LX-16A Bus Servo Examples for Raspberry Pi

This repository contains examples for how to program LX-16A bus servomotors on Raspberry Pi.

It also contains LX16A class taken from PyLX-16A package. This class is free from any Qt or other unnecessary dependencies. These examples can run on Raspberry Pi OS, any other Linux, or macOS. Perhaps, should work on Windows, but not tested on it.

Features

• Compatible with 3-pin LX-16A bus servo motors, and possibly with other servos of this family
• No need to install Qt, only pyserial
• Contains examples with smooth motion (easing in and out) in servo and motor modes: see osc.py, smoothmotor.py, smoothservo.py.

Requirements

• Raspberry Pi 4 or 5 [with GPIO]
• BusLinker, also known as the TTL/USB Debug Board for Serial Bus Servo
• External power for the motor

Installation

Put the files from this repository into your project directory on Raspberry Pi.
Install pyserial package (for Debian 12 / Raspberry Pi OS):

sudo apt install python3-serial

or (if you are using virtual environments):

pip3 install pyserial

LX16A class: most useful methods

Initialize the BusLinker:
LX16A.initialize(port: str, timeout: float = 0.02) -> None
On Raspberry Pi, the port is typically "/dev/ttyUSB0".

Create servo instances:
motor_obj = LX16A(id_: int, disable_torque: bool = False) -> None

Set the ID of the servo:
motor_obj.set_id(id_: int) -> None

Rotate to the given angle (for LX-16A from 0 to 240):
motor_obj.move(angle: float, time: int = 0, relative: bool = False, wait: bool = False) -> None

Enable torque so that it does not relax (prevents moving due to gravity or other forces):
motor_obj.enable_torque() -> None

Disable torque so that you can rotate it, for instance, with your hands:
motor_obj.disable_torque() -> None

Read the physical angle at which the servo is currently positioned:
motor_obj.get_physical_angle() -> float

Read the last commanded angle (not necessarily the same as physical angle):
motor_obj.get_commanded_angle() -> float

Set the servo to the motor mode (continuous rotation without positioning):
motor_obj.motor_mode(speed: int) -> None

Set the servo to the servo mode (positioning, no continuous rotation):
motor_obj.servo_mode() -> None

Turn on internal servo LED:
motor_obj.led_power_on() -> None

Turn off internal servo LED:
motor_obj.led_power_off() -> None

Check if the servo is in the motor mode:
motor_obj.is_motor_mode(poll_hardware: bool = False) -> bool

Check if torque is enabled:
motor_obj.is_torque_enabled(poll_hardware: bool = False) -> bool

Check if internal LED is on:
motor_obj.is_led_power_on(poll_hardware: bool = False) -> bool

Read the current temperature at the servo in °C:
motor_obj.get_temp(self) -> int

Read supplied voltage in millivolts:
motor_obj.get_vin(self) -> int

Example

See more examples and get smooth motion classes in other files in this repository.

import time
from lx16a import LX16A

# Setup:
try:
    LX16A.initialize("/dev/ttyUSB0")
except Exception as e:
    print("Initialisation ERROR")
    print(e)
    quit()

motor1 = LX16A(1)
motor2 = LX16A(2)

motor1.enable_torque()
motor1.servo_mode()

motor2.enable_torque()
motor2.servo_mode()

# Main loop:
try:
  while True:
    angle = motor1.get_physical_angle()
    time.sleep(0.05)
    print(f"angle: {angle:.2f}")

    motor1.move(240)
    time.sleep(1)

    motor2.move(240)
    time.sleep(2)

    angle = motor1.get_physical_angle()
    time.sleep(0.05)
    print(f"angle: {angle:.2f}")

    motor1.move(0)
    time.sleep(1)

    motor2.move(0)
    time.sleep(2)

except KeyboardInterrupt:
  print("Program stopped.")

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