There is nothing plugged on com1....???
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Thread: There is nothing plugged on com1....???

  1. #1
    Join Date
    Apr 2004
    Posts
    15

    There is nothing plugged on com1....???

    Hi,
    I have to check if in the port Com1 is puggled some device.
    I had use this code and if the device is plugged it is work correctly but if there is nothing it don' t return nothing
    Some advice???


    ....
    hCom = CreateFile( port,
    GENERIC_READ | GENERIC_WRITE,
    0, // comm devices must be opened w/exclusive-access
    NULL, // no security attributes
    OPEN_EXISTING, // comm devices must use OPEN_EXISTING
    0, // not overlapped I/O
    NULL // hTemplate must be NULL for comm devices
    );

    if (hCom == INVALID_HANDLE_VALUE) {
    dwError = GetLastError();
    return E_OPENING;
    }
    ...

  2. #2
    Join Date
    May 2000
    Location
    NJ
    Posts
    640
    If the device when connected to the Com1 port brings up Carrier (DCD), then you can check for it.

    // Code example


    BOOL CheckCarrier()
    {
    DWORD dwModemStatus = 0;
    BOOL fDeviceCarrier = FALSE;
    dwModemStatus = EV_RLSD;

    // No DCD from Device
    if((m_hComm==NULL) || (m_hComm==INVALID_HANDLE_VALUE))
    {
    return FALSE;
    }

    if(!GetCommModemStatus(m_hComm, &dwModemStatus))
    {
    // DCD still low;
    }
    else
    {
    // DCD is high from device
    fDeviceCarrier = MS_RLSD_ON & dwModemStatus;
    return fDeviceCarrier;
    }
    return FALSE;
    }

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