I’m trying to set the communication with an arduino nano.

I’m exploring the use of overlapped I/O, this is just a test and I am aware that I have no interest in using overlapped I/O in this state.

I’m using an arduino nano that sends a character (“p”) every seconds with the Serial.print.

I’m calling the WaitCommEvent in a loop.
My issue is, if I remove the call to the Sleep before the WaitCommEvent, the character sent by the arduino isn’t displayed anymore.

Here is an abstract of how my code works :

• Open the comm port by calling CreateFile with the FILE_FLAG_OVERLAPPED flag.
• Call the setCommMask, setCommTimeout
• Create the appropriate event in the Overlapped structure
• Call WaitCommEvent with the overlapped structure.
• Then WaitForSingleObject on the event.
• ReadFile when the event is signaled.

    while (1) {
          Status = SetCommMask(hComm, EV_RXCHAR); //  | EV_CTS | EV_DSR | EV_TXEMPTY | EV_ERR | EV_RLSD
        if (Status == FALSE)
        {
            printf_s("nError to in Setting CommMasknn");
            CloseHandle(hComm);
        }
        //Setting WaitComm() Event
        dwEventMask = NULL;
        char  ReadData[100] = { 0 };        //temporary Character

        Sleep(500);
        Status = WaitCommEvent(hComm, &dwEventMask, &o); //Wait for the character to be received
        if (GetLastError() != ERROR_IO_PENDING) {
            printf("IO_NOT_PENDING %dn", GetLastError());
        }
        DWORD lpModemStat;
        dwRes = WaitForSingleObject(o.hEvent, INFINITE);
        switch (dwRes) {
        case WAIT_OBJECT_0:
            if (!GetOverlappedResult(hComm, &o, &dwRead, FALSE)) {
                DWORD err = GetLastError();
                printf("OVERLAPPED ERROR %dn", err);
            }
            printf("n read %dn", dwRead);

            if (dwEventMask & EV_RXCHAR) {
                Status = ReadFile(hComm, &ReadData, sizeof(ReadData), &NoBytesRead, &o);
                ResetEvent(o.hEvent);
                for (int i = 0; i < 100; i++) {
                    std::cout << ReadData[i];
                }
            }
            break;
        case WAIT_TIMEOUT:
            break;
        default:
            break;
        }
    }

I put the setCommMask in the loop because if I don’t, I get an error on the WaitCommeEvent that returns the code 87 – The parameter is incorrect.

I think there is something wrong with the way I use the functions or in my understanding.