comms.cpp 3.02 KB
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 *   Copyright (c) 2013 PX4 Development Team. All rights reserved.
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 *    used to endorse or promote products derived from this software
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file comms.c
 * @author Simon Wilks <sjwilks@gmail.com>
 *
 */

#include "comms.h"

#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <systemlib/err.h>
#include <termios.h>

int
open_uart(const char *device)
{
	/* baud rate */
	static const speed_t speed = B19200;

	/* open uart */
	const int uart = open(device, O_RDWR | O_NOCTTY);

	if (uart < 0) {
		PX4_ERR("opening %s", device);
		return 1;
	}

	/* Back up the original uart configuration to restore it after exit */
	int termios_state;
	struct termios uart_config_original;

	if ((termios_state = tcgetattr(uart, &uart_config_original)) < 0) {
		close(uart);
		PX4_ERR("%s: %d", device, termios_state);
		return 1;
	}

	/* Fill the struct for the new configuration */
	struct termios uart_config;
	tcgetattr(uart, &uart_config);

	/* Clear ONLCR flag (which appends a CR for every LF) */
	uart_config.c_oflag &= ~ONLCR;

	/* Set baud rate */
	if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
		close(uart);
		PX4_ERR("%s: %d (cfsetispeed, cfsetospeed)", device, termios_state);
		return 1;
	}

	if ((termios_state = tcsetattr(uart, TCSANOW, &uart_config)) < 0) {
		close(uart);
		PX4_ERR("%s (tcsetattr)", device);
		return 1;
	}

	/* Activate single wire mode */
	ioctl(uart, TIOCSSINGLEWIRE, SER_SINGLEWIRE_ENABLED);

	return uart;
}