comms.cpp

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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;
}