Re: serial communications

<mike7411@gmail.com> wrote in message
news:1161108650.843778.120740@m7g2000cwm.googlegroups.com...


That depends what your needs are. The prevailing wisdom would have you go to
www.codeproject.com and download a class library.

The _quick hack_ below demonstrates the asynchronous transmission of the
Hayes command "identify" to a modem on COM3: and the reception of the
response. In the process, it sets the baud rate to 9600 and (almost
nonsensical) timeout values.

Regards,
Will

#include <windows.h>
#include <stdio.h>

int main(int argc, char **argv)
{
 char szBuffer[80];
 DCB dcb = {0};
 DWORD dwRead, dwWritten;
 HANDLE hComm;
 OVERLAPPED ovlr = {0}, ovlw = {0};
 COMMTIMEOUTS cto;

 // Create events for overlapped operation

 ovlr.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 ovlw.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

 // Open the port

 hComm = CreateFile("\\\\.\\COM3", GENERIC_READ | GENERIC_WRITE,
            0, NULL, OPEN_EXISTING,
                 FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);

 // Get the state of the device and modify it

 dcb.DCBlength = sizeof(dcb);
 GetCommState(hComm, &dcb);
 dcb.BaudRate = CBR_9600;
 SetCommState(hComm, &dcb);

 // Set the timeout parameters

 cto.ReadIntervalTimeout = 1000;
 cto.ReadTotalTimeoutConstant = 1000;
 cto.ReadTotalTimeoutMultiplier = 1000;
 cto.WriteTotalTimeoutConstant = 1000;
 cto.WriteTotalTimeoutMultiplier = 1000;

 SetCommTimeouts(hComm, &cto);

 // Send a command and receieve a response. Note that
 // we post the receive in advance of sending the
 // command in order not to miss anything

 printf("\r\nSending: ATI1\r\n");

 ReadFile (hComm, szBuffer, sizeof(szBuffer), &dwRead, &ovlr);
 WriteFile(hComm, "ATI1\r", strlen("ATI1\r"), &dwWritten, &ovlw);

 // Wait for the receive to complete and display the response

 if ( GetOverlappedResult(hComm, &ovlr, &dwRead, TRUE) )
 {
  szBuffer[dwRead] = 0;
  printf("Received: %s\r\n", szBuffer);
 }

 // Close the device

 CloseHandle(hComm);

 return 0;
}