Plesty Arduino Firmata

A PLESTY device module for any board running the stock StandardFirmata sketch — Arduino Uno, Mega and the like. It drives the board's pins over USB serial: digital outputs and inputs, PWM, hobby servos and analog inputs.

The module knows pins, not instruments. An instrument wired to the board — a polarization controller, a motor driver — gets its own module that builds on this one and gives the pins their meaning (for example plesty-pcd-m02).

Prepare the board

Upload StandardFirmata once, from the Arduino IDE: File → Examples → Firmata → StandardFirmata. No other sketch is needed; this module speaks the public Firmata protocol at 57600 baud.

Installation

git clone https://gitlab.com/plesty/hub/devices/arduino/plesty-arduino-firmata.git
cd plesty-arduino-firmata
uv sync

On Linux, add your user to the dialout group for serial access (sudo usermod -aG dialout $USER, then log in again).

Usage

from plesty.arduino_firmata import Device

with Device(port="auto") as board:  # or "COM5", "/dev/ttyACM0", a USB serial number
    print(board.identity())  # StandardFirmata.ino 2.5 (Firmata) on COM5

    board.set_pin_modes([22, 23], "output")
    board.write_digital_pins(pins=[22, 23], levels=[True, False])

    board.set_pin_mode(pin=5, mode="input_pullup")
    print(board.read_digital(pin=5))  # {'level': True}
    print(board.read_analog(channel=0))  # {'counts': 512}

port="auto" picks the one genuine Arduino attached and refuses when there are none or several. A clone with a CH340 USB chip is not recognised — name its port or serial number instead.

Opening a session resets the board: every pin starts in the sketch's default and must be given a mode before it is written or read. Firmata cannot report an output pin back, so read_digital on an output answers the level this session last wrote.

port="mock" runs everything against a simulated Arduino Mega, no board needed.

Run as TCP server

Copy .env.example to .env and set DEVICE_ADDRESS, then:

uv run python -m plesty.arduino_firmata --tcp-port 5555

Open the control panel

uv sync --extra gui
uv run python -m plesty.arduino_firmata --gui

--gui drives the board from this process instead of serving it — one session is all the serial port allows, so the process does one or the other.