Control.com - Nerds in Control

Sealevel Systems (http://www.sealevel.com) includes code samples on the software CD that ships with all serial products. This C++ code sample shows you how to open a COM port, and send & receive data. In this example, data is sent and read at 460K bps, but standard windows ports are limited to 115K bps.

----- Begin Code Sample -----

#include "stdafx.h"
#include 
#include 
#include 
int main(int argc, char* argv[])
{
    char INBUFFER[500];
    char OUTBUFFER[20];
    DWORD        bytes_read    = 0;    // Number of bytes read from port
    DWORD        bytes_written = 0;    // Number of bytes written to the port
    HANDLE       comport      = NULL;  // Handle COM port
 int   bStatus;
    DCB          comSettings;          // Contains various port settings
    COMMTIMEOUTS CommTimeouts;
    strcpy(&OUTBUFFER[0], "The quick brown fox jumped over the lazy dog. \n\r\0");
    // Open COM port
    if ((comport = 
         CreateFile("\\\\.\\COM5",                // open com5:
                    GENERIC_READ | GENERIC_WRITE, // for reading and writing
                    0,                            // exclusive access
                    NULL,                         // no security attributes
                    OPEN_EXISTING,              
                    FILE_ATTRIBUTE_NORMAL,
                    NULL)) == INVALID_HANDLE_VALUE)
    {
        // error processing code goes here
    }
    // Set timeouts in milliseconds
    CommTimeouts.ReadIntervalTimeout         = 0; 
    CommTimeouts.ReadTotalTimeoutMultiplier  = 0; 
    CommTimeouts.ReadTotalTimeoutConstant    = 100;
    CommTimeouts.WriteTotalTimeoutMultiplier = 0;
    CommTimeouts.WriteTotalTimeoutConstant   = 100;
    bStatus = SetCommTimeouts(comport,&CommTimeouts);
    if (bStatus != 0)
    {
        // error processing code goes here
    }
    // Set Port parameters.
    // Make a call to GetCommState() first in order to fill
    // the comSettings structure with all the necessary values.
    // Then change the ones you want and call SetCommState().
    GetCommState(comport, &comSettings);
    comSettings.BaudRate = 460800;
    comSettings.StopBits = ONESTOPBIT;
    comSettings.ByteSize = 8;
    comSettings.Parity   = NOPARITY;
    comSettings.fParity  = FALSE;
    bStatus = SetCommState(comport, &comSettings);
    if (bStatus == 0)
    {
        // error processing code goes here
    }
    while(!kbhit())
    {
  bStatus = WriteFile(comport,              // Handle
       &OUTBUFFER,      // Outgoing data
       48,              // Number of bytes to write
       &bytes_written,  // Number of bytes written
       NULL);
        if (bStatus != 0)
        {
            // error processing code here
        }
        bStatus = ReadFile(comport,   // Handle
                &INBUFFER,            // Incoming data
                500,                  // Number of bytes to read
                &bytes_read,          // Number of bytes read
                NULL);
        if (bStatus != 0)
        {
            // error processing code goes here
        }
        // code to do something with the data goes here
    }
    CloseHandle(comport);
 return 0;
}

// A ReadIntervalTimeout value of MAXDWORD, combined with zero values for both the ReadTotalTimeoutConstant 
        //   and ReadTotalTimeoutMultiplier members, specifies that the read operation is to return immediately with 
        //   the bytes that have already been received, even if no bytes have been received.

        CommTimeouts.ReadIntervalTimeout            = MAXDWORD; 
        CommTimeouts.ReadTotalTimeoutMultiplier     = 0;
        CommTimeouts.ReadTotalTimeoutConstant		= 0;
        CommTimeouts.WriteTotalTimeoutMultiplier	= 0;
        CommTimeouts.WriteTotalTimeoutConstant		= 0;