.idea/AndroidProjectSystem.xml

@@ -1,6 +0,0 @@
-<?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

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="CompilerConfiguration">
-    <bytecodeTargetLevel target="21" />
+    <bytecodeTargetLevel target="17" />
   </component>
 </project>

.idea/misc.xml

@@ -1,4 +1,3 @@
-<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="NullableNotNullManager">
@@ -6,7 +5,7 @@
     <option name="myDefaultNotNull" value="androidx.annotation.NonNull" />
     <option name="myNullables">
       <value>
-        <list size="18">
+        <list size="17">
           <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" />
@@ -24,13 +23,12 @@
           <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="17">
+        <list size="16">
           <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" />
@@ -47,12 +45,11 @@
           <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_21" default="true" project-jdk-name="jbr-21" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" default="true" project-jdk-name="jbr-17" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
   <component name="ProjectType">

.idea/runConfigurations.xml

@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="RunConfigurationProducerService">
-    <option name="ignoredProducers">
-      <set>
-        <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>
-</project>

README.md

@@ -45,7 +45,7 @@ If using gradle kotlin  use line
 Add library to dependencies
 ```gradle
 dependencies {
-    implementation 'com.github.mik3y:usb-serial-for-android:3.9.0'
+    implementation 'com.github.mik3y:usb-serial-for-android:3.8.0'
 }
 ```
 
@@ -145,8 +145,8 @@ 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,
+*Note*: as of v3.5.0 this library detects CDC devices by USB interface types instead of fixed VID+PID,
-so custom probers are typically not required any more for CDC/ACM devices.
+so custom probers are typically not required any more for CDC 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
@@ -154,23 +154,22 @@ a compatible UsbDevice.
 
 ## Compatible Devices
 
-This library supports USB to serial converter chips with specific drivers
+This library supports USB to serial converter chips:
 * FTDI FT232R, FT232H, FT2232H, FT4232H, FT230X, FT231X, FT234XD
 * Prolific PL2303
 * Silabs CP2102, CP210*
-* Qinheng CH340, CH341A
+* Qinheng CH340, CH341A, CH9102
 
-some other device specific drivers
+devices implementing the CDC/ACM protocol like
-* 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
 * ...
 
+and some device specific drivers:
+* GsmModem devices, e.g. for Unisoc based Fibocom GSM modems
+* Chrome OS CCD (Closed Case Debugging)
+
 ## Help & Discussion
 
 For common problems, see the [FAQ](https://github.com/mik3y/usb-serial-for-android/wiki/FAQ) wiki page.

build.gradle

@@ -6,7 +6,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:8.9.1'
+        classpath 'com.android.tools.build:gradle:8.4.0'
     }
 }
 

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.6-all.zip

usbSerialExamples/build.gradle

@@ -3,7 +3,7 @@ plugins {
 }
 
 android {
-    compileSdkVersion 35
+    compileSdkVersion 34
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8
@@ -12,7 +12,7 @@ android {
 
     defaultConfig {
         minSdkVersion 17
-        targetSdkVersion 35
+        targetSdkVersion 34
         vectorDrawables.useSupportLibrary = true
 
         missingDimensionStrategy 'device', 'anyDevice'
@@ -28,6 +28,6 @@ android {
 
 dependencies {
     implementation project(':usbSerialForAndroid')
-    implementation 'androidx.appcompat:appcompat:1.6.1' // later versions have minsdk 21
+    implementation 'androidx.appcompat:appcompat:1.6.1'
-    implementation 'com.google.android.material:material:1.11.0' // later versions have minsdk 19
+    implementation 'com.google.android.material:material:1.11.0'
 }

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

@@ -214,7 +214,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
             status("connection failed: no driver for device");
             return;
         }
-        if(portNum >= driver.getPorts().size()) {
+        if(driver.getPorts().size() < portNum) {
             status("connection failed: not enough ports at device");
             return;
         }

usbSerialForAndroid/build.gradle

@@ -4,11 +4,11 @@ plugins {
 }
 
 android {
-    compileSdkVersion 35
+    compileSdkVersion 34
 
     defaultConfig {
         minSdkVersion 17
-        targetSdkVersion 35
+        targetSdkVersion 34
         consumerProguardFiles 'proguard-rules.pro'
         
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -31,13 +31,12 @@ android {
 }
 
 dependencies {
-    implementation "androidx.annotation:annotation:1.9.1"
+    implementation "androidx.annotation:annotation:1.8.0"
     testImplementation 'junit:junit:4.13.2'
-    testImplementation 'org.mockito:mockito-core:5.15.2'
+    testImplementation 'org.mockito:mockito-core:5.12.0'
-    androidTestImplementation 'androidx.appcompat:appcompat:1.6.1' // later versions have minsdk 21
+    androidTestImplementation 'androidx.test:core:1.5.0'
-    androidTestImplementation 'androidx.test:core:1.5.0' // later versions have minsdk 19
+    androidTestImplementation 'androidx.test:runner:1.5.2'
-    androidTestImplementation 'androidx.test:runner:1.5.2' // later versions have minsdk 19
+    androidTestImplementation 'commons-net:commons-net:3.10.0'
-    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'
 }
 

usbSerialForAndroid/coverage.gradle

@@ -8,7 +8,7 @@ android {
             // Used as fallback in usbSerialExample/build.gradle -> missingDimensionStrategy, but not for coverage report
             dimension 'device'
         }
-        mcp2221 {
+        arduino {
             dimension 'device'
             testInstrumentationRunnerArguments = ['test_device_driver': 'CdcAcm']
         }

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

@@ -645,13 +645,7 @@ public class DeviceTest {
             Thread.sleep(10);
             usb.write(new byte[]{(byte) 0xff});
             data = telnet.read(2);
-            if(usb.serialDriver instanceof CdcAcmSerialDriver) {
-                // not supported by MCP2221, other CDC devices might support it
-                assertThat("19000/7N1", data, equalTo(new byte[]{(byte) 0x00, (byte) 0xff}));
-                return;
-            } else {
             assertThat("19000/7N1", data, equalTo(new byte[]{(byte) 0x80, (byte) 0xff}));
-            }
         } catch (UnsupportedOperationException e) {
                 if(!usb.isCp21xxRestrictedPort)
                     throw e;
@@ -724,10 +718,6 @@ public class DeviceTest {
         usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_ODD);
         usb.write(_8n1);
         data = telnet.read(4);
-        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
-            // not supported by MCP2221, other CDC devices might support it
-            assertThat("19200/8N1", data, equalTo(_8n1));
-        } else {
         assertThat("19200/7O1", data, equalTo(_7o1));
 
         usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_EVEN);
@@ -735,6 +725,11 @@ public class DeviceTest {
         data = telnet.read(4);
         assertThat("19200/7E1", data, equalTo(_7e1));
 
+        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
+            // not supported by arduino_leonardo_bridge.ino, other devices might support it
+            usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_MARK);
+            usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_SPACE);
+        } else {
             usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_MARK);
             usb.write(_8n1);
             data = telnet.read(4);
@@ -763,6 +758,9 @@ public class DeviceTest {
         data = usb.read(4);
         assertThat("19200/7E1", data, equalTo(_7e1));
 
+        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
+            // not supported by arduino_leonardo_bridge.ino, other devices might support it
+        } else {
             telnet.setParameters(19200, 7, 1, UsbSerialPort.PARITY_MARK);
             telnet.write(_8n1);
             data = usb.read(4);
@@ -773,9 +771,6 @@ public class DeviceTest {
             data = usb.read(4);
             assertThat("19200/7S1", data, equalTo(_7s1));
 
-        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
-            ; // not supported by MCP2221, other CDC devices might support it
-        } else {
             usb.setParameters(19200, 7, 1, UsbSerialPort.PARITY_ODD);
             telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
             telnet.write(_8n1);
@@ -797,6 +792,10 @@ public class DeviceTest {
             }
         }
 
+        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
+            usb.setParameters(19200, 8, UsbSerialPort.STOPBITS_1_5, UsbSerialPort.PARITY_NONE);
+            // software based bridge in arduino_leonardo_bridge.ino is to slow for real test, other devices might support it
+        } else {
             // shift stopbits into next byte, by using different databits
             // a - start bit (0)
             // o - stop bit  (1)
@@ -810,10 +809,6 @@ public class DeviceTest {
             telnet.setParameters(19200, 6, 1, UsbSerialPort.PARITY_NONE);
             usb.write(new byte[]{(byte)0x41, (byte)0xf1});
             data = telnet.read(2);
-        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
-            // MCP2221 slightly slower, looks like 2 stop bits. could be different for other CDC devices
-            assertThat("19200/8N1", data, equalTo(new byte[]{1, 11}));
-        } else
             assertThat("19200/8N1", data, equalTo(new byte[]{1, 5}));
 
             // out 8N2:   addddddd dooaddddddddoo
@@ -837,6 +832,7 @@ public class DeviceTest {
             } catch(UnsupportedOperationException ignored) {
             }
         }
+    }
 
 
     @Test
@@ -887,6 +883,8 @@ public class DeviceTest {
         usb.setParameters(baudRate, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(baudRate, 8, 1, UsbSerialPort.PARITY_NONE);
         int purgeTimeout = 250;
+        if(usb.serialDriver instanceof CdcAcmSerialDriver)
+            purgeTimeout = 500;
         purgeWriteBuffer(purgeTimeout);
 
         // determine write buffer size
@@ -1057,17 +1055,18 @@ public class DeviceTest {
 
     @Test
     public void readBufferSize() throws Exception {
-        // looks like devices perform USB read with full mReadEndpoint.getMaxPacketSize() size (16, 32, 64, 512)
+        // looks like devices perform USB read with full mReadEndpoint.getMaxPacketSize() size (32, 64, 512)
         // if the buffer is smaller than the received result, it is silently lost
         //
         // for buffer > packet size, but not multiple of packet size, the same issue happens, but typically
         // only the last (partly filled) packet is lost.
+        if(usb.serialDriver instanceof CdcAcmSerialDriver)
+            return; // arduino sends each byte individually, so not testable here
         byte[] data;
         boolean purge = true;
 
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
-        int len = Math.min(16, usb.serialPort.getReadEndpoint().getMaxPacketSize()/2); // 8 for MCP2221, else 16
+        usb.ioManager.setReadBufferSize(8);
-        usb.ioManager.setReadBufferSize(len/2);
         usb.ioManager.start();
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
@@ -1076,15 +1075,13 @@ public class DeviceTest {
         telnet.write("1aaa".getBytes());
         data = usb.read(4);
         assertThat(data, equalTo("1aaa".getBytes()));
-
+        telnet.write(new byte[16]);
-        telnet.write(new byte[len]);
         try {
-            data = usb.read(len);
+            data = usb.read(16);
             if (usb.serialDriver instanceof Cp21xxSerialDriver && usb.serialDriver.getPorts().size() == 1)
                 assertNotEquals(0, data.length); // can be shorter or full length
-            else if (usb.serialDriver instanceof CdcAcmSerialDriver ||
+            else if (usb.serialDriver instanceof ProlificSerialDriver)
-                     usb.serialDriver instanceof ProlificSerialDriver)
+                assertTrue("expected > 0 and < 16 byte, got " + data.length, data.length > 0 && data.length < 16);
-                assertTrue("expected > 0 and < "+len+" byte, got " + data.length, data.length > 0 && data.length < len);
             else // ftdi, ch340, cp2105
                 assertEquals(0, data.length);
         } catch (IOException ignored) {
@@ -1124,13 +1121,12 @@ public class DeviceTest {
         telnet.write("2aaa".getBytes());
         data = usb.read(4, 8);
         assertThat(data, equalTo("2aaa".getBytes()));
-        telnet.write(new byte[len]);
+        telnet.write(new byte[16]);
-        data = usb.read(len, len/2);
+        data = usb.read(16, 8);
         if (usb.serialDriver instanceof Cp21xxSerialDriver && usb.serialDriver.getPorts().size() == 1)
             assertNotEquals(0, data.length); // can be shorter or full length
-        else if (usb.serialDriver instanceof CdcAcmSerialDriver ||
+        else if (usb.serialDriver instanceof ProlificSerialDriver)
-                 usb.serialDriver instanceof ProlificSerialDriver)
+            assertTrue("sporadic issue! expected > 0 and < 16 byte, got " + data.length, data.length > 0 && data.length < 16);
-            assertTrue("sporadic issue! expected > 0 and < "+len+" byte, got " + data.length, data.length > 0 && data.length < len);
         else // ftdi, ch340, cp2105
             assertEquals(0, data.length);
         telnet.write("2ccc".getBytes());
@@ -1150,6 +1146,8 @@ public class DeviceTest {
     @Test
     // provoke data loss, when data is not read fast enough
     public void readBufferOverflow() throws Exception {
+        if(usb.serialDriver instanceof CdcAcmSerialDriver)
+            telnet.writeDelay = 10; // arduino_leonardo_bridge.ino sends each byte in own USB packet, which is horribly slow
         usb.open();
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
@@ -1222,6 +1220,8 @@ public class DeviceTest {
         if(usb.serialDriver instanceof Ch34xSerialDriver)
             baudrate = 38400;
         int writeAhead = 5*baudrate/10; // write ahead for another 5 second read
+        if(usb.serialDriver instanceof CdcAcmSerialDriver)
+            writeAhead = 50;
 
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
         usb.ioManager.setReadTimeout(readTimeout);
@@ -1270,10 +1270,16 @@ public class DeviceTest {
 
     @Test
     public void writeSpeed() throws Exception {
-        // see logcat for performance results, speed is near physical limit at 11.5k
+        // see logcat for performance results
+        //
+        // CDC arduino_leonardo_bridge.ino has transfer speed ~ 100 byte/sec
+        // all other devices can get near physical limit:
+        // longlines=true:, speed is near physical limit at 11.5k
+        // longlines=false: speed is 3-4k for all devices, as more USB packets are required
         usb.open();
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
+        boolean longlines = !(usb.serialDriver instanceof CdcAcmSerialDriver);
 
         int linenr = 0;
         String line="";
@@ -1286,7 +1292,10 @@ public class DeviceTest {
         for(int seconds=1; seconds<=5; seconds++) {
             next += 1000;
             while (System.currentTimeMillis() < next) {
+                if(longlines)
                     line = String.format("%060d,", linenr++);
+                else
+                    line = String.format("%07d,", linenr++);
                 usb.write(line.getBytes());
                 expected.append(line);
                 data.append(new String(telnet.read(0)));
@@ -1416,16 +1425,19 @@ public class DeviceTest {
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
-        assertEquals(SerialInputOutputManager.State.STOPPED, usb.ioManager.getState());
         usb.ioManager.start();
         usb.waitForIoManagerStarted();
-        assertEquals(SerialInputOutputManager.State.RUNNING, usb.ioManager.getState());
+        assertTrue("iomanager thread", usb.hasIoManagerThread());
-        assertTrue("iomanager thread", usb.hasIoManagerThreads());
         try {
             usb.ioManager.start();
             fail("already running error expected");
         } catch (IllegalStateException ignored) {
         }
+        try {
+            usb.ioManager.run();
+            fail("already running error expected");
+        } catch (IllegalStateException ignored) {
+        }
         try {
             usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
             fail("setThreadPriority IllegalStateException expected");
@@ -1450,12 +1462,23 @@ public class DeviceTest {
         telnet.write(new byte[1]); // now uses 8 byte buffer
         usb.read(3);
 
-        // small writebuffer
+        // writebuffer resize
         try {
             usb.ioManager.writeAsync(new byte[8192]);
             fail("expected BufferOverflowException");
         } catch (BufferOverflowException ignored) {}
 
+        usb.ioManager.setWriteBufferSize(16);
+        usb.ioManager.writeAsync("1234567890AB".getBytes());
+        try {
+            usb.ioManager.setWriteBufferSize(8);
+            fail("expected BufferOverflowException");
+        } catch (BufferOverflowException ignored) {}
+        usb.ioManager.setWriteBufferSize(24); // pending date copied to new buffer
+        telnet.write("a".getBytes());
+        assertThat(usb.read(1), equalTo("a".getBytes()));
+        assertThat(telnet.read(12), equalTo("1234567890AB".getBytes()));
+
         // small readbuffer
         usb.ioManager.setReadBufferSize(8);
         Log.d(TAG, "setReadBufferSize(8)");
@@ -1467,42 +1490,74 @@ public class DeviceTest {
         telnet.write("d".getBytes());
         assertThat(usb.read(1), equalTo("d".getBytes()));
 
-        SerialInputOutputManager ioManager = usb.ioManager;
-        assertEquals(SerialInputOutputManager.State.RUNNING, usb.ioManager.getState());
         usb.close();
-        for (int i = 0; i < 100 && usb.hasIoManagerThreads(); i++) {
+        for (int i = 0; i < 100 && usb.hasIoManagerThread(); i++) {
             Thread.sleep(1);
         }
-        assertFalse("iomanager threads", usb.hasIoManagerThreads());
+        assertFalse("iomanager thread", usb.hasIoManagerThread());
-        assertNull(usb.ioManager);
-        assertEquals(SerialInputOutputManager.State.STOPPED, ioManager.getState());
-
-        usb.open();
-        ioManager = usb.ioManager;
-        assertEquals(SerialInputOutputManager.State.RUNNING, usb.ioManager.getState());
-        usb.serialPort.close(); // stop before ioManager
-        for (int i = 0; i < 100 && usb.hasIoManagerThreads(); i++) {
-            Thread.sleep(1);
-        }
-        assertFalse("iomanager threads", usb.hasIoManagerThreads());
-        assertEquals(SerialInputOutputManager.State.STOPPED, usb.ioManager.getState());
-
         SerialInputOutputManager.DEBUG = false;
+
+        // legacy start
+        usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START)); // creates new IoManager
+        usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
+        Executors.newSingleThreadExecutor().submit(usb.ioManager);
+        usb.waitForIoManagerStarted();
+        try {
+            usb.ioManager.start();
+            fail("already running error expected");
+        } catch (IllegalStateException ignored) {
+        }
     }
 
     @Test
     public void writeAsync() throws Exception {
         byte[] data, buf = new byte[]{1};
 
-        // write immediately, without waiting for read
+        // w/o timeout: write delayed until something is read
         usb.open();
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.writeAsync(buf);
         usb.ioManager.writeAsync(buf);
+        data = telnet.read(1);
+        assertEquals(0, data.length);
+        telnet.write(buf);
+        data = usb.read(1);
+        assertEquals(1, data.length);
+        data = telnet.read(2);
+        assertEquals(2, data.length);
+        usb.close();
+
+        // with timeout: write after timeout
+        usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
+        usb.ioManager.setReadTimeout(100);
+        usb.ioManager.start();
+        usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        usb.ioManager.writeAsync(buf);
+        usb.ioManager.writeAsync(buf);
         data = telnet.read(2);
         assertEquals(2, data.length);
-        usb.close();
+        usb.ioManager.setReadTimeout(200);
+
+        // with internal SerialTimeoutException
+        TestBuffer tbuf = new TestBuffer(usb.writeBufferSize + 2*usb.writePacketSize);
+        byte[] pbuf1 = new byte[tbuf.buf.length - 4];
+        byte[] pbuf2 = new byte[1];
+        System.arraycopy(tbuf.buf, 0,pbuf1, 0, pbuf1.length);
+        usb.ioManager.setWriteTimeout(20); // tbuf len >= 128, needs 133msec @ 9600 baud
+        usb.setParameters(9600, 8, 1, UsbSerialPort.PARITY_NONE);
+        telnet.setParameters(9600, 8, 1, UsbSerialPort.PARITY_NONE);
+        usb.ioManager.writeAsync(pbuf1);
+        for(int i = pbuf1.length; i < tbuf.buf.length; i++) {
+            Thread.sleep(20);
+            pbuf2[0] = tbuf.buf[i];
+            usb.ioManager.writeAsync(pbuf2);
+        }
+        while(!tbuf.testRead(telnet.read(-1)))
+            ;
     }
 
     @Test
@@ -1567,6 +1622,7 @@ public class DeviceTest {
         }
         Log.i(TAG, "average time per read " + (System.currentTimeMillis()-time)/i + " msec");
 
+        if(!(usb.serialDriver instanceof CdcAcmSerialDriver)) {
             int diffLen;
             usb.close();
             // no issue with high transfer rate and long read timeout
@@ -1594,6 +1650,7 @@ public class DeviceTest {
             //        got 00231,0000232,0000234,0000235,0000236,00
             //   expected 00231,0000232,0000233,0000234,0000235,00
         }
+    }
 
     @Test
     public void wrongDriver() throws Exception {
@@ -1797,6 +1854,11 @@ public class DeviceTest {
         assertThat(usb.getControlLine(usb.serialPort::getCD), equalTo(inputLineFalse));
         assertThat(usb.getControlLine(usb.serialPort::getRI), equalTo(usb.inputLinesOnlyRtsCts ? Boolean.FALSE : inputLineTrue));
         telnet.write(data);
+        if(usb.serialDriver instanceof CdcAcmSerialDriver)
+            // arduino: control line feedback as serial_state notification is not implemented.
+            // It does not send w/o RTS or DTR, so these control lines can be partly checked here.
+            assertEquals(0, usb.read().length);
+        else
             assertThat(Arrays.toString(data), usb.read(4), equalTo(data));
         usb.write(data);
         assertThat(Arrays.toString(data), telnet.read(4), equalTo(data));
@@ -1935,22 +1997,6 @@ public class DeviceTest {
         }
     }
 
-    @Test
-    public void flowControlBase() throws Exception {
-        usb.open();
-        usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
-        assertEquals(FlowControl.NONE, usb.serialPort.getFlowControl());
-        assertTrue(usb.serialPort.getSupportedFlowControl().contains(FlowControl.NONE));
-        for(FlowControl flowControl : FlowControl.values()) {
-            if(usb.serialPort.getSupportedFlowControl().contains(flowControl)) {
-                usb.serialPort.setFlowControl(flowControl);
-                assertEquals(flowControl, usb.serialPort.getFlowControl());
-            } else {
-                assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.setFlowControl(flowControl));
-            }
-        }
-    }
-
     @Test
     public void flowControlXonXoff() throws Exception {
         final byte[] off_on = new byte[]{'x',CommonUsbSerialPort.CHAR_XOFF,'y',CommonUsbSerialPort.CHAR_XON,'z'};
@@ -1960,11 +2006,12 @@ public class DeviceTest {
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_THREAD, UsbWrapper.OpenCloseFlags.NO_CONTROL_LINE_INIT));
         telnet.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
-        if(!usb.serialPort.getSupportedFlowControl().contains(FlowControl.XON_XOFF)) {
+        assertEquals(FlowControl.NONE, usb.serialPort.getFlowControl());
-            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.getXON());
-        }
         if (!usb.serialPort.getSupportedFlowControl().contains(FlowControl.XON_XOFF_INLINE) &&
                 !usb.serialPort.getSupportedFlowControl().contains(FlowControl.XON_XOFF)) {
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.setFlowControl(FlowControl.XON_XOFF_INLINE));
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.setFlowControl(FlowControl.XON_XOFF));
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.getXON());
             Assume.assumeTrue("flow control not supported", false);
         }
         if (usb.serialPort.getSupportedFlowControl().contains(FlowControl.XON_XOFF_INLINE) &&
@@ -1973,8 +2020,11 @@ public class DeviceTest {
         }
         if (usb.serialPort.getSupportedFlowControl().contains(FlowControl.XON_XOFF_INLINE)) {
             filter = new XonXoffFilter();
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.setFlowControl(FlowControl.XON_XOFF));
             usb.serialPort.setFlowControl(FlowControl.XON_XOFF_INLINE);
             assertEquals(FlowControl.XON_XOFF_INLINE, usb.serialPort.getFlowControl());
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.getXON());
+
             assertTrue(filter.getXON());
             assertThat(filter.filter(off_on), equalTo(off_on_filtered));
             assertTrue(filter.getXON());
@@ -1984,6 +2034,7 @@ public class DeviceTest {
             assertTrue(filter.getXON());
         } else {
             filter = null;
+            assertThrows(UnsupportedOperationException.class, () -> usb.serialPort.setFlowControl(FlowControl.XON_XOFF_INLINE));
             usb.serialPort.setFlowControl(FlowControl.XON_XOFF);
             assertEquals(FlowControl.XON_XOFF, usb.serialPort.getFlowControl());
             assertTrue(usb.serialPort.getXON());
@@ -2152,10 +2203,17 @@ public class DeviceTest {
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
 
         // early exit, if flow control not supported
-        if (!usb.serialPort.getSupportedFlowControl().contains(flowControl))
-            Assume.assumeTrue("flow control not supported", false);
         assertEquals(usb.inputLinesConnected ? EnumSet.of(ControlLine.RI) : EnumSet.noneOf(ControlLine.class), usb.serialPort.getControlLines()); // [1]
+        assertEquals(FlowControl.NONE, usb.serialPort.getFlowControl());
+        try {
             usb.serialPort.setFlowControl(flowControl);
+        } catch (UnsupportedOperationException ignored) {
+            if (usb.serialPort.getSupportedFlowControl().contains(flowControl)) {
+                assertTrue("flow control support expected", false);
+            } else {
+                Assume.assumeTrue("flow control not supported", false);
+            }
+        }
         assertEquals(flowControl, usb.serialPort.getFlowControl());
         if (!usb.inputLinesConnected)
             Assume.assumeTrue("flow control lines not connected", false);
@@ -2296,25 +2354,20 @@ public class DeviceTest {
     @Test
     public void setBreak() throws Exception {
         usb.open();
-        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
-            // not supported by MCP2221, other CDC devices might support it
-            try {
-                usb.serialPort.setBreak(true);
-                fail("setBreak error expected");
-            } catch (IOException ignored) {
-            }
-            return;
-        }
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         doReadWrite("");
+        usb.serialPort.setBreak(true);
         Thread.sleep(100);
         usb.serialPort.setBreak(false);
         // RFC2217 has SET_CONTROL + REQ_BREAK_STATE request, but this is not supported by pyserial
         // as there is no easy notification on <break> condition. By default break is returned as
         // 0 byte on Linux, see https://man7.org/linux/man-pages/man3/termios.3.html -> BRKINT
         byte[] data = telnet.read(1);
-        if(usb.isCp21xxRestrictedPort) {
+        if (usb.serialDriver instanceof CdcAcmSerialDriver) {
+            // BREAK forwarding not implemented by arduino_leonardo_bridge.ino
+            assertThat("<break>", data, equalTo(new byte[]{}));
+        } else if(usb.isCp21xxRestrictedPort) {
             assertThat("<break>", data, equalTo(new byte[]{0x55})); // send the last byte again?
         } else {
             assertThat("<break>", data, equalTo(new byte[]{0}));
@@ -2475,8 +2528,7 @@ public class DeviceTest {
         assertThrows(UnsupportedOperationException.class, wrongSerialPort::getControlLines);
         assertEquals(EnumSet.of(FlowControl.NONE), wrongSerialPort.getSupportedFlowControl());
         assertEquals(FlowControl.NONE, wrongSerialPort.getFlowControl());
-        wrongSerialPort.setFlowControl(FlowControl.NONE);
+        assertThrows(UnsupportedOperationException.class, () -> wrongSerialPort.setFlowControl(FlowControl.NONE));
-        assertThrows(UnsupportedOperationException.class, () -> wrongSerialPort.setFlowControl(FlowControl.RTS_CTS));
         assertThrows(UnsupportedOperationException.class, () -> wrongSerialPort.purgeHwBuffers(true, true));
         assertThrows(UnsupportedOperationException.class, () -> wrongSerialPort.setBreak(true));
     }

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

@@ -33,8 +33,6 @@ import java.util.concurrent.Callable;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
-import androidx.core.content.ContextCompat;
-
 public class UsbWrapper implements SerialInputOutputManager.Listener {
 
     public final static int     USB_READ_WAIT = 500;
@@ -94,7 +92,7 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
             intent.setPackage(context.getPackageName());
             PendingIntent permissionIntent = PendingIntent.getBroadcast(context, 0, intent, flags);
             IntentFilter filter = new IntentFilter("com.android.example.USB_PERMISSION");
-            ContextCompat.registerReceiver(context, usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED);
+            context.registerReceiver(usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED);
             usbManager.requestPermission(serialDriver.getDevice(), permissionIntent);
             for(int i=0; i<5000; i++) {
                 if(granted[0] != null) break;
@@ -152,7 +150,7 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
             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
+            writePacketSize = 64; writeBufferSize = 128;
         }
 
         readBufferSize = writeBufferSize;
@@ -258,15 +256,12 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
         throw new IOException("IoManager not started");
     }
 
-    public boolean hasIoManagerThreads() {
+    public boolean hasIoManagerThread() {
-        int c = 0;
         for (Thread thread : Thread.getAllStackTraces().keySet()) {
-            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_read"))
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName()))
-                c += 1;
+                return true;
-            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName() + "_write"))
-                c += 1;
         }
-        return c == 2;
+        return false;
     }
 
     // wait full time

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

@@ -10,13 +10,13 @@ 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.security.InvalidParameterException;
 import java.util.EnumSet;
 
 /**
@@ -29,7 +29,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     public static boolean DEBUG = false;
 
     private static final String TAG = CommonUsbSerialPort.class.getSimpleName();
-    private static final int MAX_READ_SIZE = 16 * 1024; // = old bulkTransfer limit prior to Android 9
+    private static final int MAX_READ_SIZE = 16 * 1024; // = old bulkTransfer limit
 
     protected final UsbDevice mDevice;
     protected final int mPortNumber;
@@ -208,7 +208,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
             //     /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
             long endTime = testConnection ? MonotonicClock.millis() + timeout : 0;
-            int readMax = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) ? length : Math.min(length, MAX_READ_SIZE);
+            int readMax = 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, ???
@@ -334,10 +334,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     public EnumSet<ControlLine> getSupportedControlLines() throws IOException { return EnumSet.noneOf(ControlLine.class); }
 
     @Override
-    public void setFlowControl(FlowControl flowcontrol) throws IOException {
+    public void setFlowControl(FlowControl flowcontrol) throws IOException { throw new UnsupportedOperationException(); }
-        if (flowcontrol != FlowControl.NONE)
-            throw new UnsupportedOperationException();
-    }
 
     @Override
     public FlowControl getFlowControl() { return mFlowControl; }

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

@@ -175,7 +175,7 @@ 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 not supported or values are not supported by a specific device
+     * @throws UnsupportedOperationException if values are not supported by a specific device
      */
     void setParameters(int baudRate, int dataBits, int stopBits, @Parity int parity) throws IOException;
 
@@ -257,7 +257,6 @@ 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
      */
     EnumSet<ControlLine> getControlLines() throws IOException;
 

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

@@ -9,23 +9,21 @@ package com.hoho.android.usbserial.util;
 import android.os.Process;
 import android.util.Log;
 
+import com.hoho.android.usbserial.driver.SerialTimeoutException;
 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 #runWrite()} ()} and {@link #runRead()} ()} ()} methods.
+ * Utility class which services a {@link UsbSerialPort} in its {@link #run()} method.
  *
  * @author mike wakerly (opensource@hoho.com)
  */
-public class SerialInputOutputManager {
+public class SerialInputOutputManager implements Runnable {
 
     public enum State {
         STOPPED,
-        STARTING,
         RUNNING,
         STOPPING
     }
@@ -35,6 +33,9 @@ public class SerialInputOutputManager {
     private static final String TAG = SerialInputOutputManager.class.getSimpleName();
     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;
 
@@ -45,8 +46,7 @@ public class SerialInputOutputManager {
     private ByteBuffer mWriteBuffer = ByteBuffer.allocate(BUFSIZ);
 
     private int mThreadPriority = Process.THREAD_PRIORITY_URGENT_AUDIO;
-    private final AtomicReference<State> mState = new AtomicReference<>(State.STOPPED);
+    private State mState = State.STOPPED; // Synchronized by 'this'
-    private CountDownLatch mStartuplatch = new CountDownLatch(2);
     private Listener mListener; // Synchronized by 'this'
     private final UsbSerialPort mSerialPort;
 
@@ -57,7 +57,7 @@ public class SerialInputOutputManager {
         void onNewData(byte[] data);
 
         /**
-         * Called when {@link SerialInputOutputManager#runRead()} ()} or {@link SerialInputOutputManager#runWrite()} ()} ()} aborts due to an error.
+         * Called when {@link SerialInputOutputManager#run()} aborts due to an error.
          */
         void onRunError(Exception e);
     }
@@ -87,9 +87,8 @@ public class SerialInputOutputManager {
      * @param threadPriority  see {@link Process#setThreadPriority(int)}
      * */
     public void setThreadPriority(int threadPriority) {
-        if (!mState.compareAndSet(State.STOPPED, State.STOPPED)) {
+        if (mState != State.STOPPED)
             throw new IllegalStateException("threadPriority only configurable before SerialInputOutputManager is started");
-        }
         mThreadPriority = threadPriority;
     }
 
@@ -98,7 +97,7 @@ public class SerialInputOutputManager {
      */
     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.get() != State.STOPPED)
+        if(mReadTimeout == 0 && timeout != 0 && mState != State.STOPPED)
             throw new IllegalStateException("readTimeout only configurable before SerialInputOutputManager is started");
         mReadTimeout = timeout;
     }
@@ -146,152 +145,83 @@ public class SerialInputOutputManager {
     }
 
     /**
-     * write data asynchronously
+     * when using writeAsync, it is recommended to use readTimeout != 0,
+     * else the write will be delayed until read data is available
      */
     public void writeAsync(byte[] data) {
         synchronized (mWriteBufferLock) {
             mWriteBuffer.put(data);
-            mWriteBufferLock.notifyAll(); // Notify waiting threads
         }
     }
 
     /**
-     * start SerialInputOutputManager in separate threads
+     * start SerialInputOutputManager in separate thread
      */
     public void start() {
-        if(mState.compareAndSet(State.STOPPED, State.STARTING)) {
+        if(mState != State.STOPPED)
-            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();
-            }
-        } else {
             throw new IllegalStateException("already started");
-        }
+        new Thread(this, this.getClass().getSimpleName()).start();
     }
 
     /**
-     * stop SerialInputOutputManager threads
+     * stop SerialInputOutputManager thread
      *
      * when using readTimeout == 0 (default), additionally use usbSerialPort.close() to
      * interrupt blocking read
      */
-    public void stop() {
+    public synchronized void stop() {
-        if(mState.compareAndSet(State.RUNNING, State.STOPPING)) {
+        if (getState() == State.RUNNING) {
-            synchronized (mWriteBufferLock) {
-                mWriteBufferLock.notifyAll(); // wake up write thread to check the stop condition
-            }
             Log.i(TAG, "Stop requested");
+            mState = State.STOPPING;
         }
     }
 
-    public State getState() {
+    public synchronized State getState() {
-        return mState.get();
+        return mState;
     }
 
     /**
-     * @return true if the thread is still running
+     * Continuously services the read and write buffers until {@link #stop()} is
+     * called, or until a driver exception is raised.
      */
-    private boolean isStillRunning() {
+    @Override
-        State state = mState.get();
+    public void run() {
-        return ((state == State.RUNNING) || (state == State.STARTING))
+        synchronized (this) {
-            && !Thread.currentThread().isInterrupted();
+            if (getState() != State.STOPPED) {
+                throw new IllegalStateException("Already running");
             }
-
+            mState = State.RUNNING;
-    /**
+        }
-     * Notify listener of an error
+        Log.i(TAG, "Running ...");
-     *
-     * @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));
+            if(mThreadPriority != Process.THREAD_PRIORITY_DEFAULT)
-            } catch (Throwable t) {
-                Log.w(TAG, "Exception in onRunError: " + t.getMessage(), t);
-            }
-        }
-    }
-
-    /**
-     * Set the thread priority
-     */
-    private void setThreadPriority() {
-        if (mThreadPriority != Process.THREAD_PRIORITY_DEFAULT) {
                 Process.setThreadPriority(mThreadPriority);
+            while (true) {
+                if (getState() != State.RUNNING) {
+                    Log.i(TAG, "Stopping mState=" + getState());
+                    break;
                 }
+                step();
             }
-
+        } catch (Exception e) {
-    /**
+            if(mSerialPort.isOpen()) {
-     * Continuously services the read buffers until {@link #stop()} is called, or until a driver exception is
+                Log.w(TAG, "Run ending due to exception: " + e.getMessage(), e);
-     * 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");
+                Log.i(TAG, "Socket closed");
+            }
+            final Listener listener = getListener();
+            if (listener != null) {
+              listener.onRunError(e);
             }
-            notifyErrorListener(e);
         } finally {
-            if (mState.compareAndSet(State.RUNNING, State.STOPPING)) {
+            synchronized (this) {
-                synchronized (mWriteBufferLock) {
+                mState = State.STOPPED;
-                    mWriteBufferLock.notifyAll(); // wake up write thread to check the stop condition
+                Log.i(TAG, "Stopped");
-                }
-            } else if (mState.compareAndSet(State.STOPPING, State.STOPPED)) {
-                Log.i(TAG, "runRead: Stopped mState=" + getState());
             }
         }
     }
 
-    /**
+    private void step() throws IOException {
-     * 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.
         byte[] buffer;
         synchronized (mReadBufferLock) {
@@ -309,28 +239,39 @@ public class SerialInputOutputManager {
                 listener.onNewData(data);
             }
         }
-    }
 
-    private void stepWrite() throws IOException, InterruptedException {
         // Handle outgoing data.
-        byte[] buffer = null;
+        buffer = null;
         synchronized (mWriteBufferLock) {
-            int len = mWriteBuffer.position();
+            len = mWriteBuffer.position();
             if (len > 0) {
                 buffer = new byte[len];
                 mWriteBuffer.rewind();
                 mWriteBuffer.get(buffer, 0, len);
                 mWriteBuffer.clear();
-                mWriteBufferLock.notifyAll(); // Notify writeAsync that there is space in the buffer
-            } else {
-                mWriteBufferLock.wait();
             }
         }
         if (buffer != null) {
             if (DEBUG) {
-                Log.d(TAG, "Writing data len=" + buffer.length);
+                Log.d(TAG, "Writing data len=" + len);
             }
+            try {
                 mSerialPort.write(buffer, mWriteTimeout);
+            } catch (SerialTimeoutException ex) {
+                synchronized (mWriteBufferLock) {
+                    byte[] buffer2 = null;
+                    int len2 = mWriteBuffer.position();
+                    if (len2 > 0) {
+                        buffer2 = new byte[len2];
+                        mWriteBuffer.rewind();
+                        mWriteBuffer.get(buffer2, 0, len2);
+                        mWriteBuffer.clear();
+                    }
+                    mWriteBuffer.put(buffer, ex.bytesTransferred, buffer.length - ex.bytesTransferred);
+                    if (buffer2 != null)
+                        mWriteBuffer.put(buffer2);
+                }
+            }
         }
     }
 

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

@@ -17,11 +17,6 @@ public class Log {
         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/com/hoho/android/usbserial/util/SerialInputOutputManagerTest.java

@@ -1,55 +0,0 @@
-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());
-    }
-}