Python

Py-CmdMessenger

Pythonic port of the C#/VB CommandMessenger library for Arduino serial communication.

Architecture: see ../../plans/architecture-comparison.md Inspired by PyCmdMessenger (harmsm).

Status

🚧 Alpha — feature-complete, actively tested.

Setup

build.bat          # Windows
bash build.sh      # macOS / Linux

This creates .venv/, installs runtime dependencies, and installs the py-cmdmessenger package in editable mode so samples can import cmd_messenger.

If you're behind a corporate pip proxy that doesn't mirror all packages, override the index by setting PIP_INDEX_URL first:

set PIP_INDEX_URL=https://pypi.org/simple   # Windows
export PIP_INDEX_URL=https://pypi.org/simple # macOS/Linux
build.bat

Structure

Path	Purpose
cmd_messenger/	The library — import as import cmd_messenger
cmd_messenger/transport/	Pluggable transports (serial, network, etc.)
pyproject.toml	Package metadata (hatchling build backend)
requirements.txt	Dev environment dependencies
samples/	Sample applications (see samples/README.md)
samples/shared/	Sample helpers — console_utils.py, web_form.py
tests/	pytest suite (unit + hardware-in-the-loop)
tests/board_discovery.py	Auto-discovers connected boards (mirrors C# BoardDiscovery.cs)

Quick example

from cmd_messenger import CmdMessenger, SendCommand, BoardType
from cmd_messenger.transport.serial import SerialTransport, SerialSettings

settings = SerialSettings(port_name="COM6", baud_rate=115200)
transport = SerialTransport(settings)

with CmdMessenger(transport, board_type=BoardType.BIT_16) as messenger:
    messenger.connect()
    messenger.send_command(SendCommand(0, "Hello Arduino"))

Testing

Unit tests (no hardware needed)

pytest tests/ -m "not hardware"

Hardware-in-the-loop tests

Requires a board running test/integration/sketch/src/LoopbackTestRunner.ino.

Board auto-discovery mirrors C# BoardDiscovery.cs:

• Phase 1: USB VID:PID matching (Teensy, ESP32-S3)
• Phase 2: Serial kWhoAmI query for CH340 boards (Nano, ESP8266)

# Run all hardware tests (auto-discovers connected boards)
pytest --hardware -m hardware

# Run tests for a specific board
pytest --hardware -k "NANO"

Legacy single-board override (skips auto-discovery):

set CMDMESSENGER_PORT=COM3
pytest --hardware -m hardware

License

MIT — same as the parent C# library. © 2026 Thijs Elenbaas.