C# problem with two threads and hardware access
- by mack369
I'm creating an application which communicates with the device via FT2232H USB/RS232 converter. For communication I'm using FTD2XX_NET.dll library from FTDI website.
I'm using two threads:
first thread continuously reads data from the device
the second thread is the main thread of the Windows Form Application
I've got a problem when I'm trying to write any data to the device while the receiver's thread is running. The main thread simply hangs up on ftdiDevice.Write function.
I tried to synchronize both threads so that only one thread can use Read/Write function at the same time, but it didn't help.
Below code responsible for the communication. Note that following functions are methods of FtdiPort class.
Receiver's thread
private void receiverLoop()
{
if (this.DataReceivedHandler == null)
{
throw new BackendException("dataReceived delegate is not set");
}
FTDI.FT_STATUS ftStatus = FTDI.FT_STATUS.FT_OK;
byte[] readBytes = new byte[this.ReadBufferSize];
while (true)
{
lock (FtdiPort.threadLocker)
{
UInt32 numBytesRead = 0;
ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);
if (ftStatus == FTDI.FT_STATUS.FT_OK)
{
this.DataReceivedHandler(readBytes, numBytesRead);
}
else
{
Trace.WriteLine(String.Format("Couldn't read data from ftdi: status {0}", ftStatus));
Thread.Sleep(10);
}
}
Thread.Sleep(this.RXThreadDelay);
}
}
Write function called from main thread
public void Write(byte[] data, int length)
{
if (this.IsOpened)
{
uint i = 0;
lock (FtdiPort.threadLocker)
{
this.ftdiDevice.Write(data, length, ref i);
}
Thread.Sleep(1);
if (i != (int)length)
{
throw new BackendException("Couldnt send all data");
}
}
else
{
throw new BackendException("Port is closed");
}
}
Object used to synchronize two threads
static Object threadLocker = new Object();
Method that starts the receiver's thread
private void startReceiver()
{
if (this.DataReceivedHandler == null)
{
return;
}
if (this.IsOpened == false)
{
throw new BackendException("Trying to start listening for raw data while disconnected");
}
this.receiverThread = new Thread(this.receiverLoop);
//this.receiverThread.Name = "protocolListener";
this.receiverThread.IsBackground = true;
this.receiverThread.Start();
}
The ftdiDevice.Write function doesn't hang up if I comment following line:
ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);
