serial_open.c

/*------------------------------------------------------------------------------
 * Open a serial port to the MAV with the given port name and baud rate.
 * returns: the file descriptor, or < 0 if error.
 */
static int mav_serial_open(const char *port_name, uint32_t const baud_rate)
{
  // attempt to open the port.
  int fd = open(port_name, O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd < 0) {
    fprintf(stderr, "ERROR: Could not open() serial port %s.\n", port_name);
    return fd;
  }

  // configure file reading.
  fcntl(fd, F_SETFL, 0);

  // set baud rate from parameter
  speed_t baud;
  switch (baud_rate) {
    case 115200:
      baud = B115200;
      break;
    default:
      baud = B57600;
      break;
  }

  // get previous options
  struct termios options;
  tcgetattr(fd, &options);

  // set baud rate in options
  int ret = cfsetispeed(&options, baud);
  if (ret < 0) {
    fprintf(stderr, "ERROR: Couldn't set speed for serial port %s\n", port_name);
    return ret;
  }

  ret = cfsetospeed(&options, baud);
  if (ret < 0) {
    fprintf(stderr, "ERROR: Couldn't set speed for serial port %s\n", port_name);
    return ret;
  }

  // set other flags in options
  // (raw i/o for 8N1)
  options.c_cflag &= ~(CSIZE | PARENB);
  options.c_cflag |= CS8 | CLOCAL | CREAD | CRTSCTS;
  options.c_lflag = ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
  options.c_oflag = ~(OCRNL | ONLCR | ONLRET | ONOCR | OFILL | OPOST);
  options.c_iflag = ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR |
      INPCK | ICRNL | IXON);
  options.c_cc[VMIN] = 1;

  // set attributes for serial port.
  ret = tcsetattr(fd, TCSAFLUSH, &options);
  if (ret < 0) {
    fprintf(stderr, "ERROR: Can't set attribs for serial port %s\n", port_name);
    return ret;
  }

  return fd;
}