CODEWITHSUNDEEP
c#callbacksynchronous
chwi
chwi

Reputation: 2802

Listen to synchronous callbacks with C#

I have a program which write data to a USB HID device. When data is received from the USB device I get a callback from the usblib library through a delegate event DataRecievedEventHandler.

I am used to programming on firmware with interrupts, so that I can do 

while(!flag); // Will continue when interrupt triggers and change the flag

I want to write an array element by element to the USB and wait for a return from the device after each array element

for (int i = 0; i > 16; i++)
{ 
    sendUsbData(array[i]);
    while(!receivedComplete);
    // Wait for response from USB before transmitting next iteration
}

The problem is that the callback will not get triggered when I'm spooling in that while loop. Any suggestion on how to do these kind of operations?

The library I am using for USB communication is the same as this one. In SpecifiedDevice.cs there is a method called public void SendData(byte[] data) which I am using to send arrays of bytes.

Transmit method:

public void sendUsbData(byte _txData)
{
    byte[] txData = new byte[this.usb.SpecifiedDevice.OutputReportLength];
    txData[1] = 0x50; // 0x50 = loopback command. Element 0 is always 0x00

    int pos = 2;
    foreach (byte b in _flashData)
    {
        txData[pos] = b;
        pos++;
    }

        this.usb.SpecifiedDevice.SendData(txData);
}

Upon received data from USB, the callback usb_OnDataRecieved is called. 

private void usb_OnDataRecieved(object sender, DataRecievedEventArgs args)
{
    this.ParseReceivePacket(args.data); // Format to string and print to textbox
    /*public bool*/receiveComplete = true; 
}

Upvotes: 0

Views: 333

Answers (1)

meilke
meilke

Reputation: 3280

You could switch to using a AutoResetEvent wait handle:

public void sendUsbData(byte _txData)
{
  byte[] txData = new byte[this.usb.SpecifiedDevice.OutputReportLength];
  txData[1] = 0x50; // 0x50 = loopback command. Element 0 is always 0x00

  int pos = 2;
  foreach (byte b in _flashData)
  {
    txData[pos] = b;
    pos++;
  }

  // reset member wait handle
  waitHandle = new AutoResetEvent(false); 
  this.usb.SpecifiedDevice.SendData(txData);
}

private void usb_OnDataRecieved(object sender, DataRecievedEventArgs args)
{
  this.ParseReceivePacket(args.data); // Format to string and print to textbox

  // signal member wait handle
  waitHandle.Set();
}

And then in your for loop:

for (int i = 0; i > 16; i++)
{ 
  sendUsbData(array[i]);

  // wait for member wait handle to be set
  waitHandle.WaitOne();
}

Upvotes: 1

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