diff --git a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java
index a6414c9..3dc625d 100644
--- a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java
+++ b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/CommonUsbSerialPort.java
@@ -12,6 +12,8 @@ import android.hardware.usb.UsbEndpoint;
 import android.hardware.usb.UsbRequest;
 import android.util.Log;
 
+import com.hoho.android.usbserial.util.MonotonicClock;
+
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.EnumSet;
@@ -178,11 +180,11 @@ 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
-            long endTime = testConnection ? System.currentTimeMillis() + timeout : 0;
+            long endTime = testConnection ? MonotonicClock.millis() + timeout : 0;
             int readMax = Math.min(dest.length, MAX_READ_SIZE);
             nread = mConnection.bulkTransfer(mReadEndpoint, dest, readMax, timeout);
             // Android error propagation is improvable, nread == -1 can be: timeout, connection lost, buffer undersized, ...
-            if(nread == -1 && testConnection && System.currentTimeMillis() < endTime)
+            if(nread == -1 && testConnection && MonotonicClock.millis() < endTime)
                 testConnection();
 
         } else {
@@ -205,7 +207,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
     @Override
     public void write(final byte[] src, final int timeout) throws IOException {
         int offset = 0;
-        final long endTime = (timeout == 0) ? 0 : (System.currentTimeMillis() + timeout);
+        final long endTime = (timeout == 0) ? 0 : (MonotonicClock.millis() + timeout);
 
         if(mConnection == null) {
             throw new IOException("Connection closed");
@@ -229,7 +231,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
                 if (timeout == 0 || offset == 0) {
                     requestTimeout = timeout;
                 } else {
-                    requestTimeout = (int)(endTime - System.currentTimeMillis());
+                    requestTimeout = (int)(endTime - MonotonicClock.millis());
                     if(requestTimeout == 0)
                         requestTimeout = -1;
                 }
@@ -241,7 +243,7 @@ public abstract class CommonUsbSerialPort implements UsbSerialPort {
             }
             Log.d(TAG, "Wrote " + actualLength + "/" + requestLength + " offset " + offset + "/" + src.length + " timeout " + requestTimeout);
             if (actualLength <= 0) {
-                if (timeout != 0 && System.currentTimeMillis() >= endTime) {
+                if (timeout != 0 && MonotonicClock.millis() >= endTime) {
                     SerialTimeoutException ex = new SerialTimeoutException("Error writing " + requestLength + " bytes at offset " + offset + " of total " + src.length + ", rc=" + actualLength);
                     ex.bytesTransferred = offset;
                     throw ex;
diff --git a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java
index 40281c2..14f4ec9 100644
--- a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java
+++ b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/FtdiSerialDriver.java
@@ -12,6 +12,8 @@ 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;
@@ -146,11 +148,11 @@ public class FtdiSerialDriver implements UsbSerialDriver {
             }
             int nread;
             if (timeout != 0) {
-                long endTime = System.currentTimeMillis() + timeout;
+                long endTime = MonotonicClock.millis() + timeout;
                 do {
-                    nread = super.read(dest, Math.max(1, (int)(endTime - System.currentTimeMillis())), false);
-                } while (nread == READ_HEADER_LENGTH && System.currentTimeMillis() < endTime);
-                if(nread <= 0 && System.currentTimeMillis() < endTime)
+                    nread = super.read(dest, Math.max(1, (int)(endTime - MonotonicClock.millis())), false);
+                } while (nread == READ_HEADER_LENGTH && MonotonicClock.millis() < endTime);
+                if(nread <= 0 && MonotonicClock.millis() < endTime)
                     testConnection();
             } else {
                 do {
diff --git a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java
index 2be6f61..60aab27 100644
--- a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java
+++ b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/driver/ProlificSerialDriver.java
@@ -17,6 +17,7 @@ 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.util.Collections;
@@ -174,9 +175,9 @@ public class ProlificSerialDriver implements UsbSerialDriver {
             try {
                 while (!mStopReadStatusThread) {
                     byte[] buffer = new byte[STATUS_BUFFER_SIZE];
-                    long endTime = System.currentTimeMillis() + 500;
+                    long endTime = MonotonicClock.millis() + 500;
                     int readBytesCount = mConnection.bulkTransfer(mInterruptEndpoint, buffer, STATUS_BUFFER_SIZE, 500);
-                    if(readBytesCount == -1 && System.currentTimeMillis() < endTime)
+                    if(readBytesCount == -1 && MonotonicClock.millis() < endTime)
                         testConnection();
                     if (readBytesCount > 0) {
                         if (readBytesCount != STATUS_BUFFER_SIZE) {
diff --git a/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/MonotonicClock.java b/usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/MonotonicClock.java
new file mode 100644
index 0000000..befc3dc
--- /dev/null
+++ b/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;
+    }
+
+}