MBOT Servo Library

This is a Python library for Dynamixel servos using DynamixelSDK.

This is compatible with Pi5 and only tested on Pi5. Curerntly tested with XL320, XL330-M288, XL430-W250.

Install

1. Edit the Configuration File.

   sudo nano /boot/firmware/config.txt

2. Add UART Overlay: Add the following lines to the end of the file to enable the primary UART on GPIO pins 14 (TX) and 15 (RX) :

   [pi5]
   dtoverlay=uart0-pi5

3. Run the following to add user to dialout group:

   sudo usermod -a -G dialout $USER

4. Reboot your Raspberry Pi for the changes to take effect.

   sudo reboot

5. Test. Run the following command we should see ttyAMA0 list

   $ ls /dev | grep ttyAMA
   ttyAMA0
   ttyAMA10
   

   Then run groups and you should see dialout listed.
6. Run the following install script

   cd ~/mbot_servo_lib
   ./install.sh

   • After installing the library, any script, anywhere, can do from mbot_servo_library import *

You are all set.

How to use

from mbot_servo_library.xseries_wrapper import BAUDRATE, Servo
# from mbot_servo_library.xl320_wrapper import BAUDRATE, Servo

• If you are using XL320, which is very unstable, you need to switch from xseries_wrapper to xl320_wrapper, they have different control table.
• If you are using XL330-M288 or XL430-W250, proceed.

1. Check the servo ID. This program will ping all the possible IDs and give you the list of connected IDs. Connect one servo to Pi at a time for ID checking.

   cd ~/mbot_servo_lib/tests
   python3 check_servo_id.py

2. Modify change_servo_id.py to change the ID if you use more than 1 servo, we need to avoid using identical ID for multiple servos. You may face communication failure or may not be able to detect a servo with an identical ID - Source.

   python3 change_servo_id.py

3. We have 3 examples tests/position_control.py, tests/extended_position_control.py, and tests/velocity_control.py. You need to define the servo ID to use them, and the ID is the one you obtain from step 1.

   python3 velocity_control.py

Uninstall

sudo pip3 uninstall dynamixel_sdk mbot_servo_library --break-system-packages

A few things

1. gpiod: Uses the native BCM (or GPIO) numbers. Unlike Jetson.GPIO (with GPIO.BOARD): Uses the physical pin numbers on the header.