MCP/U

The Unified Interface for AI-Ready Microcontrollers

Transform any Arduino-compatible MCU into an AI-controllable device via the Model Context Protocol.

By 2edge.co

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How It Works

┌─────────────────┐         ┌──────────────────────┐         ┌───────────────┐
│  Claude / Gemini│◄──MCP──►│  mcpu-client (npm)   │◄─Serial─►  MCU Firmware │
│  or any LLM     │  stdio  │  Dynamic tool regist. │  /TCP   │  McpIot lib   │
└─────────────────┘         └──────────────────────┘         └───────────────┘

1. Client connects to MCU over Serial or TCP
2. Client calls list_tools — MCU responds with its tool + pin registry (JSON Schema)
3. Client dynamically registers one MCP tool per MCU tool — zero hardcoded names
4. Your AI agent can now call any MCU tool by name

---

Quick Start

1 — Flash Firmware

cd firmware
pio run -t upload

Or open firmware/ in Arduino IDE and upload src/main.cpp.

2 — Add to your AI agent

No local setup needed — the client is on npm.

Claude Code:

claude mcp add mcpu -e SERIAL_PORT=/dev/ttyACM0 -- npx mcpu-client

Claude Desktop (~/.config/claude/claude_desktop_config.json):

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

Gemini CLI (~/.gemini/settings.json):

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

OpenCode (opencode.json):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "mcpu": {
      "type": "local",
      "command": ["npx", "mcpu-client"],
      "enabled": true,
      "environment": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

Windows — replace port with COM3, COM4, etc.

---

Firmware API

#include <McpIot.h>

McpDevice mcp("my-device", "1.0.0");

void setup() {
  mcp.add_pin(2,  "led",    MCP_DIGITAL_OUTPUT, "Status LED");
  mcp.add_pin(34, "sensor", MCP_ADC_INPUT,      "Analog Sensor");
  mcp.add_pin(18, "motor",  MCP_PWM_OUTPUT,     "Motor speed");

  mcp.add_tool("beep", "Play a tone", beep_handler);

  mcp.begin(Serial, 115200);
}

void loop() {
  mcp.loop();
}

Pin Types

Constant	Arduino API	Description
MCP_DIGITAL_OUTPUT	digitalWrite	LED, relay, buzzer
MCP_DIGITAL_INPUT	digitalRead	Button, reed switch
MCP_PWM_OUTPUT	analogWrite	Motor, servo, dimmer
MCP_ADC_INPUT	analogRead	Sensor, potentiometer

Custom Tool Handler

void my_handler(int id, JsonObject params) {
  int value = params["value"].as<int>();

  JsonDocument res;
  res["result"]["ok"] = true;
  mcp.send_result(id, res);
}

---

Built-in Tools

Tool	Parameters	Description
list_tools	—	Discovery: tools + pin registry
get_info	—	Device name, version, platform
gpio_write	pin, value (bool)	Set digital output HIGH/LOW
gpio_read	pin	Read digital level
pwm_write	pin, duty (0–255)	PWM output via analogWrite
adc_read	pin	Read ADC value (0–4095)

---

Client Environment Variables

Variable	Description	Default
SERIAL_PORT	Serial port path	—
SERIAL_BAUD	Baud rate	115200
DEVICES	Multi-device config string	—

---

Multi-Device Setup

Use the DEVICES env var with comma-separated entries:

DEVICES=robot:/dev/ttyUSB0:115200,display:/dev/ttyACM0:115200 npx mcpu-client

Format: id:port:baud (serial) or id:host:port:tcp (TCP)

With multiple devices, tools are named {device_id}__{tool_name} (e.g. robot__gpio_write).

---

Project Structure

├── firmware/               ESP32 firmware (PlatformIO project)
│   ├── src/main.cpp        Example firmware
│   └── lib/McpIot/         McpIot Arduino library
├── client/                 Universal MCP client (TypeScript, published on npm)
│   └── src/
│       ├── index.ts        Dynamic MCP server
│       ├── transport.ts    Serial + TCP transports
│       ├── device_manager.ts
│       └── schema_builder.ts
├── examples/               Firmware examples
│   ├── bme280-sensor/      Temperature, humidity, pressure
│   ├── ssd1306-display/    OLED display
│   ├── mpu6050-motion/     Gyroscope & accelerometer
│   └── lcd1604-display/    LCD 16x4 I2C
└── docs-site/              Starlight documentation site

---

License

LGPL v3 — Modifications to this library must remain open source. Products using it may be closed source.

By 2edge.co