HID Device. Best way to do event handling?
I'm using an HID device to connect to a CAN bus with several different types of sensors attached. Some of them respond quickly, others have more latency.
I'm using this USB HID Component for C# as a .dll in visual basic, which works great. http://www.codeproject.com/KB/cs/USB_HID.aspx
My current code for sending and receivin开发者_StackOverflow中文版g commands is somewhat troublesome. Sometimes commands and sent but not received fast enough. The problem can be with the sensor, not the actual vb code. We want the program to continue monitoring the other sensors, and not hang for too long.
Currently I'm using event handlers and loops, but I'm wondering if this might be better done by threading? or if my routine is the best for this situation.
Code Snippets:
CANUSB_Class.vb
Public Sub DataReceivedHandler(ByVal sender As Object, ByVal dataReceived As DataRecievedEventArgs)
For Each byteReceived As Byte In dataReceived.data
rxDataStruct.dataPacket(rxDataStruct.InPacketLength) = byteReceived
rxDataStruct.InPacketLength += 1
Next
rxDataReady = True
MainParsingRoutine.vb
sendCommand = False
CANPort.rxDataReady = False
Try
Do
Tries += 1
If Tries > 4 Then
Exit Do
End If
CANTimer.Start()
CANPort.transmitPacket(OutCANPacket)
'Wait for Return Packet
Do Until CANPort.rxDataReady = True Or _
CANTimer.ElapsedMilliseconds > timeout
System.Threading.Thread.Sleep(0)
Loop
If CANPORT.rxDataReady = True Then
sendCommand = True
Loop Until sendCommand = True
If anyone is developing a HID device and stumbles across this page I ended up using the ManualResetEvent.
In the CANUSB class the next line would be:
resetEvent.Set()
and then in the MainParsingRoutine.vb I changed:
Do Until CANPort.rxDataReady = True Or _
CANTimer.ElapsedMilliseconds > timeout
System.Threading.Thread.Sleep(0)
Loop
If CANPORT.rxDataReady = True Then
sendCommand = True
to:
CANUSB.resetEvent.WaitOne(100)
which times out after 100ms.
Works very well with our HID device, much better than our previous FTDI usb-serial device.
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