InstallComCallback and EV_EVENT2
Hi,
I have a problem with InstallComCallback and special events generated by the port driver.
I'm controlling a FTDI-based device by using a virtual com port driver and the RS-232 library functions from CVI. I want to use a com-callback for a special event (EV_EVENT2) which is generated by the driver on surprise removal of the device. But InstallComCallback() doesn't accept it and returns 'invalid argument'.
So I tried to call GetSystemComHandle() and use the Windows API function WaitCommEvent(). But the documentation of WaitCommEvent() told me, that WaitCommEvent() does not return until the specified event occurs if the com port wasn't opened with FILE_FLAG_OVERLAPPED. But it seems to be opened without this flag by OpenComConfig(), so WaitCommEvent() doesn't return and my whole application stopped.
Are there any suggestions how I can handle this event without replacing all RS-232 library functions with the Windows API calls?
Best regards,
Martin Schmidt
Hi Martin
I found several informations about using the ComCallback:
Using the RS232 Library InstallComCallback Function to Handle Events
Options for Using the LabWindows/CVI ComCallback with Serial Interfaces
Otherway, to catch events that occur when you remove a serial device requires that
you use Windows-based functionality to catch Windows events.
How Do CVI Panels Process Windows Messages?
Hope that helps.
Kind regards
Pixar
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Hope someone could help with this issue. I have simple application which process ASCII data coma separated from serial port at speed of 115.2kbps. There is 6 columns of unsigned short data . I set-up COM call back function to receive data and I created separate thread function to plot data on a 6 graphs - PlotWaveform() used. Plots roll-over from beginning every time it receives more then 3000 samples. There is couple of more command buttons to set-up serial port, save data to a file, and exit application.
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Go to Solution.Thanks Roberto,
a) I continiously receive RS232 data from external device without request. I install COM callback func.
InstallComCallback (comport, eventMask, notifyCount,eventChar, ComCallback, NULL); where is:
static int eventChar =13;
static int notifyCount =115;
Call back functions where I process data and store them into 6 arrays of 3000 elements:
void CVICALLBACK ComCallback(int portNo, int eventMask,void *datax);
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static int CVICALLBACK PlotingThreadFunc (void *functionData)
while(1)
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0.0, 1.0, VAL_FAT_LINE, VAL_EMPTY_SQUARE, VAL_SOLID, 1,
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PlotWaveform (panelHandle, PANEL_GRAPH_CAP6,
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VAL_UNSIGNED_SHORT_INTEGER, 1.0, 0.0, 0.0, 1.0,
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The plotFLAG is set in the ComCallback() when data is received.
d) I plot as above, whoole data arrays when data is received.
e) “Plots Roll-Over” I meant: Plots are window into data steram and when it is plotted max. number of elements (3000) then arrays are erased and start new data plot from beginning. -
I seem to have found a slight issue using InstallComCallback() between WinXP and Win7 target machines.
I developed my initial software on WinXP. The following two bits of code worked fine in WinXP with an eventMask = LWRS_RXFLAG | LWRS_RECEIVE. But when I distributed the final software to Win7 machines, I was observing the callback getting called twice each time.
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// Callback scanner COM function
void BarcodeScanner(int scannerPortNumber, int eventMask, void *callbackdata)
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// raise the data flag
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FlushInQ(scannerPortNumber);
And here's my use of InstallComCallback():
void InitScannerComm(void)
int notifyCount = SCANNER_MIN_BYTES;
int eventChar = SCANNER_EOS; // terminator charactor
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int dataBits = SCANNER_DATABITS;
int stopBits = SCANNER_STOPBITS;
int inputQueueSize = SCANNER_MAX_BYTES;
int parity = SCANNER_PARITY;
int comportRing = 0;
int i;
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FlushInQ(scannerPortNumber);
FlushOutQ(scannerPortNumber);
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GetNumListItems(tabPage2Handle,TABPANEL2_COMPORT,&comportRing);
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else
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A bit of background... the device sending COM traffic is a barcode scanner from Motorola/Symbol. I have it set up in a virtual COM mode. Using RealTerm in hex display mode, I can confirm that this hardware is set up correctly, i.e., it is sending what it should be (a string in the form: "012345" with a CR at the end).
And I know that the string is correct in that the callback gets called. The puzzling thing is that in Win7 only, the callback gets called twice and then it's done. The second time through, the string is all nulls.
My fix was to eliminate the LWRS_RECEIVE option in the eventMask (i.e., remove the notifyCount threshold). Phew!
Is this a bug?
Solved!
Go to Solution.At this point it is hard to tell. We have seen some issues in COM port behavior when comparing between XP and 7. In order for us to verify that it is a bug, we would need to be able to reproduce this on our end. If you could think of a way for us to reproduce this behavior without your hardware (the scanner) then we'd be glad to test this out and file a corrective action request to R&D to look into. We do appreciate your time to post to or forums and making a note of this as this may happen to fellow developers and at least they can look at your workaround for a working solution.
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