serial port initialization routines

serial_init.c

#define BAUD_2400 B2400
#define BAUD_4800 B4800
#define BAUD_9600 B9600
#define BAUD_38400 B38400
#define BAUD_57600 B57600
#define BAUD_115200 B115200


static int tty_attrib_conf(int fd, int speed, int parity) {
	struct termios tty;
	memset (&tty, 0, sizeof(tty));
	
	if (tcgetattr (fd, &tty) != 0) {
		fprintf(stderr, "Error %d from tcgetattr\n", errno);
		return -1;
	}

	// set I/O tty speed
	cfsetospeed (&tty, speed);
	cfsetispeed (&tty, speed);

	// 8-bit chars;
	tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;

	// disable IGNBRK for mismatched speed tests; otherwise receive break as \000 chars
	// ignore break signal
	tty.c_iflag &= ~IGNBRK;         

	// no signaling chars, no echo,
	tty.c_lflag = 0;

	// no canonical processing
	// no remapping, no delays
	tty.c_oflag = 0; 

	// read doesn't block
	tty.c_cc[VMIN]  = 0; 

	// 0.5 seconds read timeout
	tty.c_cc[VTIME] = 5; 

	// shut off xon/xoff ctrl
	tty.c_iflag &= ~(IXON | IXOFF | IXANY); 

	// ignore modem controls,
	tty.c_cflag |= (CLOCAL | CREAD);

	// enable reading / shut off parity
	tty.c_cflag &= ~(PARENB | PARODD);
	tty.c_cflag |= parity;
	tty.c_cflag &= ~CSTOPB;
	tty.c_cflag &= ~CRTSCTS;

	if (tcsetattr (fd, TCSANOW, &tty) != 0) {
		fprintf(stderr, "Error %d from tcsetattr\n", errno);
		return -1;
	}
	return 0;
}


/**
 * @brief whether a port should block (read() will block until the requested amount of bytes is received) or not
 *
 * @param fd port descriptor
 * @param should_block 1 - should block, 0 shouldn't
 */
static void tty_block_conf(int fd, int should_block) {
	struct termios tty;
	memset (&tty, 0, sizeof tty);

	if (tcgetattr (fd, &tty) != 0) {
		fprintf(stderr, "Error %d from tcgetattr\n", errno);
		return;
	}

	tty.c_cc[VMIN]  = should_block ? 1 : 0;
	tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout

	if (tcsetattr (fd, TCSANOW, &tty) != 0) {
		fprintf(stderr, "Error %d setting term attributes\n", errno);
		return;
	}
}