Firmware Server

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Firmware MCP Server is a local stdio MCP server for embedded firmware automation. It exposes a small set of tools that let an MCP client build firmware, flash devices, reset devices, and collect timestamped serial logs through commands defined in a local device configuration file.

The server is designed for workstation-local automation. It does not start an HTTP service, does not execute commands through a shell, and keeps local device paths out of version control by default.

Features

• Stdio-only MCP server for local clients.
• Four firmware-oriented tools: build, flash, reset, and serial log capture.
• Per-device async locks, so operations for the same device are serialized.
• Concurrent operation across different devices.
• Config hot reload when the device config file changes.
• Subprocess execution through asyncio.create_subprocess_exec.
• Command arguments are explicit arrays and are never passed to shell=True.
• Serial capture through pyserial, with incremental JSON trace events on stderr.
• Consistent JSON response envelope for success and failure cases.
• Lightweight deterministic diagnostics based on tool traces and serial log patterns.

Tools

Tool	Purpose
build_firmware	Run the configured build command for a device.
flash_firmware	Run the configured flash command for a device.
reset_device	Run the optional reset command for a device.
read_serial_log	Read timestamped serial lines from a device.

build_firmware, flash_firmware, and reset_device accept:

{
  "device_id": "demo",
  "timeout_ms": 300000
}

timeout_ms is optional.

read_serial_log accepts:

{
  "device_id": "demo",
  "duration_ms": 3000,
  "max_lines": 500
}

duration_ms and max_lines are optional.

Response Format

Every tool returns one JSON object encoded as MCP text content.

Success:

{
  "ok": true,
  "data": {},
  "error": null
}

Validation or runtime failure:

{
  "ok": false,
  "data": null,
  "error": {
    "error_type": "VALIDATION_ERROR",
    "type": "VALIDATION_ERROR",
    "message": "device_id must be a non-empty string",
    "recoverable": true
  }
}

Command failures keep captured process details in data:

{
  "ok": false,
  "data": {
    "device_id": "demo",
    "action": "build_firmware",
    "started_at": "2026-01-01T00:00:00.000Z",
    "finished_at": "2026-01-01T00:00:02.000Z",
    "command": ["make"],
    "cwd": "/path/to/project",
    "exit_code": 2,
    "timed_out": false,
    "stdout": "",
    "stderr": "make error"
  },
  "error": {
    "error_type": "BUILD_FAILED",
    "type": "BUILD_FAILED",
    "message": "build_firmware exited with code 2 for device: demo",
    "recoverable": true
  }
}

Requirements

• Python 3.10 or newer.
• A local MCP-compatible client.
• pyserial when using serial log capture.
• Local build, flash, or reset commands configured per device.

Installation

Clone the repository:

git clone https://github.com/Alooswr/firmware-mcp-server.git
cd firmware-mcp-server

Create a virtual environment:

python -m venv .venv

Activate it on Windows:

.venv\Scripts\activate

Activate it on Linux or macOS:

source .venv/bin/activate

Install the project in editable mode:

python -m pip install -e .

You can also install dependencies directly:

python -m pip install -r requirements.txt

Device Configuration

The default device config path is:

./config/devices.json

Create a local config from the example:

cp config/devices.example.json config/devices.json

On Windows Command Prompt:

copy config\devices.example.json config\devices.json

config/devices.json is intentionally ignored by git because it commonly contains local paths, serial ports, and private build commands.

You can override the config path with FIRMWARE_MCP_DEVICES_CONFIG.

Linux or macOS:

export FIRMWARE_MCP_DEVICES_CONFIG=/path/to/devices.json

Windows Command Prompt:

set FIRMWARE_MCP_DEVICES_CONFIG=C:\path\to\devices.json

Device entry shape:

{
  "device_id": "demo",
  "build": {
    "command": ["make"],
    "cwd": "/path/to/firmware/project"
  },
  "flash": {
    "command": ["make", "flash"],
    "cwd": "/path/to/firmware/project"
  },
  "reset": {
    "command": ["python", "scripts/reset.py"],
    "cwd": "/path/to/firmware/project"
  },
  "serial": {
    "port": "COM3",
    "baudrate": 115200,
    "timeout_ms": 3000
  }
}

Notes:

• device_id must be unique.
• build, flash, and serial are required.
• reset is optional.
• cwd is optional.
• command must be a non-empty array of strings.
• Commands are executed directly and are not interpreted by a shell.

MCP Client Configuration

Example client configuration when running from a cloned repository:

{
  "mcpServers": {
    "firmware": {
      "command": "python",
      "args": ["-m", "firmware_mcp_server"],
      "cwd": "/absolute/path/to/firmware-mcp-server"
    }
  }
}

Example with an explicit device config:

{
  "mcpServers": {
    "firmware": {
      "command": "python",
      "args": ["-m", "firmware_mcp_server"],
      "cwd": "/absolute/path/to/firmware-mcp-server",
      "env": {
        "FIRMWARE_MCP_DEVICES_CONFIG": "/absolute/path/to/devices.json"
      }
    }
  }
}

Run Locally

From the project root:

python -m firmware_mcp_server

The process uses stdio for MCP transport. Regular runtime traces are written to stderr as compact JSON log events.

Diagnostics

The runtime keeps an in-memory diagnostic timeline that combines tool execution traces and serial events. This internal layer does not add public MCP tools and does not change tool response formats.

Serial events are tagged with semantic states:

• BOOT
• CRASH
• HANG
• REBOOT_LOOP
• UNKNOWN

The deterministic classifier can return failure types such as:

• BUILD_FAILED
• FLASH_FAILED
• RESET_FAILED
• CRASH_AFTER_FLASH
• REBOOT_LOOP
• NO_BOOT
• UNKNOWN

Execution trace example:

{
  "event": "tool_execution_trace",
  "tool_name": "build_firmware",
  "device_id": "demo",
  "start_time": "2026-01-01T00:00:00.000Z",
  "end_time": "2026-01-01T00:00:02.000Z",
  "status": "ok"
}

Serial trace example:

{
  "event": "serial_log_line",
  "source": "serial",
  "device_id": "demo",
  "port": "COM3",
  "timestamp": "2026-01-01T00:00:00.000Z",
  "line": "boot",
  "state": "BOOT"
}

Development

Install development dependencies:

python -m pip install -e .

Run tests:

python -m unittest discover -s tests

Check ignored local files:

git status --ignored --short

Security Model

This server runs local commands from your device configuration. Treat devices.json as trusted local configuration and review commands before using them with an MCP client.

Important defaults:

• No HTTP listener is started.
• Commands are executed without shell=True.
• Device-local configuration is excluded from git by default.
• stdout is reserved for MCP protocol traffic.
• logs and traces are emitted to stderr.

See SECURITY.md for vulnerability reporting and operational guidance.

Contributing

Contributions are welcome. Please read CONTRIBUTING.md before opening a pull request.

License

This project is licensed under the MIT License.

Image assets are documented separately in ASSETS.md.