Configuring_the_Servos.md

Configuring the Servos

The goal of this preliminary step is:

1. reprogram the ST3215 Servos (I used the 12V, 30kg version) so each one has a different ID number
2. and then zero the servos.

The kit comes with two driver boards:

• Waveshare 25514 Serial Bus Servo Driver Board referred to in the official BOM
• the FE-URT-1 board ships as part of the ST3215 servo kit (and is also referred to in this video Standard Open ARM 100 5DOF Servos - Low cost DIY 3dprinted robot arm for Le Robot by Hugging Face)

Each board allows to follow a slightly different process to complete this step, with each of the two methods having pros and cons

Method 1 - Waveshare 25514 board	Method 2 - FE-URT-1 board
Requires installing the lerobot environment	Requires windows
Provides a basic CLI with very limited options (renaming and zeroing only)	Provides a nice debugging GUI that allows operating the servos and configuring many options
Requires that servos are connected to the PC one by one, so it does not work on the assembled robot	Works on the assembled robot with all the servos connected in daisy chain
The Waveshare board fits the 3D printed support and (presumably) works with lerobot software	The FE-URT-1 does not fit the 3D printed support, and it is not confirmed that will work with lerobot software

Method 1: using the Waveshare 25514 board

Install LeRobot

Followed instructions here: https://github.com/huggingface/lerobot/blob/main/examples/10_use_so100.md

Notes:

1. during miniconda installation I got a WARNING that PYTHONPATH environment variable is set and I should check all files in the path are compatible with python version in miniconda (??)

   Workaround - unset PYTHONPATH manually before activating conda:

$ unset PYTHONPATH
$ conda activate lerobot

It is also possible to automate this step modifying the conda environment activation script (not done)

2. After installation conda base environment activates automativally so when I open a terminal I get by default the prepend (base) $. I don't like this as I am not sure if the behaviour of my other projects (ROS, C++) may change under conda

   Workaround - prevent auto activation of base with:

$ conda config --set auto_activate_base false

Then I can activate it manually only when needed.

3. To note, the conda installer installed ffmpeg, and removed opencv and reinstalled it with conda

Configuring the servos

The video Assemble and Calibrate SO-100: LeRobot Tutorial #7 by Jess Moss describes servo configuration with the Waveshare board

Starting lerobot:

$ cd ~/lerobot
$ unset PYTHONPATH
$ conda activate lerobot

Detect the port:

(lerobot)$ python lerobot/scripts/find_motors_bus_port.py

Rename the servos:

(lerobot)$ python lerobot/scripts/configure_motor.py \
  --port /dev/ttyACM0 \
  --brand feetech \
  --model sts3215 \
  --baudrate 1000000 \
  --ID 1

Note: need to remove gears from the servos of the leader arm! (why buy the 30kg servos then?)

Note: The calibration script mentioned in the video does not exist.

Method 2: using the FE-URT-1 driver board

Resources

• The video Standard Open ARM 100 5DOF Servos - Low cost DIY 3dprinted robot arm for Le Robot by Hugging Face describes the connection and renaming steps, but skips the installation of the software, and is for the 6V version not the 12V one.

Step by step guide

1. Local copies of the required software can be found in folder ./Feetech_sfw_win or downloaded from Feetech website. Note both packages are for Windows OS:

   • the FE-URT-1 board driver CH341SER.EXE
   • the debugging GUI FD.EXE (version FD1.9.8.3)

2. Install the driver CH341SER.EXE

3. Connect the board to a 12V power supply and to the USB. Check switch is set to 5V. Connect the Servo. Note: Had to connect 12V input to G - V1 terminals, even though they are rated DC6V-8V. If I connect to G-V2 (rated 8V-24V) it would not work!! Did this by executive decision, I found nothing online.

2. Check in Device Manager under Ports: USB-SERIAL CH340 (COM4)
3. Install and launch FD.EXE
4. In Debug tab, set BaudR to 1000000, then click Open then Search to find the servos
5. Click on the detected Servo, go to tab Programming, select ID, rename to 6 , click Save
6. Connect another servo in daisy chain, repeat the process and rename it to 5, then 4, etc until 1.

7. In Debug tab, select the Sync Write toggle, set Goal to 2048 then click Set to zero all servos to the middle point.