//* sample C program that access a serial port com3 under Win32 *
#include<windows.h>
#include<stdio.h>
#include<string.h>

int main() {
    // declare a variable that describes com device parameters
    DCB dcbCOM;

    int OK;

    // declare the structure that describes a file or a device
    HANDLE hCOM = CreateFile(
        TEXT("COM3"),                   // file or device name
        GENERIC_READ|GENERIC_WRITE,     // access mode: can read and/or write
        0,                              // sharing mode
        NULL,                           // security attributes
        OPEN_EXISTING,                  // whether to create a new file
        0,                              // file attributes to set,
        NULL);                          // template file handle

    if (hCOM==INVALID_HANDLE_VALUE) {
        fprintf(stderr, "ERROR: cannot create COM device handle\n");
        return(0);
    }


    // initialize COM port
    // get the current COM device parameters
    OK=GetCommState(hCOM, &dcbCOM);
    if (OK) {
        // modify the parameters to suit our needs
        dcbCOM.BaudRate = 9600;
        dcbCOM.ByteSize = 8;
        dcbCOM.Parity = NOPARITY;
        dcbCOM.StopBits = ONESTOPBIT;
        // set the COM device parameters according to that variable
        OK=SetCommState(hCOM, &dcbCOM);
        if (OK) {
            // set the internal input and output buffer
            OK=SetupComm(hCOM, 2048, 1024);
            if (OK) {
                // setup area to keep data
                char buffer[1024];
                DWORD size=0;
                DWORD done;

                for (;;) {
                    fgets(buffer, sizeof(buffer), stdin);
                    if (strcmp(buffer,".\n")==0) break;
                    buffer[strlen(buffer)]=0;
                    strcat(buffer, "\r\n");

                    /* */
                    // SAMPLE WRITE
                    // write some data to the file or device
                    OK=WriteFile(hCOM,                  // file or device handle
                        &buffer,                        // address of buffer with data to send
                        strlen(buffer),                 // how many bytes should be sent
                        &done,                          // how many bytes were actually written
                        NULL);                          // NULL or Overlapped structure if used

                    if (!OK) fprintf(stderr, "ERROR: cannot write to COM port\n");

                    // make sure that everything from internal buffer is sent
                    OK=FlushFileBuffers(hCOM);
                    if (!OK) fprintf(stderr, "ERROR: cannot flush COM port\n");

                    // they may be actually sent after flushing
                    // because of the non-full buffer of 1024 bytes
                    // buffers speed your program in general though
                    fprintf(stdout, "%d bytes sent\n", done);
                    /* end of comment */

                    Sleep(500); // allow for processing by the embedded device

                    /* */
                    // SAMPLE READ - !!this will return whatevedr is in the buffer as long as there is at least one byte, otherwise, it waits!!
                    ReadFile(hCOM,                      // file or device handle
                        &buffer,                        // address of buffer to put received data
                        strlen(buffer),                 // how many bytes are expected
                        &done,                          // how many bytes were actually received
                        NULL);                          // must be NULL, not supported

                    buffer[done]=0; // Note: last byte in [done-1]
                    fprintf(stdout, "%s\n", buffer);

                    /* end of comment */
                }

            } else fprintf(stderr, "ERROR: cannot set buffer size for COM port\n");
        } else fprintf(stderr, "ERROR: cannot initialize COM port parameters\n");
    } else fprintf(stderr, "ERROR: cannot create COM port parameters record \n");

    // release device back to the Operating System
    CloseHandle(hCOM);

    return(0);
}