NemoClaw × Arduino Robot Arm

A safety-first reference project that lets a NemoClaw/OpenClaw agent control a four-servo Arduino robot arm through a narrow, auditable host bridge.

Status: prototype. NemoClaw itself is currently alpha software. Always test in mock mode first and keep a physical emergency stop within reach.

Architecture

User → NemoClaw sandbox → OpenClaw skill → HTTP allowlist → host bridge
                                                        ↓
                                               validation + rate limit
                                                        ↓
                                               USB serial → Arduino → servos

NemoClaw does not directly access USB. The bridge stays on the host and exposes only five commands: arm, disarm, move, home, and stop. Movement is blocked until explicitly armed, joint angles are bounded twice (host and firmware), and mock mode is the default.

What this project demonstrates

• A narrow, auditable agent-to-hardware interface rather than unrestricted serial access.
• Defense in depth across agent skill, host validation, firmware limits, interlock, and watchdog.
• A mock-first development path that can be tested without connecting physical hardware.
• A practical bridge from NVIDIA agent workflows toward ROS 2 / Isaac Sim sim-to-real validation.

Repository layout

.
├── arm_bridge/          # Validation, rate limiting, HTTP bridge, and CLI
├── firmware/            # Robot controller and calibration sketches
├── openclaw-skill/      # Narrow agent-facing commands
├── docs/                # Wiring and first-motion safety checklist
├── tests/               # Mock-mode behavioral tests
└── pyproject.toml        # Package metadata and command entry points

Hardware

• Arduino Uno/Nano-compatible board
• 4-axis hobby servo arm (base, shoulder, elbow, gripper)
• External regulated 5–6 V servo power supply
• Common ground between the servo supply and Arduino
• Physical emergency-stop/power-cut switch (strongly recommended)

Default signal pins are D3, D5, D6, and D9. Do not power multiple servos from the Arduino 5 V pin. Adjust pins and mechanical limits in firmware/robot_arm/robot_arm.ino for your hardware.

Follow the hardware setup and first-motion checklist before connecting servo power. It includes the wiring table, calibration sketch, normally-closed interlock, watchdog, and staged first-motion procedure.

1. Try it safely in mock mode

python3 -m venv .venv
source .venv/bin/activate
pip install -e '.[dev]'
arm-bridge

In a second terminal:

armctl arm
armctl move --base 120 --shoulder 80 --elbow 100 --gripper 60
armctl home
armctl disarm

2. Connect the Arduino

1. Install the ArduinoJson library in Arduino IDE.
2. Upload firmware/robot_arm/robot_arm.ino.
3. Find the serial port (/dev/ttyACM0 on many Linux systems or /dev/cu.usbmodem* on macOS).
4. Start the real bridge with an authentication token:

export ARM_BRIDGE_TOKEN='replace-with-a-long-random-value'
arm-bridge --serial /dev/ttyACM0

Keep the bridge bound to 127.0.0.1. If NemoClaw runs in a VM/container, expose it only through the OpenShell network policy—never directly to your LAN or the internet.

3. Add the OpenClaw skill

Copy openclaw-skill into the OpenClaw workspace’s skills directory. Make the helper executable and set the bridge URL/token through the sandbox’s approved secret/environment mechanism:

chmod +x openclaw-skill/scripts/armctl

Allow only the bridge endpoint in the NemoClaw/OpenShell network policy. The exact policy commands can change while NemoClaw is in alpha, so follow the version-matched NemoClaw network-policy documentation.

Example request to the agent:

Move the robot arm base to 120°, shoulder to 80°, elbow to 100°, and keep the gripper at 60°. Ask me to confirm the workspace is clear before moving.

Direct API

curl -X POST http://127.0.0.1:8765/command \
  -H 'Content-Type: application/json' \
  -H "Authorization: Bearer $ARM_BRIDGE_TOKEN" \
  -d '{"command":"move","joints":{"base":120},"duration_ms":800}'

Safety model

• Safe mock mode by default; serial access must be explicitly enabled.
• Explicit arming before movement and automatic disarm after stop.
• Joint allowlist, angle bounds, payload limit, and command rate limiting.
• Firmware repeats joint-bound checks; smooth interpolation reduces sudden moves.
• A D7 hardware interlock and five-second firmware watchdog detach servo outputs.
• Host-only bind by default and optional bearer-token authentication.

This is not safety-certified. Add hardware limit switches, current sensing, a watchdog, collision detection, and a real emergency stop before operating near people or valuable equipment.

Development

python -m pytest

Roadmap

• Add camera-based object selection and human confirmation.
• Add named, reviewed motion recipes instead of free-form joint commands.
• Add ROS 2 / Isaac Sim adapter for simulation before physical execution.
• Add telemetry, timeouts, and hardware watchdog support.

References

• NVIDIA NemoClaw
• NemoClaw documentation

License

MIT