sample read rs-232

**************************************************
* adrport.c
**************************************************

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <string.h>
#include <errno.h>
#include "adrport.h"
static int fd = 0;

// opens the serial port
// return code:
//   > 0 = fd for the port
//   -1 = open failed
int OpenAdrPort(char* sPortNumber)
{
    char sPortName[64];
	 system("clear");	 
	 printf("***************************************************************************\n"); 
	 printf("*                                                                         *\n");	 
	 printf("* Programa para leer el puerto Serial - Por: Coop. Linux Solutions, RL    *\n");  
	 printf("*                                                                         *\n");
	 printf("***************************************************************************\n");  
    printf("En Puerto (OpenAdrPort)#=%s\n", sPortNumber);
    sprintf(sPortName, "/dev/ttyS%s", sPortNumber);
    printf("Nombre del Puerto= %s\n", sPortName);

    // make sure port is closed
    CloseAdrPort(fd);

    fd = open(sPortName, O_RDWR | O_NOCTTY | O_NDELAY);
    if (fd < 0)
    {
        printf("Error al abrir el puerto %d %s\n", errno, strerror(errno));
    }
    else
    {
        struct termios my_termios;
        printf("fd es %d\n", fd);
        tcgetattr(fd, &my_termios);
        // NOTE: you may want to save the port attributes 
        //       here so that you can restore them later
        //printf("old cflag=%08x\n", my_termios.c_cflag);
        //printf("old oflag=%08x\n", my_termios.c_oflag);
        //printf("old iflag=%08x\n", my_termios.c_iflag);
        //printf("old lflag=%08x\n", my_termios.c_lflag);
        //printf("old line=%02x\n", my_termios.c_line);

        tcflush(fd, TCIFLUSH);
        
        my_termios.c_cflag = B9600 | CS8 |CREAD | CLOCAL | HUPCL;
        
        cfsetospeed(&my_termios, B9600);
        tcsetattr(fd, TCSANOW, &my_termios);
 
        //printf("new cflag=%08x\n", my_termios.c_cflag);
        //printf("new oflag=%08x\n", my_termios.c_oflag);
        //printf("new iflag=%08x\n", my_termios.c_iflag);
        //printf("new lflag=%08x\n", my_termios.c_lflag);
        //printf("new line=%02x\n", my_termios.c_line);
    } // end if
    return fd;
} // end OpenAdrPort

// writes zero terminated string to the serial port
// return code:
//   >= 0 = number of characters written
//   -1 = write failed
int WriteAdrPort(char* psOutput)
{
    int iOut;
    if (fd < 1)
    {
        printf(" port is not open\n");
        return -1;
    } // end if
    iOut = write(fd, psOutput, strlen(psOutput));
    if (iOut < 0)
    {
        printf("write error %d %s\n", errno, strerror(errno));
    }
    else
    {
    	printf("wrote %d chars: %s\n", iOut, psOutput);
    } // end if
    return iOut;
} // end WriteAdrPort

// read string from the serial port
// return code:
//   >= 0 = number of characters read
//   -1 = read failed
int ReadAdrPort(char* psResponse, int iMax)
{
    int iIn;
    printf("in ReadAdrPort iMax=%d\n", iMax);
    if (fd < 1)
    {
        printf(" port is not open\n");
        return -1;
    } // end if
    strncpy (psResponse, "N/A", iMax<4?iMax:4);
    iIn = read(fd, psResponse, iMax-1);
    if (iIn < 0)
    {
    	if (errno == EAGAIN)
    	{
		return 0; // assume that command generated no response
	}
	else
	{
		printf("read error %d %s\n", errno, strerror(errno));
	} // end if
    }
    else
    {
    	psResponse[iIn<iMax?iIn:iMax] = '\0';
	    printf("read %d chars: %s\n", iIn, psResponse);
    } // end if

    return iIn;
} // end ReadAdrPort

// closes the serial port
void CloseAdrPort()
{


***************************************************************
** adrserial.c
**************************************************************

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "adrport.h"  
            
// this is the mainline thingee
int main(int argc, char *argv[]) 
{ 
	char sCmd[254];
	char sResult[254];
	if (argc < 2 || argc > 2)
	{	
		printf("El adrserial requiere 1 parametro que especifique el puerto serial\n");
		printf("  ie. use 'adrserial 0' para conectarse a /dev/ttyS0\n");
		return 0;
	} // end if
	printf("Presione la tecla q para salir.\n\n");
	if (OpenAdrPort(argv[1]) < 0) return 0;
	while (1)
	{
		int iSpot;
		
		printf("Para salir presione la letra q:");
		gets(sCmd);
		if (sCmd[0] == 'q' || sCmd[0] == 'Q') return 0;
		iSpot = strlen(sCmd);
		//sCmd[iSpot] = 0x0d; // stick a <CR> after the command
		//sCmd[iSpot+1] = 0x00; // terminate the string properly
		//if (WriteAdrPort(sCmd) < 0) return 0;
		sleep(1); // give the ADR card some time to respond
		if (ReadAdrPort(sResult,254) > 0)
		{
			printf("La respuesta del puerto es %s\n", sResult);
		} // end if
	} // end while
	
	CloseAdrPort();

} // end main


************************************************************************
**  adrport.h
************************************************************************

// adrport.h
// Copyright MMI, MMII by Sisusypro Incorporated

int OpenAdrPort (char* sPortNumber);
int WriteAdrPort(char* psOutput);
int ReadAdrPort(char* psResponse, int iMax);
void CloseAdrPort();