           strcat(serial_out, tmp_serial_out);
           i += 5;
         }
-        else if (tmp_str[i + 1] == 'U' || tmp_str[i + 1] == 'u') { // get potentiometer min max home
+        else if (tmp_str[i + 1] == 'U' || tmp_str[i + 1] == 'u') { // get ultrasound trig_pin echo_pin
           int ultrasound_index;
           byte trig_pin, echo_pin;
           sscanf(tmp_str + i + 2, "%d", &ultrasound_index);

      }

      if (tmp_str[i] == 'G' || tmp_str[i] == 'g') { // for debugging purpose
        if (tmp_str[i + 1] == 'S' || tmp_str[i + 1] == 's') { // gets stepper motor speed and acceleration
          int motor_index;
          byte num_sensors;
          float motor_speed, motor_acceleration;
          sscanf(tmp_str + i + 2, "%d", &motor_index);
          stepper_motors_controller.get_speed_and_acceleration(motor_index, &motor_speed, &motor_acceleration);
          num_sensors = stepper_motors_controller.get_num_attached_sensors(motor_index);
          sprintf(tmp_serial_out, "GS%d %d %d %d#", motor_index, (int)motor_speed, (int)motor_acceleration, num_sensors);
          strcat(serial_out, tmp_serial_out);
          i += 4;
        }

  Serial.println(F("Px# // Gets the position of the potentiometer x. Outputs Px p#"));
  Serial.println(F("Ix# // Gets the value of infrared sensor x. Outputs Ix v#"));

  Serial.println(F("GSx# // Gets the parameters for stepper motor x: speed acceleration num_sensors_attached. Outputs GSx s a 1#"));
  Serial.println(F("GDx# // Gets the parameters for dc motor x: speed num_sensors sensor_index1, sensor_type1 sensor_index1, sensor_type1. Outputs GDx s a 1 0 0#"));
  Serial.println(F("GPx# // Gets the parameters for potentiometer x: min max home direction. Outputs GPx n u h d#"));
  Serial.println(F("GUx# // Gets the parameters for ultrasound x: trig_pin echo_pin. Outputs GUx t e#"));
  Serial.println(F("GBx# // Gets the parameters for button x: out_pin direction. Outputs GBx p d#"));

  Serial.println(F("CS n d1 s1 e1 d2 s2 e2# // Creates the stepper motors controller and set some of its parameters. n is the number of motors, d, s, e are dir, step and enable pins. Outputs CS# when done."));
  Serial.println(F("CD n p1 d11 d12 e1 p2 d21 d22 e2# // Creates the dc motors controller and set some of its parameters. n is the number of motors, p is the pwm_pin, d1 and d2 are the direction pins and e is the enable pins. Outputs CD# when done."));
