char receiveCommand() {

  int rx_length;
  int uart0_filestream = -1;
  char rx = '-';
  time_t startTime;
  time_t actualTime;

  uart0_filestream = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
  if (uart0_filestream == -1) {
    printf("[ERROR] UART open()\n");
    return '-';
  }

  struct termios options;
  tcgetattr(uart0_filestream, &options);
  options.c_cflag = B9600 | CS8 | CLOCAL | CREAD;
  options.c_iflag = IGNPAR;
  options.c_oflag = 0;
  options.c_lflag = 0;
  tcflush(uart0_filestream, TCIFLUSH);
  tcsetattr(uart0_filestream, TCSANOW, &options);

  // Bytes empfangen
  if (uart0_filestream != -1) {

    startTime = time(0);

    while(rx == '-') {
      actualTime = time(0);
      // 1 second to answer, otherwise timeout
      if(difftime(actualTime, startTime) > 3) {
	//return timeout
	return '#';
      }

      rx_length = read(uart0_filestream, &rx, 1);
    }

    if (rx_length < 0) {
      printf("%c", rx);
      rx = '-';
      return rx;

    } else if (rx_length == 0) {
      printf("%c", rx);
      rx = '-';
      return rx;
    }

    return rx;

  } //if uart0

  close(uart0_filestream);
  return rx;
}