nff 0.2.12

Claude Code IoT Bridge — connect Claude to hardware via USB

nff — Claude Code IoT Bridge

nff connects Claude Code to embedded hardware over USB — or to simulated hardware via Wokwi — with no real board required. It exposes your board as a set of MCP tools so Claude can autonomously write firmware, compile it, upload it, read serial output, and debug, all from a single conversation.

you: "Make the LED blink every 200 ms and print the state to serial"
Claude: [writes sketch] → [compiles] → [uploads to ESP32] → [reads serial] → done

you: "Simulate a servo controlled by a button, show me the circuit"
Claude: [writes sketch] → [updates diagram.json] → [nff flash --sim] → [nff wokwi run --gui] → VS Code opens with live animated circuit

Supported boards (v1): Arduino Uno · Mega · Nano · Leonardo · ESP32 (CP210x / CH340) · ESP8266 (FTDI)

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Demo

Wokwi Simulation

Real Hardware

Quickstart

1. Install

pip install nff

esptool is bundled — no separate install needed.

2. Install external tools

# wokwi-cli (required for simulation only)
# → https://github.com/wokwi/wokwi-cli/releases
# Get a free CI token at https://wokwi.com/dashboard/ci

# Board cores (install the ones you need)
arduino-cli core install esp32:esp32
arduino-cli core install arduino:avr
arduino-cli core install esp8266:esp8266

arduino-cli is auto-installed by nff init if it is not already on your PATH. You can also install it manually from https://arduino.github.io/arduino-cli.

3. Real hardware — plug in your board and run init

nff init

This single command does everything:

• Detects your board by USB vendor/product ID
• Writes ~/.nff/config.json and a CLAUDE.md in the current directory
• Registers the nff MCP server (claude mcp add nff nff mcp)
• Installs the /nff and /wokwi-diagram Claude Code skills globally

  ✓ Found: ESP32 (CP210x) on COM10
  ✓ Config written to ~/.nff/config.json
  ✓ CLAUDE.md written to ./CLAUDE.md
  ✓ Claude skills installed: /nff, /wokwi-diagram
  ✓ Registered with Claude Code CLI (claude mcp add nff nff mcp)
  ✓ Claude Desktop config updated

4. Simulation only — no board needed

nff wokwi init --board esp32:esp32:esp32 --token YOUR_TOKEN

Creates wokwi.toml and diagram.json in the current directory. Edit diagram.json to add components, then compile and simulate:

nff flash --sim sketches/my_sketch --board esp32:esp32:esp32
nff wokwi run --gui        # visual simulation in VS Code
nff wokwi run              # headless, serial output only

5. Verify everything works

nff doctor

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CLI Reference

Real hardware

Command	Description
nff init	Detect board, write config, register MCP server
nff flash <file>	Compile and upload a sketch or sketch directory
nff monitor	Stream serial output (Ctrl+C to exit, or --timeout SECONDS)
nff doctor	Check all dependencies and configuration
nff mcp	Start the MCP server (called automatically by Claude Code)

nff flash sketches/blink
nff flash sketches/blink --board esp32:esp32:esp32 --port COM3
nff flash sketches/blink --manual-reset    # for boards with broken auto-reset
nff monitor --port COM10 --baud 115200
nff monitor --port COM10 --baud 115200 --timeout 15   # stop after 15 seconds

Wokwi simulation

Command	Description
nff wokwi init	Scaffold wokwi.toml + diagram.json in current directory
nff flash --sim <file>	Compile sketch and run headless Wokwi simulation
nff wokwi run	Run simulation, stream serial output to terminal
nff wokwi run --gui	Open diagram.json in VS Code and auto-start visual simulation
nff wokwi run --serial-log FILE	Save serial output to file
nff wokwi run --timeout MS	Set simulation timeout (default 5000 ms)

nff wokwi init --board esp32:esp32:esp32
nff flash --sim sketches/servo_button --board esp32:esp32:esp32
nff wokwi run --gui
nff wokwi run --timeout 10000 --serial-log out.txt

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Visual Simulation with VS Code

Install the Wokwi VS Code extension to get an animated circuit view alongside a serial monitor panel — no browser required.

nff wokwi run --gui

This opens diagram.json as a new tab in your existing VS Code window and automatically triggers Wokwi: Start Simulator after 3 seconds. Click components (buttons, potentiometers, etc.) to interact with the running simulation.

Workflow:

Edit sketch  →  nff flash --sim  →  nff wokwi run --gui  →  click in VS Code
     ↑_____________________________|

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diagram.json — Circuit Schematic

The circuit lives in diagram.json next to wokwi.toml. nff wokwi init generates a minimal single-MCU stub; add components and wiring by hand or ask Claude.

Always include the serial monitor wires:

["esp:TX0", "$serialMonitor:RX", "", []],
["esp:RX0", "$serialMonitor:TX", "", []]

Common components:

{ "type": "wokwi-led",        "id": "led1", "attrs": { "color": "red" } }
{ "type": "wokwi-pushbutton", "id": "btn1", "attrs": { "color": "blue" } }
{ "type": "wokwi-servo",      "id": "srv1", "attrs": { "minAngle": "-90", "maxAngle": "90" } }
{ "type": "wokwi-resistor",   "id": "r1",   "attrs": { "value": "220" } }

ESP32 DevKit V1 pins: esp:D<gpio> · esp:GND.1 · esp:GND.2 · esp:3V3 · esp:VIN · esp:TX0 · esp:RX0

Pushbutton wiring: one side to GPIO (btn1:1.l), other side to GND (btn1:2.l). Use INPUT_PULLUP in the sketch.

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ESP32 Servo — No Library Required

Use the built-in LEDC peripheral instead of ESP32Servo. Wokwi maps its full servo range to 500 µs – 2500 µs pulses.

With 50 Hz / 16-bit resolution (period = 20 000 µs):

Angle	Pulse	Duty
−90° (min)	500 µs	1638
0° (center)	1500 µs	4915
+90° (max)	2500 µs	8192

ledcAttach(SERVO_PIN, 50, 16);     // ESP32 Arduino core 3.x API
ledcWrite(SERVO_PIN, 4915);        // move to center

Set "minAngle": "-90", "maxAngle": "90" in diagram.json for correct visual mapping.

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MCP Tools (what Claude can call)

Once registered, Claude Code has access to these tools:

Tool	What it does
list_devices()	List all connected USB boards
flash(code, board?, port?)	Write, compile, and upload a sketch
serial_read(duration_ms?, port?, baud?)	Capture serial output for N ms
serial_write(data, port?, baud?)	Send a string to the device
reset_device(port?)	Toggle DTR to hardware-reset the board
get_device_info(port?)	Return port, board name, FQBN, baud rate
wokwi_flash(code, board?, timeout_ms?)	Compile and simulate a sketch via Wokwi
wokwi_serial_read(code, board?, duration_ms?)	Compile, simulate, return serial output
wokwi_get_diagram(board)	Return a minimal diagram.json stub to extend

All tools fall back to the default device in ~/.nff/config.json when port and board are omitted.

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Config File

~/.nff/config.json, written by nff init and nff wokwi init, editable by hand:

{
  "version": "1",
  "default_device": {
    "port": "COM10",
    "board": "ESP32 (CP210x)",
    "fqbn": "esp32:esp32:esp32",
    "baud": 115200
  },
  "wokwi": {
    "api_token": "YOUR_TOKEN",
    "default_timeout_ms": 5000,
    "diagram_path": null
  }
}

The Wokwi token can also be set via the WOKWI_CLI_TOKEN environment variable (takes precedence over config).

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Supported Boards

Board	Vendor ID	Product ID	FQBN
Arduino Uno	2341	0043	arduino:avr:uno
Arduino Mega 2560	2341	0010	arduino:avr:mega
Arduino Leonardo	2341	0036	arduino:avr:leonardo
Arduino Nano	2341	0058	arduino:avr:nano
ESP32 (CP210x)	10c4	ea60	esp32:esp32:esp32
ESP32 (CH340)	1a86	7523	esp32:esp32:esp32
ESP8266 (FTDI)	0403	6001	esp8266:esp8266:generic

Board not listed? Open a PR — adding one is two lines of code.

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Claude Code Skills

nff ships two Claude Code skills that are automatically installed to ~/.claude/commands/ when you run nff init, making them available globally in every Claude Code session.

Skill	When to use
/nff	Full pipeline reference — hardware and simulation workflows, sketch-first rules, servo calibration, debugging checklist
/wokwi-diagram	diagram.json authoring reference — component types, pin names, wiring patterns for LEDs, buttons, servos, sensors

Type the skill name in any Claude Code prompt to load the reference into context:

/nff
/wokwi-diagram

The skill files are also available in the repository at .claude/commands/ for project-level use, and are bundled inside the nff package at nff/skills/ so they ship with every pip install nff.

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Repository Structure

nff/
├── nff/
│   ├── cli.py              # Click entry point — routes subcommands
│   ├── mcp_server.py       # MCP server — registers all tools for Claude
│   ├── config.py           # Read/write ~/.nff/config.json
│   ├── commands/
│   │   ├── init.py         # nff init
│   │   ├── flash.py        # nff flash [--sim]
│   │   ├── monitor.py      # nff monitor
│   │   ├── doctor.py       # nff doctor
│   │   └── wokwi.py        # nff wokwi init / run [--gui]
│   └── tools/
│       ├── boards.py       # USB vendor ID detection
│       ├── serial.py       # pyserial read/write/stream
│       ├── toolchain.py    # arduino-cli subprocess wrappers
│       └── wokwi.py        # WokwiRunner, generate_diagram, write_wokwi_toml
├── sketches/
│   ├── blink_esp32/        # LED blink example
│   └── servo_button/       # Servo + button example (LEDC, no library)
├── diagram.json            # Wokwi circuit schematic
├── wokwi.toml              # Wokwi project config (points to compiled ELF)
├── .claude/
│   └── commands/
│       └── nff.md          # /nff Claude Code skill
├── tests/
├── pyproject.toml
└── CONTRIBUTING.md

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Linux: Serial Port Permissions

sudo usermod -aG dialout $USER
# then log out and back in

nff doctor detects this and prints the fix if your port is inaccessible.

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License

MIT — see LICENSE.
Copyright (c) 2026 Gauthier Lechevalier