Bugfix in STM32SerialDriver: Read bytes are not returned (wrap does …

UsbSerialForAndroid/driver/CdcAcmSerialDriver.cs

@@ -68,7 +68,7 @@ class CdcAcmSerialPort : CommonUsbSerialPort
             private static int SET_CONTROL_LINE_STATE = 0x22;
             private static int SEND_BREAK = 0x23;
 
-            private IUsbSerialDriver Driver;
+            private new readonly IUsbSerialDriver Driver;
 
             //public CdcAcmSerialPort(UsbDevice device, int portNumber) : base(device, portNumber)
             //{

UsbSerialForAndroid/driver/Ch34xSerialDriver.cs

@@ -59,7 +59,7 @@ public class Ch340SerialPort : CommonUsbSerialPort
             private UsbEndpoint mReadEndpoint;
             private UsbEndpoint mWriteEndpoint;
 
-            private IUsbSerialDriver Driver;
+            private new readonly IUsbSerialDriver Driver;
             private string TAG => (Driver as Ch34xSerialDriver)?.TAG;
 
             public Ch340SerialPort(UsbDevice device, int portNumber, IUsbSerialDriver driver) : base(device, portNumber)

UsbSerialForAndroid/driver/Cp21xxSerialDriver.cs

@@ -86,7 +86,7 @@ public class Cp21xxSerialPort : CommonUsbSerialPort
             private UsbEndpoint mReadEndpoint;
             private UsbEndpoint mWriteEndpoint;
 
-            private new IUsbSerialDriver Driver;
+            private readonly new IUsbSerialDriver Driver;
             private string TAG => (Driver as Cp21xxSerialDriver)?.TAG;
 
 

UsbSerialForAndroid/driver/FtdiSerialDriver.cs

@@ -103,7 +103,7 @@ private class FtdiSerialPort : CommonUsbSerialPort
             private Boolean rts = false;
             private int breakConfig = 0;
 
-            private IUsbSerialDriver Driver;
+            private new readonly IUsbSerialDriver Driver;
 
 
             private String TAG = typeof (FtdiSerialDriver).Name;

UsbSerialForAndroid/driver/ProlificSerialDriver.cs

@@ -132,7 +132,8 @@ protected enum DeviceType { DEVICE_TYPE_01, DEVICE_TYPE_T, DEVICE_TYPE_HX, DEVIC
             Boolean mStopReadStatusThread = false;
             private IOException mReadStatusException = null;
 
-            private IUsbSerialDriver Driver;
+            private new readonly IUsbSerialDriver Driver;
+
 
             private string TAG => (Driver as ProlificSerialDriver)?.TAG;
 

UsbSerialForAndroid/driver/STM32SerialDriver.cs

@@ -56,7 +56,7 @@ public class STM32SerialPort : CommonUsbSerialPort
 			bool mRts = false;
 			bool mDtr = false;
 
-			IUsbSerialDriver Driver;
+			private new readonly IUsbSerialDriver Driver;
 
 			const int USB_WRITE_TIMEOUT_MILLIS = 5000;
 
@@ -141,8 +141,15 @@ public override int Read(byte[] dest, int timeoutMillis)
 					try
 					{
 						request.Initialize(mConnection, mReadEndpoint);
-						ByteBuffer buf = ByteBuffer.Wrap(dest);
-						if (!request.Queue(buf, dest.Length))
+
+                        // wrap not work here
+                        // byte[] is a primitive C# value type and not a Java.Lang.Object reference type
+                        // when you do ByteBuffer.Wrap (dest), Java has no reference to the actual C# byte[], Java will instead make a copy of the bytes.
+                        // ByteBuffer buf = ByteBuffer.Wrap(dest);
+
+                        ByteBuffer buf = ByteBuffer.AllocateDirect(dest.Length);
+
+                        if (!request.Queue(buf, buf.Limit()))
 							throw new IOException("Error queuing request");
 
 						UsbRequest response = mConnection.RequestWait();
@@ -151,7 +158,13 @@ public override int Read(byte[] dest, int timeoutMillis)
 
 						int nread = buf.Position();
 						if (nread > 0)
-							return nread;
+						{
+                            // set back buffer position to 0
+							buf.Rewind();
+							// copy the bytes back
+                            buf.Get(dest, 0, nread);
+                            return nread;
+						}
 
 						return 0;
 					}
@@ -166,7 +179,7 @@ public override int Read(byte[] dest, int timeoutMillis)
 				{
 					int readAmt = Math.Min(dest.Length, mReadBuffer.Length);
 					numBytesRead = mConnection.BulkTransfer(mReadEndpoint, mReadBuffer, readAmt, timeoutMillis);
-					if(numBytesRead < 0)
+					if(numBytesRead <= 0)
 					{
 						// This sucks: we get -1 on timeout, not 0 as preferred.
 						// We *should* use UsbRequest, except it has a bug/api oversight