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"Blue Screen Of Death" Hardware or Software?

Hope I don't get to verbose, but I want to be clear:
I'm writing an app in VB.Net, and declaring/using separate threads that monitor a serial port for both input or output. It works fine - until I get the "Blue Screen Of Death" with the message  "IRQ_NOT_LESS_OR_EQUAL". Of course, I suspected a thread problem - so I took the code for the thread (a simple loop) and wrote it into a standalone test app. After a while, the test app crashes also (with no separate threads).

The thread code is a simple 'Do" loop. It calls MySerialPort.Receive, which is synchronous, so it wait's till it gets a character. It appends the character to a string in a buffer array. When a <cr> is read in, the completed string is used as a parameter in an Event call (I have rem'd out the RaiseEvent in the test code, just to make sure that it wasn't part of the problem.) The code can run non-stop for 10-60 minutes, then the BSOD occurs.

The HeartBeatTimerFlag get's set with every line that is read in. There is a 500 mS timer that will trigger a start signal to the equipment this is controlling if no lines appear for .5 seconds.

Also, the serial port isn't a regular com port - it's a Keyspan USB serial port at COM3, no handshaking, 115200 baud.

I have attached the entire loop for you to see - can someone tell me why the BSOD is occuring? THANKS!!


Private Sub GetData()
        Do
            Application.DoEvents()
            If MySerialPort.BytesToRead <> 0 Then
                Dim returnData As String = Chr(MySerialPort.ReadByte)  
                B = InStr(returnData, vbCr)
                If B <> 0 Then
                    'got a cr, line is done
                    ReceiveApplicationQueue(ReceiveApplicationQueuePointer) = ReceiveApplicationQueue(ReceiveApplicationQueuePointer) & Strings.Left(returnData, B)
                    HeartBeatTimerFlag = True
                    Debug.WriteLine(ReceiveApplicationQueue(ReceiveApplicationQueuePointer))
                    'RaiseEvent GotApplicationString(ReceiveApplicationQueue(ReceiveApplicationQueuePointer))
                    ReceiveApplicationQueue(ReceiveApplicationQueuePointer) = ""
                    ReceiveApplicationQueuePointer = (ReceiveApplicationQueuePointer + 1) Mod 500
                    ReceiveApplicationQueue(ReceiveApplicationQueuePointer) = Strings.Right(returnData, Len(returnData) - B)
                    returnData = ""
                Else
                    ReceiveApplicationQueue(ReceiveApplicationQueuePointer) = ReceiveApplicationQueue(ReceiveApplicationQueuePointer) & returnData
                End If
            End If
        Loop
 
    End Sub

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LongDave
Asked:
LongDave
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1 Solution
 
LongDaveAuthor Commented:
I forgot to add that the "Application.DoEvents" was not in this loop in the threaded version. I just added it into the standalone so that I wouldn't lock up anything. Incidentally, this is using VB.NET in VS 2005. Thanks!
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Priest04Commented:
Well, the error can be both hardware and software, so its hard to say it. Could be the driver is not good. What you could do to eliminate hardware is to try it on different PC. If no BSOD, then its a software problem.

Maybe you should try setting a lower speed, like 9600, for testing purposes.
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LongDaveAuthor Commented:
It wasn't the software - apparently the old driver for the USB-Serial converter did not work too well with XP-SP3. When the software is plugged into a computer with a 'real' com port, it worked fine.
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