firmata-client-mcp

An MCP (Model Context Protocol) server that lets an LLM control an Arduino's GPIO over the Firmata protocol.

Built on the MCP Python SDK and the firmata-client library. It exposes digital/analog I/O, PWM, and basic servo control as MCP tools so an agent can read sensors and drive actuators on a connected board.

⚠️ This server lets an AI agent drive physical hardware. Please read the Safety section before connecting a board.

Features

• Discover serial ports and connect to a board running StandardFirmata
• Query board capabilities (firmware, pin modes, analog mapping)
• Digital read / write
• Analog (ADC) read with sample averaging
• PWM (analog) write
• Servo control with a settable "origin" reference point
• Structured JSON responses and actionable error messages

Requirements

• Python 3.13+ (required by the firmata-client dependency)
• An Arduino (or compatible board) flashed with StandardFirmata (File → Examples → Firmata → StandardFirmata in the Arduino IDE)
• Python dependencies:
  • mcp[cli] 2.x (v0.2.0 and later; use firmata-client-mcp 0.1.x if you are pinned to mcp 1.x)
  • firmata-client
  • pyserial (installed with firmata-client)
  • pydantic (installed with mcp)

Installation

Using uv (recommended):

uv pip install firmata-client-mcp

Or via pip:

pip install firmata-client-mcp

Or from source:

git clone https://github.com/NaoNaoMe/firmata-client-mcp.git
cd firmata-client-mcp
uv sync

Configuration

Claude Desktop Config

Add the server to your claude_desktop_config.json:

{
  "mcpServers": {
    "firmata-client-mcp": {
      "command": "uvx",
      "args": [
        "firmata-client-mcp"
      ]
    }
  }
}

A typical first interaction:

1. arduino_list_ports - find your board's serial port
2. arduino_connect - connect using that port
3. arduino_get_board_info - inspect supported modes per pin
4. arduino_set_pin_mode - configure a pin (e.g. pin 13 -> OUTPUT)
5. arduino_digital_write - turn it on

Tools

A note on pin vs. analog channel

arduino_analog_read takes an analog channel number (0 = A0, 1 = A1, …), but arduino_set_pin_mode expects the digital pin number. Use the analog_mapping returned by arduino_get_board_info to translate between them.

A note on servo movement

arduino_servo_move moves the servo to origin + value degrees (clamped to 0-180), where origin is whatever you registered with arduino_set_servo_origin (default 0). The move is relative to the origin, not cumulative - calling it twice with the same value results in the same physical position.

Safety

This server gives an autonomous agent direct control of electrical outputs and moving parts. Before use:

• Supervise it. Do not run it unattended while a board with actuators is powered.
• Mind your wiring. An agent can set any configured pin HIGH or drive PWM/servos; verify current limits, and mechanical end-stops yourself.
• Setting SERVO mode does not define a position. The physical angle right after a mode change is undefined and hardware-dependent.
• The author(s) accept no liability for damage to hardware or surroundings. Use at your own risk.

Limitations

• Single board / single client at a time (module-level connection state, no locking - intended for local stdio use).
• Pin numbers are accepted in the range 0-69 (covers boards up to Arduino Mega); the actual valid range depends on your board.
• Reads block briefly (~100 ms) while sampling.

License

This project is licensed under the MIT License - see the LICENSE file for details.