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Ken, N9VV reported an error in PowerSDR 1.3.13 where opening a serial port after it had already been opened and then closed would cause an exception. The serial port will remain unavailable until PowerSDR is exited and then restarted.

Using PortMon, I immediately saw the error: I was trying to close the handle to the com port without first cancelling a WaitCommEvent(). The file handle to the com port would only be closed when PowerSDR exited.

The correction to the source code was pretty easy:

In SerialStream.cs line 1383, function FreeHandle needs to be changed to:




protected internal override void FreeHandle(IntPtr handle)
{
    if (_ownsHandle)
    {
        //Important! Must cancel all events before closing file!!!
        Win32API_Serial.SetCommMask(handle, 0);
        //Now we can close the file handle
        Win32API_Serial.CloseHandle(handle);
    }
}


Calling SetCommMask() with a mask of 0 cancells the current WaitCommEvent() allowing the com port to be closed and correcting the problem.

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Anonymous said…
Nice blog. :) Thanks for the link. I'll add it to my favorites so I can check up on it every once in a while.
2:39 PM
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