serial.c

/* Port configuration partially based on great example "Arduino-serial" by
 * Tod E. Kurt.
 * http://todbot.com/blog/2006/12/06/arduino-serial-c-code-to-talk-to-arduino/
 *
 * Header from Tod's source file:
 *
 * Created 5 December 2006
 * Copyleft (c) 2006, Tod E. Kurt, tod@todbot.com
 * http://todbot.com/blog/
 */


#define _BSD_SOURCE /* CRTSCTS */
#include <stdio.h>
#include <stdlib.h> 
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <sys/ioctl.h>

#include "serial.h"


/*
 * Open serial port from name and baud rate and return file desciptor.
 */
int serial_init(const char* serialport, int baud)
{
	struct termios toptions;

	int serial;
	speed_t brate;

	serial = open(serialport, O_RDWR | O_NOCTTY);

	if (serial == -1)
		return -1;

	if (tcgetattr(serial, &toptions) < 0)
		return -1;

	switch (baud) {
#ifdef B4800
		case 4800:
			brate=B4800;
			break;
#endif
#ifdef B9600
		case 9600:
			brate=B9600;
			break;
#endif
#ifdef B14400
		case 14400:
			brate=B14400;
			break;
#endif
#ifdef B19200
		case 19200:
			brate=B19200;
			break;
#endif
#ifdef B28800
		case 28800:
			brate=B28800;
			break;
#endif
#ifdef B38400
		case 38400:
			brate=B38400;
			break;
#endif
#ifdef B57600
		case 57600:
			brate=B57600;
			break;
#endif
#ifdef B115200
		case 115200:
			brate=B115200;
			break;
#endif
#ifdef B250000
		case 250000:
			brate=B250000;
			break;
#endif
#ifdef B230400
		case 230400:
			brate=B230400;
			break;
#endif
#ifdef B460800
		case 460800:
			brate=B460800;
			break;
#endif
#ifdef B500000
		case 500000:
			brate=B460800;
			break;
#endif
#ifdef B576000
		case 576000:
			brate=B576000;
			break;
#endif
		default:
			perror("Invalid baudrate");
			return -1;
	}

	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;

	/* turn on READ & ignore ctrl lines */
	toptions.c_cflag |= CREAD | CLOCAL;

	/* turn off s/w flow ctrl */
	toptions.c_iflag &= ~(IXON | IXOFF | IXANY);

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

	/* set blocking method */
	toptions.c_cc[VMIN] = SERIAL_VMIN;
	toptions.c_cc[VTIME] = SERIAL_VTIME;

	if (tcsetattr(serial, TCSANOW, &toptions) < 0)
		return -1;

	return serial;
}


/*
 * Read a complete line from the serial port
 */
int serial_getline(int serial, char *buffer, int timeout)
{
	int nbytes, i = 0;
	int retries = (timeout * 10) / SERIAL_VTIME;
	char byte[1];

	do {
		/* Block until one character received or timeout */
		nbytes = read(serial, byte, 1);

		/* Return if in error state */
		if (nbytes == -1)
			return -1;

		/* Try again if timed out */
		if (nbytes == 0) {
			retries--;
			continue;
		}

		/* Otherwise add the new byte to the buffer */
		buffer[i] = byte[0];
		i++;

	} while (byte[0] != '\n' && retries > 0);

	/* Remove end of line characters and null terminate the string */
	if (buffer[i - 2] == '\r')
		i -= 2;
	else
		i -= 1;

	buffer[i] = 0;

	return i;
}