {
+                        mantissa >>= 1;    /* divide by 2 */
+                        exponent++;
+                    } else { // < 7 baud
+                        throw new UnsupportedOperationException("Baud rate to low");
+                    }
+                }
+                buf = mantissa + ((exponent & ~1) << 12) + ((exponent & 1) << 16) + (1 << 31);
+                effectiveBaudRate = (baseline / mantissa) >> exponent;
+            } else {
+                while (mantissa >= 512) {
+                    if (exponent < 7) {
+                        mantissa >>= 2;    /* divide by 4 */
+                        exponent++;
+                    } else { // < 45.8 baud
+                        throw new UnsupportedOperationException("Baud rate to low");
+                    }
+                }
+                buf = mantissa + (exponent << 9) + (1 << 31);
+                effectiveBaudRate = (baseline / mantissa) >> (exponent << 1);
+            }
+            double baudRateError = Math.abs(1.0 - (effectiveBaudRate / (double)baudRate));
+            if(baudRateError >= 0.031) // > unrealistic 11.6 Mbaud
+                throw new UnsupportedOperationException(String.format("Baud rate deviation %.1f%% is higher than allowed 3%%", baudRateError*100));
+
+            Log.d(TAG, String.format("baud rate=%d, effective=%d, error=%.1f%%, value=0x%08x, mantissa=%d, exponent=%d",
+                    baudRate, effectiveBaudRate, baudRateError*100, buf, mantissa, exponent));
+            return buf;
+        }
+
         @Override
-        public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException {
+        public void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException {
+            baudRate = filterBaudRate(baudRate);
             if ((mBaudRate == baudRate) && (mDataBits == dataBits)
                     && (mStopBits == stopBits) && (mParity == parity)) {
                 // Make sure no action is performed if there is nothing to change
@@ -334,10 +421,6 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             }
 
             byte[] lineRequestData = new byte[7];
-
-            if(baudRate <= 0) {
-                throw new IllegalArgumentException("Invalid baud rate: " + baudRate);
-            }
             lineRequestData[0] = (byte) (baudRate & 0xff);
             lineRequestData[1] = (byte) ((baudRate >> 8) & 0xff);
             lineRequestData[2] = (byte) ((baudRate >> 16) & 0xff);
@@ -444,7 +527,6 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             setControlLines(newControlLinesValue);
         }
 
-
         @Override
         public EnumSet<ControlLine> getControlLines() throws IOException {
             int status = getStatus();
@@ -464,21 +546,73 @@ public class ProlificSerialDriver implements UsbSerialDriver {
         }
 
         @Override
-        public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException {
-            if (purgeWriteBuffers) {
-                vendorOut(FLUSH_RX_REQUEST, 0, null);
+        public void setFlowControl(FlowControl flowControl) throws IOException {
+            // vendorOut values from https://www.mail-archive.com/linux-usb@vger.kernel.org/msg110968.html
+            switch (flowControl) {
+                case NONE:
+                    if (mDeviceType == DeviceType.DEVICE_TYPE_HXN)
+                        vendorOut(0x0a, 0xff, null);
+                    else
+                        vendorOut(0, 0, null);
+                    break;
+                case RTS_CTS:
+                    if (mDeviceType == DeviceType.DEVICE_TYPE_HXN)
+                        vendorOut(0x0a, 0xfa, null);
+                    else
+                        vendorOut(0, 0x61, null);
+                    break;
+                case XON_XOFF_INLINE:
+                    if (mDeviceType == DeviceType.DEVICE_TYPE_HXN)
+                        vendorOut(0x0a, 0xee, null);
+                    else
+                        vendorOut(0, 0xc1, null);
+                    break;
+                default:
+                    throw new UnsupportedOperationException();
             }
+            mFlowControl = flowControl;
+        }
 
-            if (purgeReadBuffers) {
-                vendorOut(FLUSH_TX_REQUEST, 0, null);
+        @Override
+        public EnumSet<FlowControl> getSupportedFlowControl() {
+            return EnumSet.of(FlowControl.NONE, FlowControl.RTS_CTS, FlowControl.XON_XOFF_INLINE);
+        }
+
+        @Override
+        public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException {
+            if (mDeviceType == DeviceType.DEVICE_TYPE_HXN) {
+                int index = 0;
+                if(purgeWriteBuffers) index |= RESET_HXN_RX_PIPE;
+                if(purgeReadBuffers) index |= RESET_HXN_TX_PIPE;
+                if(index != 0)
+                    vendorOut(RESET_HXN_REQUEST, index, null);
+            } else {
+                if (purgeWriteBuffers)
+                    vendorOut(FLUSH_RX_REQUEST, 0, null);
+                if (purgeReadBuffers)
+                    vendorOut(FLUSH_TX_REQUEST, 0, null);
             }
         }
+
+        @Override
+        public void setBreak(boolean value) throws IOException {
+            ctrlOut(SEND_BREAK_REQUEST, value ? 0xffff : 0, 0, null);
+        }
     }
 
+    @SuppressWarnings({"unused"})
     public static Map<Integer, int[]> getSupportedDevices() {
-        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<Integer, int[]>();
+        final Map<Integer, int[]> supportedDevices = new LinkedHashMap<>();
         supportedDevices.put(UsbId.VENDOR_PROLIFIC,
-                new int[] { UsbId.PROLIFIC_PL2303, });
+                new int[] {
+                        UsbId.PROLIFIC_PL2303,
+                        UsbId.PROLIFIC_PL2303GC,
+                        UsbId.PROLIFIC_PL2303GB,
+                        UsbId.PROLIFIC_PL2303GT,
+                        UsbId.PROLIFIC_PL2303GL,
+                        UsbId.PROLIFIC_PL2303GE,
+                        UsbId.PROLIFIC_PL2303GS,
+                });
         return supportedDevices;
     }
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/SerialTimeoutException.java

@@ -0,0 +1,16 @@
+package com.hoho.android.usbserial.driver;
+
+import java.io.InterruptedIOException;
+
+/**
+ * Signals that a timeout has occurred on serial write.
+ * Similar to SocketTimeoutException.
+ *
+ * {@see InterruptedIOException#bytesTransferred} may contain bytes transferred
+ */
+public class SerialTimeoutException extends InterruptedIOException {
+    public SerialTimeoutException(String s, int bytesTransferred) {
+        super(s);
+        this.bytesTransferred = bytesTransferred;
+    }
+}

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/UsbId.java

@@ -23,43 +23,31 @@ public final class UsbId {
     public static final int FTDI_FT232H = 0x6014;
     public static final int FTDI_FT231X = 0x6015; // same ID for FT230X, FT231X, FT234XD
 
-    public static final int VENDOR_ATMEL = 0x03EB;
-    public static final int ATMEL_LUFA_CDC_DEMO_APP = 0x2044;
-
-    public static final int VENDOR_ARDUINO = 0x2341;
-    public static final int ARDUINO_UNO = 0x0001;
-    public static final int ARDUINO_MEGA_2560 = 0x0010;
-    public static final int ARDUINO_SERIAL_ADAPTER = 0x003b;
-    public static final int ARDUINO_MEGA_ADK = 0x003f;
-    public static final int ARDUINO_MEGA_2560_R3 = 0x0042;
-    public static final int ARDUINO_UNO_R3 = 0x0043;
-    public static final int ARDUINO_MEGA_ADK_R3 = 0x0044;
-    public static final int ARDUINO_SERIAL_ADAPTER_R3 = 0x0044;
-    public static final int ARDUINO_LEONARDO = 0x8036;
-    public static final int ARDUINO_MICRO = 0x8037;
-
-    public static final int VENDOR_VAN_OOIJEN_TECH = 0x16c0;
-    public static final int VAN_OOIJEN_TECH_TEENSYDUINO_SERIAL = 0x0483;
-
-    public static final int VENDOR_LEAFLABS = 0x1eaf;
-    public static final int LEAFLABS_MAPLE = 0x0004;
-
     public static final int VENDOR_SILABS = 0x10c4;
-    public static final int SILABS_CP2102 = 0xea60;
+    public static final int SILABS_CP2102 = 0xea60; // same ID for CP2101, CP2103, CP2104, CP2109
     public static final int SILABS_CP2105 = 0xea70;
     public static final int SILABS_CP2108 = 0xea71;
-    public static final int SILABS_CP2110 = 0xea80;
 
     public static final int VENDOR_PROLIFIC = 0x067b;
-    public static final int PROLIFIC_PL2303 = 0x2303;
+    public static final int PROLIFIC_PL2303 = 0x2303;   // device type 01, T, HX
+    public static final int PROLIFIC_PL2303GC = 0x23a3; // device type HXN
+    public static final int PROLIFIC_PL2303GB = 0x23b3; // "
+    public static final int PROLIFIC_PL2303GT = 0x23c3; // "
+    public static final int PROLIFIC_PL2303GL = 0x23d3; // "
+    public static final int PROLIFIC_PL2303GE = 0x23e3; // "
+    public static final int PROLIFIC_PL2303GS = 0x23f3; // "
+
+    public static final int VENDOR_GOOGLE = 0x18d1;
+    public static final int GOOGLE_CR50 = 0x5014;
 
     public static final int VENDOR_QINHENG = 0x1a86;
     public static final int QINHENG_CH340 = 0x7523;
     public static final int QINHENG_CH341A = 0x5523;
 
-    // at www.linux-usb.org/usb.ids listed for NXP/LPC1768, but all processors supported by ARM mbed DAPLink firmware report these ids
-    public static final int VENDOR_ARM = 0x0d28;
-    public static final int ARM_MBED = 0x0204;
+    public static final int VENDOR_UNISOC = 0x1782;
+    public static final int FIBOCOM_L610 = 0x4D10;
+    public static final int FIBOCOM_L612 = 0x4D12;
+
 
     private UsbId() {
         throw new IllegalAccessError("Non-instantiable class");

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/UsbSerialDriver.java

@@ -10,18 +10,23 @@ import android.hardware.usb.UsbDevice;
 
 import java.util.List;
 
-/**
- *
- * @author mike wakerly (opensource@hoho.com)
- */
 public interface UsbSerialDriver {
 
+    /*
+     * Additional interface properties. Invoked thru reflection.
+     *
+        UsbSerialDriver(UsbDevice device);                  // constructor with device
+        static Map<Integer, int[]> getSupportedDevices();
+        static boolean probe(UsbDevice device);             // optional
+     */
+
+
     /**
      * Returns the raw {@link UsbDevice} backing this port.
      *
      * @return the device
      */
-    public UsbDevice getDevice();
+    UsbDevice getDevice();
 
     /**
      * Returns all available ports for this device. This list must have at least
@@ -29,5 +34,5 @@ public interface UsbSerialDriver {
      *
      * @return the ports
      */
-    public List<UsbSerialPort> getPorts();
+    List<UsbSerialPort> getPorts();
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/UsbSerialPort.java

@@ -8,10 +8,15 @@ package com.hoho.android.usbserial.driver;
 
 import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbDeviceConnection;
+import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbManager;
 
+import androidx.annotation.IntDef;
+
 import java.io.Closeable;
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.EnumSet;
 
 /**
@@ -22,81 +27,82 @@ import java.util.EnumSet;
 public interface UsbSerialPort extends Closeable {
 
     /** 5 data bits. */
-    public static final int DATABITS_5 = 5;
-
+    int DATABITS_5 = 5;
     /** 6 data bits. */
-    public static final int DATABITS_6 = 6;
-
+    int DATABITS_6 = 6;
     /** 7 data bits. */
-    public static final int DATABITS_7 = 7;
-
+    int DATABITS_7 = 7;
     /** 8 data bits. */
-    public static final int DATABITS_8 = 8;
-
-    /** No flow control. */
-    public static final int FLOWCONTROL_NONE = 0;
-
-    /** RTS/CTS input flow control. */
-    public static final int FLOWCONTROL_RTSCTS_IN = 1;
-
-    /** RTS/CTS output flow control. */
-    public static final int FLOWCONTROL_RTSCTS_OUT = 2;
-
-    /** XON/XOFF input flow control. */
-    public static final int FLOWCONTROL_XONXOFF_IN = 4;
-
-    /** XON/XOFF output flow control. */
-    public static final int FLOWCONTROL_XONXOFF_OUT = 8;
+    int DATABITS_8 = 8;
 
+    /** Values for setParameters(..., parity) */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef({PARITY_NONE, PARITY_ODD, PARITY_EVEN, PARITY_MARK, PARITY_SPACE})
+    @interface Parity {}
     /** No parity. */
-    public static final int PARITY_NONE = 0;
-
+    int PARITY_NONE = 0;
     /** Odd parity. */
-    public static final int PARITY_ODD = 1;
-
+    int PARITY_ODD = 1;
     /** Even parity. */
-    public static final int PARITY_EVEN = 2;
-
+    int PARITY_EVEN = 2;
     /** Mark parity. */
-    public static final int PARITY_MARK = 3;
-
+    int PARITY_MARK = 3;
     /** Space parity. */
-    public static final int PARITY_SPACE = 4;
+    int PARITY_SPACE = 4;
 
     /** 1 stop bit. */
-    public static final int STOPBITS_1 = 1;
-
+    int STOPBITS_1 = 1;
     /** 1.5 stop bits. */
-    public static final int STOPBITS_1_5 = 3;
-
+    int STOPBITS_1_5 = 3;
     /** 2 stop bits. */
-    public static final int STOPBITS_2 = 2;
+    int STOPBITS_2 = 2;
+
+    /** Values for get[Supported]ControlLines() */
+    enum ControlLine { RTS, CTS, DTR, DSR, CD, RI }
+
+    /** Values for (set|get|getSupported)FlowControl() */
+    enum FlowControl { NONE, RTS_CTS, DTR_DSR, XON_XOFF, XON_XOFF_INLINE }
+
+    /** XON character used with flow control XON/XOFF */
+    char CHAR_XON = 17;
+    /** XOFF character used with flow control XON/XOFF */
+    char CHAR_XOFF = 19;
 
-    /** values for get[Supported]ControlLines() */
-    public enum ControlLine { RTS, CTS,  DTR, DSR,  CD, RI };
 
     /**
      * Returns the driver used by this port.
      */
-    public UsbSerialDriver getDriver();
+    UsbSerialDriver getDriver();
 
     /**
      * Returns the currently-bound USB device.
      */
-    public UsbDevice getDevice();
+    UsbDevice getDevice();
 
     /**
      * Port number within driver.
      */
-    public int getPortNumber();
-    
+    int getPortNumber();
+
+    /**
+     * Returns the write endpoint.
+     * @return write endpoint
+     */
+    UsbEndpoint getWriteEndpoint();
+
+    /**
+     * Returns the read endpoint.
+     * @return read endpoint
+     */
+    UsbEndpoint getReadEndpoint();
+
     /**
      * The serial number of the underlying UsbDeviceConnection, or {@code null}.
      *
      * @return value from {@link UsbDeviceConnection#getSerial()}
      * @throws SecurityException starting with target SDK 29 (Android 10) if permission for USB device is not granted
      */
-    public String getSerial();
+    String getSerial();
 
     /**
      * Opens and initializes the port. Upon success, caller must ensure that
@@ -106,14 +112,14 @@ public interface UsbSerialPort extends Closeable {
      *                   {@link UsbManager#openDevice(android.hardware.usb.UsbDevice)}
      * @throws IOException on error opening or initializing the port.
      */
-    public void open(UsbDeviceConnection connection) throws IOException;
+    void open(UsbDeviceConnection connection) throws IOException;
 
     /**
      * Closes the port and {@link UsbDeviceConnection}
      *
      * @throws IOException on error closing the port.
      */
-    public void close() throws IOException;
+    void close() throws IOException;
 
     /**
      * Reads as many bytes as possible into the destination buffer.
@@ -123,17 +129,41 @@ public interface UsbSerialPort extends Closeable {
      * @return the actual number of bytes read
      * @throws IOException if an error occurred during reading
      */
-    public int read(final byte[] dest, final int timeout) throws IOException;
+    int read(final byte[] dest, final int timeout) throws IOException;
+
+    /**
+     * Reads bytes with specified length into the destination buffer.
+     *
+     * @param dest the destination byte buffer
+     * @param length the maximum length of the data to read
+     * @param timeout the timeout for reading in milliseconds, 0 is infinite
+     * @return the actual number of bytes read
+     * @throws IOException if an error occurred during reading
+     */
+    int read(final byte[] dest, int length, final int timeout) throws IOException;
 
     /**
      * Writes as many bytes as possible from the source buffer.
      *
      * @param src the source byte buffer
      * @param timeout the timeout for writing in milliseconds, 0 is infinite
-     * @return the actual number of bytes written
+     * @throws SerialTimeoutException if timeout reached before sending all data.
+     *                                ex.bytesTransferred may contain bytes transferred
      * @throws IOException if an error occurred during writing
      */
-    public int write(final byte[] src, final int timeout) throws IOException;
+    void write(final byte[] src, final int timeout) throws IOException;
+
+    /**
+     * Writes bytes with specified length from the source buffer.
+     *
+     * @param src the source byte buffer
+     * @param length the length of the data to write
+     * @param timeout the timeout for writing in milliseconds, 0 is infinite
+     * @throws SerialTimeoutException if timeout reached before sending all data.
+     *                                ex.bytesTransferred may contain bytes transferred
+     * @throws IOException if an error occurred during writing
+     */
+    void write(final byte[] src, int length, final int timeout) throws IOException;
 
     /**
      * Sets various serial port parameters.
@@ -145,9 +175,9 @@ public interface UsbSerialPort extends Closeable {
      * @param parity one of {@link #PARITY_NONE}, {@link #PARITY_ODD},
      *               {@link #PARITY_EVEN}, {@link #PARITY_MARK}, or {@link #PARITY_SPACE}.
      * @throws IOException on error setting the port parameters
-     * @throws UnsupportedOperationException if values are not supported by a specific device
+     * @throws UnsupportedOperationException if not supported or values are not supported by a specific device
      */
-    public void setParameters(int baudRate, int dataBits, int stopBits, int parity) throws IOException;
+    void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException;
 
     /**
      * Gets the CD (Carrier Detect) bit from the underlying UART.
@@ -156,7 +186,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getCD() throws IOException;
+    boolean getCD() throws IOException;
 
     /**
      * Gets the CTS (Clear To Send) bit from the underlying UART.
@@ -165,7 +195,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getCTS() throws IOException;
+    boolean getCTS() throws IOException;
 
     /**
      * Gets the DSR (Data Set Ready) bit from the underlying UART.
@@ -174,7 +204,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getDSR() throws IOException;
+    boolean getDSR() throws IOException;
 
     /**
      * Gets the DTR (Data Terminal Ready) bit from the underlying UART.
@@ -183,7 +213,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getDTR() throws IOException;
+    boolean getDTR() throws IOException;
 
     /**
      * Sets the DTR (Data Terminal Ready) bit on the underlying UART, if supported.
@@ -192,7 +222,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during writing
      * @throws UnsupportedOperationException if not supported
      */
-    public void setDTR(boolean value) throws IOException;
+    void setDTR(boolean value) throws IOException;
 
     /**
      * Gets the RI (Ring Indicator) bit from the underlying UART.
@@ -201,7 +231,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getRI() throws IOException;
+    boolean getRI() throws IOException;
 
     /**
      * Gets the RTS (Request To Send) bit from the underlying UART.
@@ -210,7 +240,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during reading
      * @throws UnsupportedOperationException if not supported
      */
-    public boolean getRTS() throws IOException;
+    boolean getRTS() throws IOException;
 
     /**
      * Sets the RTS (Request To Send) bit on the underlying UART, if supported.
@@ -219,7 +249,7 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during writing
      * @throws UnsupportedOperationException if not supported
      */
-    public void setRTS(boolean value) throws IOException;
+    void setRTS(boolean value) throws IOException;
 
     /**
      * Gets all control line values from the underlying UART, if supported.
@@ -227,8 +257,9 @@ public interface UsbSerialPort extends Closeable {
      *
      * @return EnumSet.contains(...) is {@code true} if set, else {@code false}
      * @throws IOException if an error occurred during reading
+     * @throws UnsupportedOperationException if not supported
      */
-    public EnumSet<ControlLine> getControlLines() throws IOException;
+    EnumSet<ControlLine> getControlLines() throws IOException;
 
     /**
      * Gets all control line supported flags.
@@ -236,7 +267,37 @@ public interface UsbSerialPort extends Closeable {
      * @return EnumSet.contains(...) is {@code true} if supported, else {@code false}
      * @throws IOException if an error occurred during reading
      */
-    public EnumSet<ControlLine> getSupportedControlLines() throws IOException;
+    EnumSet<ControlLine> getSupportedControlLines() throws IOException;
+
+    /**
+     * Set flow control mode, if supported
+     * @param flowControl @FlowControl
+     * @throws IOException if an error occurred during writing
+     * @throws UnsupportedOperationException if not supported
+     */
+    void setFlowControl(FlowControl flowControl) throws IOException;
+
+    /**
+     * Get flow control mode.
+     * @return FlowControl
+     */
+    FlowControl getFlowControl();
+
+    /**
+     * Get supported flow control modes
+     * @return EnumSet.contains(...) is {@code true} if supported, else {@code false}
+     */
+    EnumSet<FlowControl> getSupportedFlowControl();
+
+    /**
+     * If flow control = XON_XOFF, indicates that send is enabled by XON.
+     * Devices supporting flow control = XON_XOFF_INLINE return CHAR_XON/CHAR_XOFF in read() data.
+     *
+     * @return the current state
+     * @throws IOException if an error occurred during reading
+     * @throws UnsupportedOperationException if not supported
+     */
+    boolean getXON() throws IOException;
 
     /**
      * Purge non-transmitted output data and / or non-read input data.
@@ -246,11 +307,18 @@ public interface UsbSerialPort extends Closeable {
      * @throws IOException if an error occurred during flush
      * @throws UnsupportedOperationException if not supported
      */
-    public void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException;
+    void purgeHwBuffers(boolean purgeWriteBuffers, boolean purgeReadBuffers) throws IOException;
+
+    /**
+     * send BREAK condition.
+     *
+     * @param value set/reset
+     */
+    void setBreak(boolean value) throws IOException;
 
     /**
      * Returns the current state of the connection.
      */
-    public boolean isOpen();
+    boolean isOpen();
 
 }

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/UsbSerialProber.java

@@ -37,6 +37,8 @@ public class UsbSerialProber {
         probeTable.addDriver(FtdiSerialDriver.class);
         probeTable.addDriver(ProlificSerialDriver.class);
         probeTable.addDriver(Ch34xSerialDriver.class);
+        probeTable.addDriver(GsmModemSerialDriver.class);
+        probeTable.addDriver(ChromeCcdSerialDriver.class);
         return probeTable;
     }
 
@@ -46,11 +48,11 @@ public class UsbSerialProber {
      * not require permission from the Android USB system, since it does not
      * open any of the devices.
      *
-     * @param usbManager
+     * @param usbManager usb manager
      * @return a list, possibly empty, of all compatible drivers
      */
     public List<UsbSerialDriver> findAllDrivers(final UsbManager usbManager) {
-        final List<UsbSerialDriver> result = new ArrayList<UsbSerialDriver>();
+        final List<UsbSerialDriver> result = new ArrayList<>();
 
         for (final UsbDevice usbDevice : usbManager.getDeviceList().values()) {
             final UsbSerialDriver driver = probeDevice(usbDevice);
@@ -69,11 +71,7 @@ public class UsbSerialProber {
      *         {@code null} if none available.
      */
     public UsbSerialDriver probeDevice(final UsbDevice usbDevice) {
-        final int vendorId = usbDevice.getVendorId();
-        final int productId = usbDevice.getProductId();
-
-        final Class<? extends UsbSerialDriver> driverClass =
-                mProbeTable.findDriver(vendorId, productId);
+        final Class<? extends UsbSerialDriver> driverClass = mProbeTable.findDriver(usbDevice);
         if (driverClass != null) {
             final UsbSerialDriver driver;
             try {

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/HexDump.java

@@ -19,14 +19,17 @@ package com.hoho.android.usbserial.util;
 import java.security.InvalidParameterException;
 
 /**
- * Clone of Android's HexDump class, for use in debugging. Cosmetic changes
- * only.
+ * Clone of Android's /core/java/com/android/internal/util/HexDump class, for use in debugging.
+ * Changes: space separated hex strings
  */
 public class HexDump {
     private final static char[] HEX_DIGITS = {
             '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
     };
 
+    private HexDump() {
+    }
+
     public static String dumpHexString(byte[] array) {
         return dumpHexString(array, 0, array.length);
     }
@@ -82,10 +85,12 @@ public class HexDump {
     }
 
     public static String toHexString(byte[] array, int offset, int length) {
-        char[] buf = new char[length * 2];
+        char[] buf = new char[length > 0 ? length * 3 - 1 : 0];
 
         int bufIndex = 0;
         for (int i = offset; i < offset + length; i++) {
+            if (i > offset)
+                buf[bufIndex++] = ' ';
             byte b = array[i];
             buf[bufIndex++] = HEX_DIGITS[(b >>> 4) & 0x0F];
             buf[bufIndex++] = HEX_DIGITS[b & 0x0F];
@@ -139,13 +144,13 @@ public class HexDump {
         throw new InvalidParameterException("Invalid hex char '" + c + "'");
     }
 
+    /** accepts any separator, e.g. space or newline */
     public static byte[] hexStringToByteArray(String hexString) {
         int length = hexString.length();
-        byte[] buffer = new byte[length / 2];
+        byte[] buffer = new byte[(length + 1) / 3];
 
-        for (int i = 0; i < length; i += 2) {
-            buffer[i / 2] = (byte) ((toByte(hexString.charAt(i)) << 4) | toByte(hexString
-                    .charAt(i + 1)));
+        for (int i = 0; i < length; i += 3) {
+            buffer[i / 3] = (byte) ((toByte(hexString.charAt(i)) << 4) | toByte(hexString.charAt(i + 1)));
         }
 
         return buffer;

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/MonotonicClock.java

@@ -0,0 +1,14 @@
+package com.hoho.android.usbserial.util;
+
+public final class MonotonicClock {
+
+    private static final long NS_PER_MS = 1_000_000;
+
+    private MonotonicClock() {
+    }
+
+    public static long millis() {
+        return System.nanoTime() / NS_PER_MS;
+    }
+
+}

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/SerialInputOutputManager.java

@@ -6,40 +6,47 @@
 
 package com.hoho.android.usbserial.util;
 
+import android.os.Process;
 import android.util.Log;
 
 import com.hoho.android.usbserial.driver.UsbSerialPort;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
- * Utility class which services a {@link UsbSerialPort} in its {@link #run()} method.
+ * Utility class which services a {@link UsbSerialPort} in its {@link #runWrite()} ()} and {@link #runRead()} ()} ()} methods.
  *
  * @author mike wakerly (opensource@hoho.com)
  */
-public class SerialInputOutputManager implements Runnable {
-
-    private static final String TAG = SerialInputOutputManager.class.getSimpleName();
-    private static final boolean DEBUG = true;
-    private static final int BUFSIZ = 4096;
-
-    /**
-     * default read timeout is infinite, to avoid data loss with bulkTransfer API
-     */
-    private int mReadTimeout = 0;
-    private int mWriteTimeout = 0;
-
-    private final ByteBuffer mReadBuffer = ByteBuffer.allocate(BUFSIZ);
-    private final ByteBuffer mWriteBuffer = ByteBuffer.allocate(BUFSIZ); // Synchronized by 'mWriteBuffer'
+public class SerialInputOutputManager {
 
     public enum State {
         STOPPED,
+        STARTING,
         RUNNING,
         STOPPING
     }
 
-    private State mState = State.STOPPED; // Synchronized by 'this'
+    public static boolean DEBUG = false;
+
+    private static final String TAG = SerialInputOutputManager.class.getSimpleName();
+    private static final int BUFSIZ = 4096;
+
+    private int mReadTimeout = 0;
+    private int mWriteTimeout = 0;
+
+    private final Object mReadBufferLock = new Object();
+    private final Object mWriteBufferLock = new Object();
+
+    private ByteBuffer mReadBuffer; // default size = getReadEndpoint().getMaxPacketSize()
+    private ByteBuffer mWriteBuffer = ByteBuffer.allocate(BUFSIZ);
+
+    private int mThreadPriority = Process.THREAD_PRIORITY_URGENT_AUDIO;
+    private final AtomicReference<State> mState = new AtomicReference<>(State.STOPPED);
+    private CountDownLatch mStartuplatch = new CountDownLatch(2);
     private Listener mListener; // Synchronized by 'this'
     private final UsbSerialPort mSerialPort;
 
@@ -47,21 +54,23 @@ public class SerialInputOutputManager implements Runnable {
         /**
          * Called when new incoming data is available.
          */
-        public void onNewData(byte[] data);
+        void onNewData(byte[] data);
 
         /**
-         * Called when {@link SerialInputOutputManager#run()} aborts due to an error.
+         * Called when {@link SerialInputOutputManager#runRead()} ()} or {@link SerialInputOutputManager#runWrite()} ()} ()} aborts due to an error.
          */
-        public void onRunError(Exception e);
+        void onRunError(Exception e);
     }
 
     public SerialInputOutputManager(UsbSerialPort serialPort) {
         mSerialPort = serialPort;
+        mReadBuffer = ByteBuffer.allocate(serialPort.getReadEndpoint().getMaxPacketSize());
     }
 
     public SerialInputOutputManager(UsbSerialPort serialPort, Listener listener) {
         mSerialPort = serialPort;
         mListener = listener;
+        mReadBuffer = ByteBuffer.allocate(serialPort.getReadEndpoint().getMaxPacketSize());
     }
 
     public synchronized void setListener(Listener listener) {
@@ -72,10 +81,25 @@ public class SerialInputOutputManager implements Runnable {
         return mListener;
     }
 
+    /**
+     * setThreadPriority. By default a higher priority than UI thread is used to prevent data loss
+     *
+     * @param threadPriority  see {@link Process#setThreadPriority(int)}
+     * */
+    public void setThreadPriority(int threadPriority) {
+        if (!mState.compareAndSet(State.STOPPED, State.STOPPED)) {
+            throw new IllegalStateException("threadPriority only configurable before SerialInputOutputManager is started");
+        }
+        mThreadPriority = threadPriority;
+    }
+
+    /**
+     * read/write timeout
+     */
     public void setReadTimeout(int timeout) {
         // when set if already running, read already blocks and the new value will not become effective now
-        if(mReadTimeout == 0 && timeout != 0 && mState != State.STOPPED)
-            throw new IllegalStateException("Set readTimeout before SerialInputOutputManager is started");
+        if(mReadTimeout == 0 && timeout != 0 && mState.get() != State.STOPPED)
+            throw new IllegalStateException("readTimeout only configurable before SerialInputOutputManager is started");
         mReadTimeout = timeout;
     }
 
@@ -91,93 +115,222 @@ public class SerialInputOutputManager implements Runnable {
         return mWriteTimeout;
     }
 
-    /*
-     * when writeAsync is used, it is recommended to use readTimeout != 0,
-     * else the write will be delayed until read data is available
+    /**
+     * read/write buffer size
      */
-    public void writeAsync(byte[] data) {
-        synchronized (mWriteBuffer) {
-            mWriteBuffer.put(data);
+    public void setReadBufferSize(int bufferSize) {
+        if (getReadBufferSize() == bufferSize)
+            return;
+        synchronized (mReadBufferLock) {
+            mReadBuffer = ByteBuffer.allocate(bufferSize);
         }
     }
 
-    public synchronized void stop() {
-        if (getState() == State.RUNNING) {
-            Log.i(TAG, "Stop requested");
-            mState = State.STOPPING;
+    public int getReadBufferSize() {
+        return mReadBuffer.capacity();
+    }
+
+    public void setWriteBufferSize(int bufferSize) {
+        if(getWriteBufferSize() == bufferSize)
+            return;
+        synchronized (mWriteBufferLock) {
+            ByteBuffer newWriteBuffer = ByteBuffer.allocate(bufferSize);
+            if(mWriteBuffer.position() > 0)
+                newWriteBuffer.put(mWriteBuffer.array(), 0, mWriteBuffer.position());
+            mWriteBuffer = newWriteBuffer;
         }
     }
 
-    public synchronized State getState() {
-        return mState;
+    public int getWriteBufferSize() {
+        return mWriteBuffer.capacity();
     }
 
     /**
-     * Continuously services the read and write buffers until {@link #stop()} is
-     * called, or until a driver exception is raised.
+     * write data asynchronously
      */
-    @Override
-    public void run() {
-        synchronized (this) {
-            if (getState() != State.STOPPED) {
-                throw new IllegalStateException("Already running");
-            }
-            mState = State.RUNNING;
+    public void writeAsync(byte[] data) {
+        synchronized (mWriteBufferLock) {
+            mWriteBuffer.put(data);
+            mWriteBufferLock.notifyAll(); // Notify waiting threads
         }
+    }
 
-        Log.i(TAG, "Running ...");
-        try {
-            while (true) {
-                if (getState() != State.RUNNING) {
-                    Log.i(TAG, "Stopping mState=" + getState());
-                    break;
-                }
-                step();
+    /**
+     * start SerialInputOutputManager in separate threads
+     */
+    public void start() {
+        if(mState.compareAndSet(State.STOPPED, State.STARTING)) {
+            mStartuplatch = new CountDownLatch(2);
+            new Thread(this::runRead, this.getClass().getSimpleName() + "_read").start();
+            new Thread(this::runWrite, this.getClass().getSimpleName() + "_write").start();
+            try {
+                mStartuplatch.await();
+                mState.set(State.RUNNING);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
             }
-        } catch (Exception e) {
-            Log.w(TAG, "Run ending due to exception: " + e.getMessage(), e);
-            final Listener listener = getListener();
-            if (listener != null) {
-              listener.onRunError(e);
+        } else {
+            throw new IllegalStateException("already started");
+        }
+    }
+
+    /**
+     * stop SerialInputOutputManager threads
+     *
+     * when using readTimeout == 0 (default), additionally use usbSerialPort.close() to
+     * interrupt blocking read
+     */
+    public void stop() {
+        if(mState.compareAndSet(State.RUNNING, State.STOPPING)) {
+            synchronized (mWriteBufferLock) {
+                mWriteBufferLock.notifyAll(); // wake up write thread to check the stop condition
             }
-        } finally {
-            synchronized (this) {
-                mState = State.STOPPED;
-                Log.i(TAG, "Stopped");
+            Log.i(TAG, "Stop requested");
+        }
+    }
+
+    public State getState() {
+        return mState.get();
+    }
+
+    /**
+     * @return true if the thread is still running
+     */
+    private boolean isStillRunning() {
+        State state = mState.get();
+        return ((state == State.RUNNING) || (state == State.STARTING))
+            && !Thread.currentThread().isInterrupted();
+    }
+
+    /**
+     * Notify listener of an error
+     *
+     * @param e the exception
+     */
+    private void notifyErrorListener(Throwable e) {
+        Listener listener = getListener();
+        if (listener != null) {
+            try {
+                listener.onRunError(e instanceof Exception ? (Exception) e : new Exception(e));
+            } catch (Throwable t) {
+                Log.w(TAG, "Exception in onRunError: " + t.getMessage(), t);
             }
         }
     }
 
-    private void step() throws IOException {
+    /**
+     * Set the thread priority
+     */
+    private void setThreadPriority() {
+        if (mThreadPriority != Process.THREAD_PRIORITY_DEFAULT) {
+            Process.setThreadPriority(mThreadPriority);
+        }
+    }
+
+    /**
+     * Continuously services the read buffers until {@link #stop()} is called, or until a driver exception is
+     * raised.
+     */
+    void runRead() {
+        Log.i(TAG, "runRead running ...");
+        try {
+            setThreadPriority();
+            mStartuplatch.countDown();
+            do {
+                stepRead();
+            } while (isStillRunning());
+            Log.i(TAG, "runRead: Stopping mState=" + getState());
+        } catch (Throwable e) {
+            if (Thread.currentThread().isInterrupted()) {
+                Log.w(TAG, "runRead: interrupted");
+            } else if(mSerialPort.isOpen()) {
+                Log.w(TAG, "runRead ending due to exception: " + e.getMessage(), e);
+            } else {
+                Log.i(TAG, "runRead: Socket closed");
+            }
+            notifyErrorListener(e);
+        } finally {
+            if (mState.compareAndSet(State.RUNNING, State.STOPPING)) {
+                synchronized (mWriteBufferLock) {
+                    mWriteBufferLock.notifyAll(); // wake up write thread to check the stop condition
+                }
+            } else if (mState.compareAndSet(State.STOPPING, State.STOPPED)) {
+                Log.i(TAG, "runRead: Stopped mState=" + getState());
+            }
+        }
+    }
+
+    /**
+     * Continuously services the write buffers until {@link #stop()} is called, or until a driver exception is
+     * raised.
+     */
+    void runWrite() {
+        Log.i(TAG, "runWrite running ...");
+        try {
+            setThreadPriority();
+            mStartuplatch.countDown();
+            do {
+                stepWrite();
+            } while (isStillRunning());
+            Log.i(TAG, "runWrite: Stopping mState=" + getState());
+        } catch (Throwable e) {
+            if (Thread.currentThread().isInterrupted()) {
+                Log.w(TAG, "runWrite: interrupted");
+            } else if(mSerialPort.isOpen()) {
+                Log.w(TAG, "runWrite ending due to exception: " + e.getMessage(), e);
+            } else {
+                Log.i(TAG, "runWrite: Socket closed");
+            }
+            notifyErrorListener(e);
+        } finally {
+            if (!mState.compareAndSet(State.RUNNING, State.STOPPING)) {
+                if (mState.compareAndSet(State.STOPPING, State.STOPPED)) {
+                    Log.i(TAG, "runWrite: Stopped mState=" + getState());
+                }
+            }
+        }
+    }
+
+    private void stepRead() throws IOException {
         // Handle incoming data.
-        int len = mSerialPort.read(mReadBuffer.array(), mReadTimeout);
+        byte[] buffer;
+        synchronized (mReadBufferLock) {
+            buffer = mReadBuffer.array();
+        }
+        int len = mSerialPort.read(buffer, mReadTimeout);
         if (len > 0) {
-            if (DEBUG) Log.d(TAG, "Read data len=" + len);
+            if (DEBUG) {
+                Log.d(TAG, "Read data len=" + len);
+            }
             final Listener listener = getListener();
             if (listener != null) {
                 final byte[] data = new byte[len];
-                mReadBuffer.get(data, 0, len);
+                System.arraycopy(buffer, 0, data, 0, len);
                 listener.onNewData(data);
             }
-            mReadBuffer.clear();
         }
+    }
 
+    private void stepWrite() throws IOException, InterruptedException {
         // Handle outgoing data.
-        byte[] outBuff = null;
-        synchronized (mWriteBuffer) {
-            len = mWriteBuffer.position();
+        byte[] buffer = null;
+        synchronized (mWriteBufferLock) {
+            int len = mWriteBuffer.position();
             if (len > 0) {
-                outBuff = new byte[len];
+                buffer = new byte[len];
                 mWriteBuffer.rewind();
-                mWriteBuffer.get(outBuff, 0, len);
+                mWriteBuffer.get(buffer, 0, len);
                 mWriteBuffer.clear();
+                mWriteBufferLock.notifyAll(); // Notify writeAsync that there is space in the buffer
+            } else {
+                mWriteBufferLock.wait();
             }
         }
-        if (outBuff != null) {
+        if (buffer != null) {
             if (DEBUG) {
-                Log.d(TAG, "Writing data len=" + len);
+                Log.d(TAG, "Writing data len=" + buffer.length);
             }
-            mSerialPort.write(outBuff, mWriteTimeout);
+            mSerialPort.write(buffer, mWriteTimeout);
         }
     }
 

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/UsbUtils.java

@@ -0,0 +1,33 @@
+package com.hoho.android.usbserial.util;
+
+import android.hardware.usb.UsbDeviceConnection;
+
+import java.util.ArrayList;
+
+public class UsbUtils {
+
+    private UsbUtils() {
+    }
+
+    public static  ArrayList<byte[]> getDescriptors(UsbDeviceConnection connection) {
+        ArrayList<byte[]> descriptors = new ArrayList<>();
+        byte[] rawDescriptors = connection.getRawDescriptors();
+        if (rawDescriptors != null) {
+            int pos = 0;
+            while (pos < rawDescriptors.length) {
+                int len = rawDescriptors[pos] & 0xFF;
+                if (len == 0)
+                    break;
+                if (pos + len > rawDescriptors.length)
+                    len = rawDescriptors.length - pos;
+                byte[] descriptor = new byte[len];
+                System.arraycopy(rawDescriptors, pos, descriptor, 0, len);
+                descriptors.add(descriptor);
+                pos += len;
+            }
+        }
+        return descriptors;
+    }
+
+
+}

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/XonXoffFilter.java

@@ -0,0 +1,47 @@
+package com.hoho.android.usbserial.util;
+
+import com.hoho.android.usbserial.driver.UsbSerialPort;
+
+import java.io.IOException;
+
+/**
+ * Some devices return XON and XOFF characters inline in read() data.
+ * Other devices return XON / XOFF condition thru getXOFF() method.
+ */
+
+public class XonXoffFilter {
+    private boolean xon = true;
+
+    public XonXoffFilter() {
+    }
+
+    public boolean getXON()  {
+        return xon;
+    }
+
+    /**
+     * Filter XON/XOFF from read() data and remember
+     *
+     * @param data unfiltered data
+     * @return filtered data
+     */
+    public byte[] filter(byte[] data) {
+        int found = 0;
+        for (int i=0; i<data.length; i++) {
+            if (data[i] == UsbSerialPort.CHAR_XON || data[i] == UsbSerialPort.CHAR_XOFF)
+                found++;
+        }
+        if(found == 0)
+            return data;
+        byte[] filtered = new byte[data.length - found];
+        for (int i=0, j=0; i<data.length; i++) {
+            if (data[i] == UsbSerialPort.CHAR_XON)
+                xon = true;
+            else if(data[i] == UsbSerialPort.CHAR_XOFF)
+                xon = false;
+            else
+                filtered[j++] = data[i];
+        }
+        return filtered;
+    }
+}

usbSerialForAndroid/src/test/java/android/util/Log.java

@@ -0,0 +1,29 @@
+// without this class Mockito complains about non-mocked Log methods
+package android.util;
+
+public class Log {
+    public static int d(String tag, String msg) {
+        System.out.println("DEBUG: " + tag + ": " + msg);
+        return 0;
+    }
+
+    public static int i(String tag, String msg) {
+        System.out.println("INFO: " + tag + ": " + msg);
+        return 0;
+    }
+
+    public static int w(String tag, String msg) {
+        System.out.println("WARN: " + tag + ": " + msg);
+        return 0;
+    }
+
+    public static int w(String tag, String msg, Throwable tr) {
+        System.out.println("WARN: " + tag + ": " + msg + " / " + tr.getMessage());
+        return 0;
+    }
+
+    public static int e(String tag, String msg) {
+        System.out.println("ERROR: " + tag + ": " + msg);
+        return 0;
+    }
+}

usbSerialForAndroid/src/test/java/android/util/Pair.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.util;
+
+
+import androidx.annotation.Nullable;
+
+import java.util.Objects;
+
+/**
+ * Container to ease passing around a tuple of two objects. This object provides a sensible
+ * implementation of equals(), returning true if equals() is true on each of the contained
+ * objects.
+ */
+public class Pair<F, S> {
+    public final F first;
+    public final S second;
+
+    /**
+     * Constructor for a Pair.
+     *
+     * @param first the first object in the Pair
+     * @param second the second object in the pair
+     */
+    public Pair(F first, S second) {
+        this.first = first;
+        this.second = second;
+    }
+
+    /**
+     * Checks the two objects for equality by delegating to their respective
+     * {@link Object#equals(Object)} methods.
+     *
+     * @param o the {@link Pair} to which this one is to be checked for equality
+     * @return true if the underlying objects of the Pair are both considered
+     *         equal
+     */
+    @Override
+    public boolean equals(@Nullable Object o) {
+        if (!(o instanceof Pair)) {
+            return false;
+        }
+        Pair<?, ?> p = (Pair<?, ?>) o;
+        return Objects.equals(p.first, first) && Objects.equals(p.second, second);
+    }
+
+    /**
+     * Compute a hash code using the hash codes of the underlying objects
+     *
+     * @return a hashcode of the Pair
+     */
+    @Override
+    public int hashCode() {
+        return (first == null ? 0 : first.hashCode()) ^ (second == null ? 0 : second.hashCode());
+    }
+
+    @Override
+    public String toString() {
+        return "Pair{" + String.valueOf(first) + " " + String.valueOf(second) + "}";
+    }
+
+    /**
+     * Convenience method for creating an appropriately typed pair.
+     * @param a the first object in the Pair
+     * @param b the second object in the pair
+     * @return a Pair that is templatized with the types of a and b
+     */
+    public static <A, B> Pair <A, B> create(A a, B b) {
+        return new Pair<A, B>(a, b);
+    }
+}

usbSerialForAndroid/src/test/java/com/hoho/android/usbserial/driver/CdcAcmSerialDriverTest.java

@@ -0,0 +1,546 @@
+package com.hoho.android.usbserial.driver;
+
+import static com.hoho.android.usbserial.driver.CdcAcmSerialDriver.USB_SUBCLASS_ACM;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.mockito.Mockito.clearInvocations;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.hardware.usb.UsbConstants;
+import android.hardware.usb.UsbDevice;
+import android.hardware.usb.UsbDeviceConnection;
+import android.hardware.usb.UsbEndpoint;
+import android.hardware.usb.UsbInterface;
+
+import com.hoho.android.usbserial.util.HexDump;
+
+import org.junit.Test;
+
+import java.io.IOException;
+
+public class CdcAcmSerialDriverTest {
+
+    @Test
+    public void standardDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface controlInterface = mock(UsbInterface.class);
+        UsbInterface dataInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        /*
+         * digispark - no IAD
+         *   UsbInterface[mId=0,mAlternateSetting=0,mName=null,mClass=2,mSubclass=2,mProtocol=1,mEndpoints=[
+         *     UsbEndpoint[mAddress=131,mAttributes=3,mMaxPacketSize=8,mInterval=255]]
+         *   UsbInterface[mId=1,mAlternateSetting=0,mName=null,mClass=10,mSubclass=0,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=1,mAttributes=2,mMaxPacketSize=8,mInterval=0]
+         *     UsbEndpoint[mAddress=129,mAttributes=2,mMaxPacketSize=8,mInterval=0]]
+         */
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray(
+                "12 01 10 01 02 00 00 08 D0 16 7E 08 00 01 01 02 00 01\n" +
+                "09 02 43 00 02 01 00 80 32\n" +
+                "09 04 00 00 01 02 02 01 00\n" +
+                "05 24 00 10 01\n" +
+                "04 24 02 02\n" +
+                "05 24 06 00 01\n" +
+                "05 24 01 03 01\n" +
+                "07 05 83 03 08 00 FF\n" +
+                "09 04 01 00 02 0A 00 00 00\n" +
+                "07 05 01 02 08 00 00\n" +
+                "07 05 81 02 08 00 00"));
+        when(usbDeviceConnection.claimInterface(controlInterface,true)).thenReturn(true);
+        when(usbDeviceConnection.claimInterface(dataInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(2);
+        when(usbDevice.getInterface(0)).thenReturn(controlInterface);
+        when(usbDevice.getInterface(1)).thenReturn(dataInterface);
+        when(controlInterface.getId()).thenReturn(0);
+        when(controlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(controlInterface.getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+        when(controlInterface.getEndpointCount()).thenReturn(1);
+        when(controlInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(dataInterface.getId()).thenReturn(1);
+        when(dataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(dataInterface.getEndpointCount()).thenReturn(2);
+        when(dataInterface.getEndpoint(0)).thenReturn(writeEndpoint);
+        when(dataInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertEquals(readEndpoint, port.mReadEndpoint);
+        assertEquals(writeEndpoint, port.mWriteEndpoint);
+
+        ProbeTable probeTable = UsbSerialProber.getDefaultProbeTable();
+        Class<? extends UsbSerialDriver> probeDriver = probeTable.findDriver(usbDevice);
+        assertEquals(driver.getClass(), probeDriver);
+    }
+
+    @Test
+    public void singleInterfaceDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface usbInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        when(usbDeviceConnection.claimInterface(usbInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(1);
+        when(usbDevice.getInterface(0)).thenReturn(usbInterface);
+        when(usbInterface.getEndpointCount()).thenReturn(3);
+        when(usbInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(usbInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        when(usbInterface.getEndpoint(2)).thenReturn(writeEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertEquals(readEndpoint, port.mReadEndpoint);
+        assertEquals(writeEndpoint, port.mWriteEndpoint);
+
+        ProbeTable probeTable = UsbSerialProber.getDefaultProbeTable();
+        Class<? extends UsbSerialDriver> probeDriver = probeTable.findDriver(usbDevice);
+        assertNull(probeDriver);
+    }
+
+    @Test
+    public void multiPortDevice() throws Exception {
+        int n = 2;
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface[] controlInterfaces = new UsbInterface[n];
+        UsbInterface[] dataInterfaces = new UsbInterface[n];
+        UsbEndpoint[] controlEndpoints = new UsbEndpoint[n];
+        UsbEndpoint[] readEndpoints = new UsbEndpoint[n];
+        UsbEndpoint[] writeEndpoints = new UsbEndpoint[n];
+
+        /*
+         * pi zero - dual port
+         *   UsbInterface[mId=0,mAlternateSetting=0,mName=TinyUSB CDC,mClass=2,mSubclass=2,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=129,mAttributes=3,mMaxPacketSize=8,mInterval=16]]
+         *   UsbInterface[mId=1,mAlternateSetting=0,mName=null,mClass=10,mSubclass=0,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=2,mAttributes=2,mMaxPacketSize=64,mInterval=0]
+         *     UsbEndpoint[mAddress=130,mAttributes=2,mMaxPacketSize=64,mInterval=0]]
+         *   UsbInterface[mId=2,mAlternateSetting=0,mName=TinyUSB CDC,mClass=2,mSubclass=2,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=131,mAttributes=3,mMaxPacketSize=8,mInterval=16]]
+         *   UsbInterface[mId=3,mAlternateSetting=0,mName=null,mClass=10,mSubclass=0,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=4,mAttributes=2,mMaxPacketSize=64,mInterval=0]
+         *      UsbEndpoint[mAddress=132,mAttributes=2,mMaxPacketSize=64,mInterval=0]]
+         */
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray(
+                "12 01 00 02 EF 02 01 40 FE CA 02 40 00 01 01 02 03 01\n" +
+                "09 02 8D 00 04 01 00 80 32\n" +
+                "08 0B 00 02 02 02 00 00\n" +
+                "09 04 00 00 01 02 02 00 04\n" +
+                "05 24 00 20 01\n" +
+                "05 24 01 00 01\n" +
+                "04 24 02 02\n" +
+                "05 24 06 00 01\n" +
+                "07 05 81 03 08 00 10\n" +
+                "09 04 01 00 02 0A 00 00 00\n" +
+                "07 05 02 02 40 00 00\n" +
+                "07 05 82 02 40 00 00\n" +
+                "08 0B 02 02 02 02 00 00\n" +
+                "09 04 02 00 01 02 02 00 04\n" +
+                "05 24 00 20 01\n" +
+                "05 24 01 00 03\n" +
+                "04 24 02 02\n" +
+                "05 24 06 02 03\n" +
+                "07 05 83 03 08 00 10\n" +
+                "09 04 03 00 02 0A 00 00 00\n" +
+                "07 05 04 02 40 00 00\n" +
+                "07 05 84 02 40 00 00\n"));
+        when(usbDevice.getInterfaceCount()).thenReturn(2*n);
+        for(int i=0; i<n; i++) {
+            controlInterfaces[i] = mock(UsbInterface.class);
+            dataInterfaces[i] = mock(UsbInterface.class);
+            controlEndpoints[i] = mock(UsbEndpoint.class);
+            readEndpoints[i] = mock(UsbEndpoint.class);
+            writeEndpoints[i] = mock(UsbEndpoint.class);
+            when(usbDeviceConnection.claimInterface(controlInterfaces[i], true)).thenReturn(true);
+            when(usbDeviceConnection.claimInterface(dataInterfaces[i], true)).thenReturn(true);
+            when(usbDevice.getInterface(2*i  )).thenReturn(controlInterfaces[i]);
+            when(usbDevice.getInterface(2*i+1)).thenReturn(dataInterfaces[i]);
+            when(controlInterfaces[i].getId()).thenReturn(2*i);
+            when(controlInterfaces[i].getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+            when(controlInterfaces[i].getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+            when(controlInterfaces[i].getEndpointCount()).thenReturn(1);
+            when(controlInterfaces[i].getEndpoint(0)).thenReturn(controlEndpoints[i]);
+            when(dataInterfaces[i].getId()).thenReturn(2*i+1);
+            when(dataInterfaces[i].getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+            when(dataInterfaces[i].getEndpointCount()).thenReturn(2);
+            when(dataInterfaces[i].getEndpoint(0)).thenReturn(writeEndpoints[i]);
+            when(dataInterfaces[i].getEndpoint(1)).thenReturn(readEndpoints[i]);
+            when(controlEndpoints[i].getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+            when(controlEndpoints[i].getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+            when(readEndpoints[i].getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+            when(readEndpoints[i].getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+            when(writeEndpoints[i].getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+            when(writeEndpoints[i].getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        }
+        int i = 1;
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(i);
+        port.mConnection = usbDeviceConnection;
+        // reset invocations from countPorts()
+        clearInvocations(controlInterfaces[0]);
+        clearInvocations(controlInterfaces[1]);
+
+        port.openInt();
+        assertEquals(readEndpoints[i], port.mReadEndpoint);
+        assertEquals(writeEndpoints[i], port.mWriteEndpoint);
+        verify(controlInterfaces[0], times(0)).getInterfaceClass(); // not openInterface with 'no IAD fallback'
+        verify(controlInterfaces[1], times(2)).getInterfaceClass(); // openInterface with IAD
+        port.closeInt();
+        clearInvocations(controlInterfaces[0]);
+        clearInvocations(controlInterfaces[1]);
+
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(null);
+        port.openInt();
+        verify(controlInterfaces[0], times(2)).getInterfaceClass(); // openInterface with 'no IAD fallback'
+        verify(controlInterfaces[1], times(2)).getInterfaceClass(); // openInterface with 'no IAD fallback'
+        port.closeInt();
+        clearInvocations(controlInterfaces[0]);
+        clearInvocations(controlInterfaces[1]);
+
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray("01 02 02 82 02")); // truncated descriptor
+        port.openInt();
+        verify(controlInterfaces[0], times(2)).getInterfaceClass(); // openInterface with 'no IAD fallback'
+        verify(controlInterfaces[1], times(2)).getInterfaceClass(); // openInterface with 'no IAD fallback'
+    }
+
+    @Test
+    public void compositeDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface massStorageInterface = mock(UsbInterface.class);
+        UsbInterface controlInterface = mock(UsbInterface.class);
+        UsbInterface dataInterface = mock(UsbInterface.class);
+        UsbInterface hidInterface = mock(UsbInterface.class);
+        UsbInterface vendorInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        /*
+         * BBC micro:bit
+         *   UsbInterface[mId=0,mAlternateSetting=0,mName=USB_MSC,mClass=8,mSubclass=6,mProtocol=80,mEndpoints=[
+         *     UsbEndpoint[mAddress=130,mAttributes=2,mMaxPacketSize=64,mInterval=0]
+         *     UsbEndpoint[mAddress=2,mAttributes=2,mMaxPacketSize=64,mInterval=0]]
+         *   UsbInterface[mId=1,mAlternateSetting=0,mName=mbed Serial Port,mClass=2,mSubclass=2,mProtocol=1,mEndpoints=[
+         *     UsbEndpoint[mAddress=131,mAttributes=3,mMaxPacketSize=16,mInterval=32]]
+         *   UsbInterface[mId=2,mAlternateSetting=0,mName=mbed Serial Port,mClass=10,mSubclass=0,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=4,mAttributes=2,mMaxPacketSize=64,mInterval=0]
+         *     UsbEndpoint[mAddress=132,mAttributes=2,mMaxPacketSize=64,mInterval=0]]
+         *   UsbInterface[mId=3,mAlternateSetting=0,mName=CMSIS-DAP,mClass=3,mSubclass=0,mProtocol=0,mEndpoints=[
+         *     UsbEndpoint[mAddress=129,mAttributes=3,mMaxPacketSize=64,mInterval=1]
+         *     UsbEndpoint[mAddress=1,mAttributes=3,mMaxPacketSize=64,mInterval=1]]
+         *   UsbInterface[mId=4,mAlternateSetting=0,mName=WebUSB: CMSIS-DAP,mClass=255,mSubclass=3,mProtocol=0,mEndpoints=[]
+         */
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray(
+                "12 01 10 02 EF 02 01 40 28 0D 04 02 00 10 01 02 03 01\n" +
+                "09 02 8B 00 05 01 00 80 FA\n" +
+                "09 04 00 00 02 08 06 50 08\n" +
+                "07 05 82 02 40 00 00\n" +
+                "07 05 02 02 40 00 00\n" +
+                "08 0B 01 02 02 02 01 04\n" +
+                "09 04 01 00 01 02 02 01 04\n" +
+                "05 24 00 10 01\n" +
+                "05 24 01 03 02\n" +
+                "04 24 02 06\n" +
+                "05 24 06 01 02\n" +
+                "07 05 83 03 10 00 20\n" +
+                "09 04 02 00 02 0A 00 00 05\n" +
+                "07 05 04 02 40 00 00\n" +
+                "07 05 84 02 40 00 00\n" +
+                "09 04 03 00 02 03 00 00 06\n" +
+                "09 21 00 01 00 01 22 21 00\n" +
+                "07 05 81 03 40 00 01\n" +
+                "07 05 01 03 40 00 01\n" +
+                "09 04 04 00 00 FF 03 00 07"));
+        when(usbDeviceConnection.claimInterface(controlInterface,true)).thenReturn(true);
+        when(usbDeviceConnection.claimInterface(dataInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(5);
+        when(usbDevice.getInterface(0)).thenReturn(massStorageInterface);
+        when(usbDevice.getInterface(1)).thenReturn(controlInterface);
+        when(usbDevice.getInterface(2)).thenReturn(dataInterface);
+        when(usbDevice.getInterface(3)).thenReturn(hidInterface);
+        when(usbDevice.getInterface(4)).thenReturn(vendorInterface);
+        when(massStorageInterface.getId()).thenReturn(0);
+        when(massStorageInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_MASS_STORAGE);
+        when(controlInterface.getId()).thenReturn(1);
+        when(controlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(controlInterface.getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+        when(dataInterface.getId()).thenReturn(2);
+        when(dataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(hidInterface.getId()).thenReturn(3);
+        when(hidInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_HID);
+        when(vendorInterface.getId()).thenReturn(4);
+        when(vendorInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_VENDOR_SPEC);
+
+        when(controlInterface.getEndpointCount()).thenReturn(1);
+        when(controlInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(dataInterface.getEndpointCount()).thenReturn(2);
+        when(dataInterface.getEndpoint(0)).thenReturn(writeEndpoint);
+        when(dataInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertEquals(readEndpoint, port.mReadEndpoint);
+        assertEquals(writeEndpoint, port.mWriteEndpoint);
+
+        ProbeTable probeTable = UsbSerialProber.getDefaultProbeTable();
+        Class<? extends UsbSerialDriver> probeDriver = probeTable.findDriver(usbDevice);
+        assertEquals(driver.getClass(), probeDriver);
+    }
+
+    @Test
+    public void compositeRndisDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface rndisControlInterface = mock(UsbInterface.class);
+        UsbInterface rndisDataInterface = mock(UsbInterface.class);
+        UsbInterface controlInterface = mock(UsbInterface.class);
+        UsbInterface dataInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        // has multiple USB_CLASS_CDC_DATA interfaces => get correct with IAD
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray(
+                "12 01 00 02 EF 02 01 40 FE CA 02 40 00 01 01 02 03 01\n" +
+                "09 02 8D 00 04 01 00 80 32\n" +
+                "08 0B 00 02 E0 01 03 00\n" +
+                "09 04 00 00 01 E0 01 03 04\n" +
+                "05 24 00 10 01\n" +
+                "05 24 01 00 01\n" +
+                "04 24 02 00\n" +
+                "05 24 06 00 01\n" +
+                "07 05 81 03 08 00 01\n" +
+                "09 04 01 00 02 0A 00 00 00\n" +
+                "07 05 82 02 40 00 00\n" +
+                "07 05 02 02 40 00 00\n" +
+                "08 0B 02 02 02 02 00 00\n" +
+                "09 04 02 00 01 02 02 00 04\n" +
+                "05 24 00 20 01\n" +
+                "05 24 01 00 03\n" +
+                "04 24 02 02\n" +
+                "05 24 06 02 03\n" +
+                "07 05 83 03 08 00 10\n" +
+                "09 04 03 00 02 0A 00 00 00\n" +
+                "07 05 04 02 40 00 00\n" +
+                "07 05 84 02 40 00 00"));
+        when(usbDeviceConnection.claimInterface(controlInterface,true)).thenReturn(true);
+        when(usbDeviceConnection.claimInterface(dataInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(4);
+        when(usbDevice.getInterface(0)).thenReturn(rndisControlInterface);
+        when(usbDevice.getInterface(1)).thenReturn(rndisDataInterface);
+        when(usbDevice.getInterface(2)).thenReturn(controlInterface);
+        when(usbDevice.getInterface(3)).thenReturn(dataInterface);
+        when(rndisControlInterface.getId()).thenReturn(0);
+        when(rndisControlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_WIRELESS_CONTROLLER);
+        when(rndisControlInterface.getInterfaceSubclass()).thenReturn(1);
+        when(rndisControlInterface.getInterfaceProtocol()).thenReturn(3);
+        when(rndisDataInterface.getId()).thenReturn(1);
+        when(rndisDataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(controlInterface.getId()).thenReturn(2);
+        when(controlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(controlInterface.getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+        when(dataInterface.getId()).thenReturn(3);
+        when(dataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+
+        when(controlInterface.getEndpointCount()).thenReturn(1);
+        when(controlInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(dataInterface.getEndpointCount()).thenReturn(2);
+        when(dataInterface.getEndpoint(0)).thenReturn(writeEndpoint);
+        when(dataInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertEquals(readEndpoint, port.mReadEndpoint);
+        assertEquals(writeEndpoint, port.mWriteEndpoint);
+    }
+
+    @Test
+    public void compositeAlternateSettingDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface ethernetControlInterface = mock(UsbInterface.class);
+        UsbInterface ethernetDummyInterface = mock(UsbInterface.class);
+        UsbInterface ethernetDataInterface = mock(UsbInterface.class);
+        UsbInterface controlInterface = mock(UsbInterface.class);
+        UsbInterface dataInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        // has multiple USB_CLASS_CDC_DATA interfaces => get correct with IAD
+        when(usbDeviceConnection.getRawDescriptors()).thenReturn(HexDump.hexStringToByteArray(
+                "12 01 00 02 EF 02 01 40 FE CA 02 40 00 01 01 02 03 01\n" +
+                "09 02 9A 00 04 01 00 80 32\n" +
+                "08 0B 00 02 02 06 00 00\n" +
+                "09 04 00 00 01 02 06 00 04\n" +
+                "05 24 00 20 01\n" +
+                "05 24 06 00 01\n" +
+                "0D 24 0F 04 00 00 00 00 DC 05 00 00 00\n" +
+                "07 05 81 03 08 00 01\n" +
+                "09 04 01 00 00 0A 00 00 00\n" +
+                "09 04 01 01 02 0A 00 00 00\n" +
+                "07 05 82 02 40 00 00\n" +
+                "07 05 02 02 40 00 00\n" +
+                "08 0B 02 02 02 02 00 00\n" +
+                "09 04 02 00 01 02 02 00 04\n" +
+                "05 24 00 20 01\n" +
+                "05 24 01 00 03\n" +
+                "04 24 02 02\n" +
+                "05 24 06 02 03\n" +
+                "07 05 83 03 08 00 10\n" +
+                "09 04 03 00 02 0A 00 00 00\n" +
+                "07 05 04 02 40 00 00\n" +
+                "07 05 84 02 40 00 00"));
+        when(usbDeviceConnection.claimInterface(controlInterface,true)).thenReturn(true);
+        when(usbDeviceConnection.claimInterface(dataInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(5);
+        when(usbDevice.getInterface(0)).thenReturn(ethernetControlInterface);
+        when(usbDevice.getInterface(1)).thenReturn(ethernetDummyInterface);
+        when(usbDevice.getInterface(2)).thenReturn(ethernetDataInterface);
+        when(usbDevice.getInterface(3)).thenReturn(controlInterface);
+        when(usbDevice.getInterface(4)).thenReturn(dataInterface);
+        when(ethernetControlInterface.getId()).thenReturn(0);
+        when(ethernetControlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(ethernetControlInterface.getInterfaceSubclass()).thenReturn(6);
+        when(ethernetDummyInterface.getId()).thenReturn(1);
+        when(ethernetDummyInterface.getAlternateSetting()).thenReturn(0);
+        when(ethernetDummyInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(ethernetDataInterface.getId()).thenReturn(1);
+        when(ethernetDataInterface.getAlternateSetting()).thenReturn(1);
+        when(ethernetDataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(controlInterface.getId()).thenReturn(2);
+        when(controlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(controlInterface.getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+        when(dataInterface.getId()).thenReturn(3);
+        when(dataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+
+        when(controlInterface.getEndpointCount()).thenReturn(1);
+        when(controlInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(dataInterface.getEndpointCount()).thenReturn(2);
+        when(dataInterface.getEndpoint(0)).thenReturn(writeEndpoint);
+        when(dataInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertEquals(readEndpoint, port.mReadEndpoint);
+        assertEquals(writeEndpoint, port.mWriteEndpoint);
+    }
+
+    @Test
+    public void invalidStandardDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface controlInterface = mock(UsbInterface.class);
+        UsbInterface dataInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        when(usbDeviceConnection.claimInterface(controlInterface,true)).thenReturn(true);
+        when(usbDeviceConnection.claimInterface(dataInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(2);
+        when(usbDevice.getInterface(0)).thenReturn(controlInterface);
+        when(usbDevice.getInterface(1)).thenReturn(dataInterface);
+        when(controlInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_COMM);
+        when(controlInterface.getInterfaceSubclass()).thenReturn(USB_SUBCLASS_ACM);
+        when(controlInterface.getEndpointCount()).thenReturn(1);
+        when(controlInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(dataInterface.getInterfaceClass()).thenReturn(UsbConstants.USB_CLASS_CDC_DATA);
+        when(dataInterface.getEndpointCount()).thenReturn(2);
+        when(dataInterface.getEndpoint(0)).thenReturn(writeEndpoint);
+        when(dataInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        //when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        //when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        assertThrows(IOException.class, port::openInt);
+    }
+
+    @Test
+    public void invalidSingleInterfaceDevice() throws Exception {
+        UsbDeviceConnection usbDeviceConnection = mock(UsbDeviceConnection.class);
+        UsbDevice usbDevice = mock(UsbDevice.class);
+        UsbInterface usbInterface = mock(UsbInterface.class);
+        UsbEndpoint controlEndpoint = mock(UsbEndpoint.class);
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        //UsbEndpoint writeEndpoint = mock(UsbEndpoint.class);
+
+        when(usbDeviceConnection.claimInterface(usbInterface,true)).thenReturn(true);
+        when(usbDevice.getInterfaceCount()).thenReturn(1);
+        when(usbDevice.getInterface(0)).thenReturn(usbInterface);
+        when(usbInterface.getEndpointCount()).thenReturn(2);
+        when(usbInterface.getEndpoint(0)).thenReturn(controlEndpoint);
+        when(usbInterface.getEndpoint(1)).thenReturn(readEndpoint);
+        //when(usbInterface.getEndpoint(2)).thenReturn(writeEndpoint);
+        when(controlEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(controlEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_INT);
+        when(readEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_IN);
+        when(readEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+        //when(writeEndpoint.getDirection()).thenReturn(UsbConstants.USB_DIR_OUT);
+        //when(writeEndpoint.getType()).thenReturn(UsbConstants.USB_ENDPOINT_XFER_BULK);
+
+        CdcAcmSerialDriver driver = new CdcAcmSerialDriver(usbDevice);
+        CdcAcmSerialDriver.CdcAcmSerialPort port = (CdcAcmSerialDriver.CdcAcmSerialPort) driver.getPorts().get(0);
+        port.mConnection = usbDeviceConnection;
+        port.openInt();
+        assertNull(port.mWriteEndpoint);
+    }
+
+}

usbSerialForAndroid/src/test/java/com/hoho/android/usbserial/driver/FtdiSerialDriverTest.java

@@ -0,0 +1,89 @@
+package com.hoho.android.usbserial.driver;
+
+import android.hardware.usb.UsbDevice;
+import android.hardware.usb.UsbEndpoint;
+
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class FtdiSerialDriverTest {
+
+    private final UsbDevice usbDevice = mock(UsbDevice.class);
+    private final UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+
+    private void initBuf(byte[] buf) {
+        for(int i=0; i<buf.length; i++)
+            buf[i] = (byte) i;
+    }
+    private boolean testBuf(byte[] buf, int len) {
+        byte j = 2;
+        for(int i=0; i<len; i++) {
+            if(buf[i]!=j)
+                return false;
+            j++;
+            if(j % 64 == 0)
+                j+=2;
+        }
+        return true;
+    }
+
+    @Test
+    public void readFilter() throws Exception {
+        byte[] buf = new byte[2048];
+        int len;
+
+        when(usbDevice.getInterfaceCount()).thenReturn(1);
+        when(readEndpoint.getMaxPacketSize()).thenReturn(64);
+        FtdiSerialDriver driver = new FtdiSerialDriver(usbDevice);
+        FtdiSerialDriver.FtdiSerialPort port = (FtdiSerialDriver.FtdiSerialPort) driver.getPorts().get(0);
+        port.mReadEndpoint = readEndpoint;
+
+        len = port.readFilter(buf, 0);
+        assertEquals(len, 0);
+
+        assertThrows(IOException.class, () -> port.readFilter(buf, 1));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 2);
+        assertEquals(len, 0);
+
+        initBuf(buf);
+        len = port.readFilter(buf, 3);
+        assertEquals(len, 1);
+        assertTrue(testBuf(buf, len));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 4);
+        assertEquals(len, 2);
+        assertTrue(testBuf(buf, len));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 64);
+        assertEquals(len, 62);
+        assertTrue(testBuf(buf, len));
+
+        assertThrows(IOException.class, () -> port.readFilter(buf, 65));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 66);
+        assertEquals(len, 62);
+        assertTrue(testBuf(buf, len));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 68);
+        assertEquals(len, 64);
+        assertTrue(testBuf(buf, len));
+
+        initBuf(buf);
+        len = port.readFilter(buf, 16*64+11);
+        assertEquals(len, 16*62+9);
+        assertTrue(testBuf(buf, len));
+    }
+}

usbSerialForAndroid/src/test/java/com/hoho/android/usbserial/util/HexDumpText.java

@@ -0,0 +1,44 @@
+package com.hoho.android.usbserial.util;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import org.junit.Test;
+
+import java.security.InvalidParameterException;
+
+public class HexDumpText {
+
+    @Test
+    public void toByteArray() throws Exception {
+        assertThat(HexDump.toByteArray((byte)0x4a), equalTo(new byte[]{ 0x4A}));
+        assertThat(HexDump.toByteArray((short)0x4a5b), equalTo(new byte[]{ 0x4A, 0x5B}));
+        assertThat(HexDump.toByteArray((int)0x4a5b6c7d), equalTo(new byte[]{ 0x4A, 0x5B, 0x6C, 0x7D}));
+    }
+
+    @Test
+    public void toHexString() throws Exception {
+        assertEquals("4A", HexDump.toHexString((byte)0x4a));
+        assertEquals("4A 5B", HexDump.toHexString((short)0x4a5b));
+        assertEquals("4A 5B 6C 7D", HexDump.toHexString((int)0x4a5b6c7d));
+        assertEquals("4A 5B 6C 7D", HexDump.toHexString(new byte[]{ 0x4A, 0x5B, 0x6C, 0x7D}));
+        assertEquals("5B 6C", HexDump.toHexString(new byte[]{ 0x4A, 0x5B, 0x6C, 0x7D}, 1, 2));
+    }
+
+    @Test
+    public void dumpHexString() throws Exception {
+        assertEquals("10 31 32 33 34 35 36 37 .1234567\n18 39                   .9", HexDump.dumpHexString(new byte[]{ 0x10, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x18, 0x39}));
+        assertEquals("31 32                   12", HexDump.dumpHexString(new byte[]{ 0x30, 0x31, 0x32, 0x33}, 1, 2));
+    }
+
+    @Test
+    public void toByte() throws Exception {
+        assertThat(HexDump.hexStringToByteArray("4a 5B-6c\n7d"), equalTo(new byte[]{ 0x4A, 0x5B, 0x6C, 0x7D}));
+        assertThrows(InvalidParameterException.class, () -> HexDump.hexStringToByteArray("3 "));
+        assertThrows(InvalidParameterException.class, () -> HexDump.hexStringToByteArray("3z"));
+        assertThrows(InvalidParameterException.class, () -> HexDump.hexStringToByteArray("3Z"));
+    }
+
+}

usbSerialForAndroid/src/test/java/com/hoho/android/usbserial/util/SerialInputOutputManagerTest.java

@@ -0,0 +1,55 @@
+package com.hoho.android.usbserial.util;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import android.hardware.usb.UsbEndpoint;
+import android.os.Process;
+
+import com.hoho.android.usbserial.driver.CommonUsbSerialPort;
+
+import org.junit.Test;
+
+public class SerialInputOutputManagerTest {
+
+
+    // catch all Throwables in onNewData() and onRunError()
+    @Test
+    public void throwable() throws Exception {
+
+        class ExceptionListener implements SerialInputOutputManager.Listener {
+            public Exception e;
+            @Override public void onNewData(byte[] data) { throw new RuntimeException("exception1"); }
+            @Override public void onRunError(Exception e) { this.e = e; throw new RuntimeException("exception2"); }
+        }
+        class ErrorListener implements SerialInputOutputManager.Listener {
+            public Exception e;
+            @Override public void onNewData(byte[] data) { throw new UnknownError("error1"); }
+            @Override public void onRunError(Exception e) { this.e = e; throw new UnknownError("error2");}
+        }
+
+        UsbEndpoint readEndpoint = mock(UsbEndpoint.class);
+        when(readEndpoint.getMaxPacketSize()).thenReturn(16);
+        CommonUsbSerialPort port = mock(CommonUsbSerialPort.class);
+        when(port.getReadEndpoint()).thenReturn(readEndpoint);
+        when(port.read(new byte[16], 0)).thenReturn(1);
+        when(port.isOpen()).thenReturn(true);
+        SerialInputOutputManager manager = new SerialInputOutputManager(port);
+        manager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
+
+        ExceptionListener exceptionListener = new ExceptionListener();
+        manager.setListener(exceptionListener);
+        manager.runRead();
+        assertEquals(RuntimeException.class, exceptionListener.e.getClass());
+        assertEquals("exception1", exceptionListener.e.getMessage());
+
+        ErrorListener errorListener = new ErrorListener();
+        manager.setListener(errorListener);
+        manager.runRead();
+        assertEquals(Exception.class, errorListener.e.getClass());
+        assertEquals("java.lang.UnknownError: error1", errorListener.e.getMessage());
+        assertEquals(UnknownError.class, errorListener.e.getCause().getClass());
+        assertEquals("error1", errorListener.e.getCause().getMessage());
+    }
+}