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windowsserial-portwindev

Getting DTR and RTS pin of serial port in C on Windows platform

How to get DTR and RTS status of serial port on a windows platform? I want to read the current state (ON or OFF) of these two pins.

I can set pins with :

EscapeCommFunction(hSerial,SETRTS);

But I don't know how to read the pin status.

Since on Linux, it can be done with the following code, I assume it is technicaly feasable:

int status=0;
ioctl(fd, TIOCMGET, &status);
return status & TIOCM_RTS;
Solution

  • Using inc\api\ntddser.h API and winioctl.h, you can access DTR and RTS status. Call DeviceIoControl, set the second parameter to IOCTL_SERIAL_GET_DTRRTS:

    Call: 

    DeviceIoControl(
    handle, // handle returned by CreateFile
    IOCTL_SERIAL_GET_DTRRTS,
    NULL,
    0,
    &Status, // pointer to a DWORD variable 1
    sizeof(Status),
    &unused, // pointer to a DWORD variable
    pOverlapped // optional pointer to overlapped buffer (may be NULL)
);

    Documentation about DeviceIoControl here.