// simple232.cpp : Defines the entry point for the console application
#include "windows.h"
#include "stdio.h"
#include "conio.h"

int main(int argc, char* argv[])
{
   HANDLE hCom = CreateFile("COM1", GENERIC_READ | GENERIC_WRITE, 0,
                            NULL, OPEN_EXISTING, 0, NULL);
   SetupComm(hCom, 128, 128);

   DCB dcb;
   GetCommState(hCom, &dcb); dcb.BaudRate    =CBR_9600;  dcb.ByteSize =8;
                             dcb.Parity      =NOPARITY;  dcb.StopBits =ONESTOPBIT;
                             dcb.fAbortOnError = FALSE;
   SetCommState(hCom, &dcb);

   COMMTIMEOUTS timeouts;
   GetCommTimeouts (hCom, &timeouts);
            timeouts.ReadIntervalTimeout       =50;
            timeouts.ReadTotalTimeoutConstant  =50;  timeouts.ReadTotalTimeoutMultiplier  =10;
            timeouts.WriteTotalTimeoutConstant =50;  timeouts.WriteTotalTimeoutMultiplier =10;
   SetCommTimeouts (hCom, &timeouts);

   char rBuff[128]; int rLen=1, rPos =0; //only first byte used in example
   char sBuff[] ="3A 30 31 30 33 30 30 30 30 30 30 30 34 46 38 0D 0A"; int sLen=sizeof(sBuff);
   unsigned long iBytesRead, iBytesWritten;      printf("program start...(s=send, q=quit)\n");
   while (1)
   {  //READ:!!!!!!!!
      if (ReadFile(hCom, rBuff+rPos, rLen, &iBytesRead, NULL)) if (iBytesRead==1)
         printf("%02X", rBuff[rPos]); //todo: ++rPos ...rPos %=buffSize ...

      //WRITE (send) if userKey 'S' .. exit if 'Q'
      if (kbhit()) switch (getch()) {   case 's': case 'S':
                                           printf("\n...sending (%d) bytes", sLen);
                                           WriteFile(hCom, sBuff, sLen, &iBytesWritten, NULL);
                                           printf(" ...sent (%d) bytes.\n", iBytesWritten);
                                           break;
                                        case 'q': case 'Q': return 0;  }
   }
   return 0;
}