c++ serijski port

#include <unistd.h>
#include <fcntl.h>
#include <termios.h>

#include <string.h>
#include <errno.h>
#include <stdio.h>

#define SET_MASK(var, mask, bits) var = ((var) & ~(mask)) | ((bits) & (mask))
#define SET_BITS(var, mask) var |= ~(mask)
#define CLR_BITS(var, mask) var &= ~(mask)

/*
 * serial_setparam:
 *      fd          - this is the file descriptor of the serial port
 *      baudrate    - the desired baud rate, currently only 2400 bauds is
 *                    supported
 *      bits        - bit size, valid values are from 5 to 8 bits.
 *      parity      - this can be either 'N', 'E' or 'O' with the following
 *                    meanings:
 *                          'N' - NO PARITY
 *                          'E' - EVEN PARITY
 *                          'O' - ODD PARITY
 *      stopbits    - either 1 or 2, representing the number of stop bits
 *      softflow    - boolean, 0 for hardware flow control, 1 for software
 */
int serial_setparam(int fd, int baudrate, int bits, char parity, int stopbits, int softflow)
{
    struct termios tc;
    int    retval;

    /* GET ATTRIBUTES */
    retval = tcgetattr(fd, &tc);
    if (retval != 0)
    {
        fprintf(stderr, "tcgetattr() failed: %s\n", strerror(errno));
        return 1;
    }

    /* SET BAUD RATE */
    /* XXX: This sucks ;) */
    if (baudrate != 2400)
    {
        fprintf(stderr, "Unsupported baud rate %d\n", baudrate); 
        return 1;
    }

    retval = cfsetspeed(&tc, B2400);
    if (retval != 0)
    {
        fprintf(stderr, "cfsetspeed() failed: %s\n", strerror(errno));
        return 1;
    }

    /* CLEAR ALL FLAGS */
    CLR_BITS(tc.c_cflag, PARENB | PARODD | CSIZE | CSTOPB);

    /* SET BITS */
    switch (bits)
    {
        case 5:
            SET_BITS(tc.c_cflag, CS5);
            break;

        case 6:
            SET_BITS(tc.c_cflag, CS6);
            break;

        case 7:
            SET_BITS(tc.c_cflag, CS7);
            break;

        case 8:
            SET_BITS(tc.c_cflag, CS8);
            break;

        default:
            fprintf(stderr, "Unsupported bit size: %d\n", bits);
            return 1;
    }
    /* SET PARITY */
    switch (parity)
    {
            /* Disable parity */
            case 'N':
                /* Nothing to do */
                break;

            /* Enable parity, EVEN */
            case 'E':
                SET_BITS(tc.c_cflag, PARENB);
                break;

            /* Enable parity, ODD */
            case 'O':
                SET_BITS(tc.c_cflag, PARENB | PARODD);
                break; 

            default:
                fprintf(stderr, "Unsupported parity: it souhld be 'N' - none, 'E' -even, 'O' - odd\n");
                return 1;
    }

    /* SET STOP BITS */
    switch (stopbits)
    {
        case 1:
            /* Nothing to do */
            break;

        case 2:
            SET_BITS(tc.c_cflag, CSTOPB);
            break;

        default:
            fprintf(stderr, "Unsupporte stopbits number %d, use either 1 or 2\n", stopbits);
            return 1;
    }

    /*
     * ADDITIONAL STUFF: I'm not really sure why is this needed, I just copied
     * the stuff from minicom
     */

    /* Set line to RAW, NOECHO mode */
    tc.c_iflag = IGNBRK; /* IGNBRK, ignore break condition */
    tc.c_lflag = 0;
    tc.c_oflag = 0;
    /* CLOCAL, ignore modem status line. CREAD, enable receiver, CRTSCTS, CTS
     * flow control of output */
    SET_BITS(tc.c_cflag, CLOCAL | CREAD | CRTSCTS);

    tc.c_cc[VMIN]  = 1; /* Minimum bytes recevied    */
    tc.c_cc[VTIME] = 5; /* Read delay in 0.1 seconds */

    /* Software flow control */
    if (softflow)
    {
        SET_BITS(tc.c_iflag, IXON | IXOFF);
    }
    else
    {
        CLR_BITS(tc.c_iflag, IXON | IXOFF | IXANY);
    }

    /* FINALLY, SET ATTRIBUTES */
    retval = tcsetattr(fd, TCSANOW, &tc);
    if (retval != 0)
    {
        fprintf(stderr, "tcsetattr() failed: %s\n", strerror(errno));
        return 1;
    }

    return 0;
}

int main(void)
{
    int retval;
    int serial;
    int ii;

    serial = open("/dev/ttys0", O_RDWR);
    if (serial < 0)
    {
        fprintf(stderr, "cannot open /dev/ttys0: %s\n", strerror(errno));
        return 1;
    }

    /* Set serial port parameters: 2400 baud, None parity, 1 stop bit, no
     * software flow control */
    retval = serial_setparam(serial, 2400, 8, 'N', 1, 0);
    if (retval != 0)
    {
        fprintf(stderr, "serial_setparam() failed, exiting ...\n");
        return 1;
    }

    for (ii = 0; ii < 99; ii++)
    {
        char c;

        c = ii;
        retval = write(serial, &c, sizeof(c));
        if (retval < 0)
        {
            fprintf(stderr, "write() failed: %s\n", strerror(errno));
            return 1;
        }

        sleep(1); /* 1 second delay between writes */
    }

    close(serial);

    return 0;
}