Architecture

Parts

Part	Function
Servos J1–J6	Feetech STS bus servos, IDs 1–6, on one half-duplex bus at 1 Mbaud. Each servo runs its own position controller.
Base	Holds the 12 V input and an Arduino-style header. It bridges a UART on header pins 13/14 to the servo bus. The circuit inside is not known.
FT232R adapter	USB-serial adapter on the base pins. It gives the laptop direct access to the servo bus.
ATOM	M5Stack ATOM Matrix (ESP32-PICO-D4) at the end of the arm. It is on the servo bus (G19/G22). It has WiFi, a 5×5 LED matrix, a button and an IMU.
Laptop	Plans trajectories (Julia, RigidBodyDynamics.jl), plays them through the FT232R or uploads them to the ATOM, and analyses the recordings.

The two control paths

	Laptop path	ATOM path
Who runs the loop	Laptop (Julia or Python)	ATOM firmware, core 1
Link to the bus	USB → FT232R → base	Direct (G19/G22)
Loop rate	~285–320 Hz	500 Hz (fixed)
Timing jitter	Stalls of 6–80 ms (OS, USB, garbage collection)	±15 µs
Link to the laptop	USB cable	WiFi (UDP)
IMU data	No	Yes, every cycle

Both paths use the same plan format and produce the same recording columns. The ATOM recordings have six more columns for the IMU.

Coordinates and units

Joint angles are in degrees, with the same signs and zeros as the stock firmware’s get_angles. 0° on every joint is the upright pose.
Servo positions are in steps: 4096 steps per turn, 0° = step 2048. angle = sign × (step − 2048) × 360 / 4096, with sign [−1, −1, +1, −1, −1, −1] for J1–J6.
Cartesian positions are in millimetres in the base frame of the URDF.

Repository layout

Path	Contents
`src/`	Julia package `MyCobot`: kinematics, servo bus, FT232R control, players, ILC, ATOM link.
`scripts/`	Julia scripts: plan, play, trace, learn, analyse.
`test/`	Julia tests, including a simulated servo bus.
`firmware/`	ATOM firmware: `atom_controller` and `atom_probe`.
`tools/python/`	Python tools for the laptop path, plots and offline analysis.
`mycobot_description/`	URDF and meshes.
`website/`	This documentation site.