arduinoserialposix.h

/* 
 * File:   arduinoserialposix.h
 * Author: riccardotacconi
 *
 * Created on December 21, 2010, 11:59 PM
 *
 *
 * Code derived from the example of  Tod E. Kurt, tod@todbot.com
 * http://todbot.com/blog/
 */

#include <stdio.h>    /* Standard input/output definitions */
#include <stdlib.h>
#include <stdint.h>   /* Standard types */
#include <string.h>   /* String function definitions */
#include <unistd.h>   /* UNIX standard function definitions */
#include <fcntl.h>    /* File control definitions */
#include <errno.h>    /* Error number definitions */
#include <termios.h>  /* POSIX terminal control definitions */
#include <sys/ioctl.h>
#include <getopt.h>

int serialport_init(const char* serialport, int baud);
int serialport_writebyte(int fd, uint8_t b);
int serialport_write(int fd, const char* str);
int serialport_read_until(int fd, char* buf, char until);
int delay(long milliseconds);

int serialport_writebyte( int fd, uint8_t b) {
    int n = write(fd,&b,1);
    if( n!=1)
        return -1;
    return 0;
}

int serialport_write(int fd, const char* str) {
    int len = strlen(str);
    int n = write(fd, str, len);
    if( n!=len )
        return -1;
    return 0;
}

int serialport_read_until(int fd, char* buf, char until) {
    char b[1];
    int i=0;
    do {
        int n = read(fd, b, 1);  // read a char at a time
        if( n==-1) return -1;    // couldn't read
        if( n==0 ) {
            usleep( 10 * 1000 ); // wait 10 msec try again
            continue;
        }
        buf[i] = b[0]; i++;
    } while( b[0] != until );

    buf[i] = 0;  // null terminate the string
    return 0;
}

// takes the string name of the serial port (e.g. "/dev/tty.usbserial","COM1")
// and a baud rate (bps) and connects to that port at that speed and 8N1.
// opens the port in fully raw mode so you can send binary data.
// returns valid fd, or -1 on error
int serialport_init(const char* serialport, int baud) {
    struct termios toptions;
    int fd;

    //fprintf(stderr,"init_serialport: opening port %s @ %d bps\n",
    //        serialport,baud);

    fd = open(serialport, O_RDWR | O_NOCTTY | O_NDELAY);
    if (fd == -1)  {
        perror("init_serialport: Unable to open port ");
        return -1;
    }

    if (tcgetattr(fd, &toptions) < 0) {
        perror("init_serialport: Couldn't get term attributes");
        return -1;
    }
    speed_t brate = baud; // let you override switch below if needed
    switch(baud) {
    case 4800:   brate=B4800;   break;
    case 9600:   brate=B9600;   break;
#ifdef B14400
    case 14400:  brate=B14400;  break;
#endif
    case 19200:  brate=B19200;  break;
#ifdef B28800
    case 28800:  brate=B28800;  break;
#endif
    case 38400:  brate=B38400;  break;
    case 57600:  brate=B57600;  break;
    case 115200: brate=B115200; break;
    }
    cfsetispeed(&toptions, brate);
    cfsetospeed(&toptions, brate);

    // 8N1
    toptions.c_cflag &= ~PARENB;
    toptions.c_cflag &= ~CSTOPB;
    toptions.c_cflag &= ~CSIZE;
    toptions.c_cflag |= CS8;
    // no flow control
    toptions.c_cflag &= ~CRTSCTS;

    toptions.c_cflag |= CREAD | CLOCAL;  // turn on READ & ignore ctrl lines
    toptions.c_iflag &= ~(IXON | IXOFF | IXANY); // turn off s/w flow ctrl

    toptions.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); // make raw
    toptions.c_oflag &= ~OPOST; // make raw

    // see: http://unixwiz.net/techtips/termios-vmin-vtime.html
    toptions.c_cc[VMIN]  = 0;
    toptions.c_cc[VTIME] = 20;

    if( tcsetattr(fd, TCSANOW, &toptions) < 0) {
        perror("init_serialport: Couldn't set term attributes");
        return -1;
    }

    return fd;
}

int delay(long milliseconds) {
    usleep(milliseconds * 1000 ); // sleep milliseconds
}