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urml-ardupilot-runtime

ArduPilot / MAVLink reference runtime for URML. Flies ArduCopter (a Pixhawk-class board running ArduPilot, or ArduCopter SITL) from a validated URML program over pymavlink. No ROS 2 dependency. This is the package RFC-0041 proposed; Copter ships first, Plane and Rover are follow-ups.

ArduCopterAdapter subclasses the PX4 reference adapter (urml-px4-runtime). The MAVLink command set is shared; what this package adds is the firmware behaviour ArduPilot needs around those commands and PX4 does not.

What ArduPilot needs that PX4 does not

Nothing in this package disables ARMING_CHECK or any pre-arm gate. On a bench with no GPS fix the autopilot refuses GUIDED or arming, and the adapter reports that refusal as the step's reason and stops. That refusal is the intended bench proof.

Method coverage

Install

pip install -e reference/ardupilot-runtime[ardupilot]

The extra installs pymavlink and pyserial. Without it the module imports but constructing the adapter raises a clear install hint.

Bring-up

Read-only probe. Sends no mode, arm, or motion command.

python -m urml_ardupilot_runtime.probe COM5

Prints the autopilot type, vehicle type, MAVLink system id, armed state, mode, firmware version, battery voltage, GPS fix, and any recent STATUSTEXT. A Pixhawk on USB is usually COM<n> on Windows and /dev/ttyACM0 on Linux; ArduCopter SITL is udp:127.0.0.1:14550.

Use

urml execute program.urml.yaml -m manifest.yaml --profile drone --no-policy \
    --adapter ardupilot --adapter-config ardupilot_adapter.yaml

A minimal ardupilot_adapter.yaml:

connection_url: "COM5"
baud: 115200

location_to_pose:          # local metres from the launch point
  bench_north: { north: 5.0, east: 0.0, alt: 3.0 }
  home:        { north: 0.0, east: 0.0, alt: 0.0 }

location_to_global:        # WGS84, wins over location_to_pose for the same name
  site_p1: { lat: 32.0853, lon: 34.7818, alt_agl: 100.0, look_at: { lat: 32.0850, lon: 34.7815 } }

camera:
  kind: digicam            # or `servo` with `channel`

output_lines:
  payload_latch: { kind: gripper, instance: 1 }
  winch:         { kind: winch, instance: 1, deliver_length_m: 15.0, rate_m_s: 0.5 }

location_to_global is written by tools/scripts/geocode_locations.py at configuration time. The runtime never geocodes and never touches the network.

From Python:

from urml_ardupilot_runtime import ArduCopterAdapter, load_ardupilot_config
from urml_ros2_runtime import URMLRuntime

with ArduCopterAdapter(load_ardupilot_config("ardupilot_adapter.yaml")) as adapter:
    runtime = URMLRuntime(adapter)
    result = runtime.execute(program, manifest, envelope, profiles=("drone",))

CompositeAdapter from the PX4 runtime accepts an ArduCopterAdapter as its flight backend unchanged.

Tests

Three tiers, mirroring the PX4 runtime:

• tests/test_arducopter_adapter.py: hermetic, a fake pymavlink is injected; runs everywhere.
• tests/integration/test_arducopter_live.py: gated on URML_ARDUPILOT_INTEGRATION=1; real pymavlink, no autopilot contacted.
• tests/integration/test_arducopter_bench.py: gated on URML_ARDUPILOT_BENCH=<port>; a real board, props off. Asserts the identity probe, a successful battery read through the runtime, and that a take-off is refused cleanly by the autopilot's own pre-arm checks.
• tests/integration/test_arducopter_sitl_e2e.py: gated on URML_ARDUPILOT_SITL=1; flies the drone/flight_only_positive conformance fixture against ArduCopter SITL.

Status

Bench link verified on hardware (Pixhawk, ArduCopter 4.6.3, USB). The SITL e2e (flight-only fixture plus both flight-test examples) is green against ArduCopter SITL built from Copter-4.6.3, run locally on 2026-08-29. No physical flight is claimed anywhere in this repository; see docs/demos/sentence-to-pixhawk.md for the bench runbook and the two flight-test runbooks that gate a field run on a green SITL pass.

License

Apache 2.0. The adapter talks to ArduPilot firmware (GPLv3) over MAVLink; it links pymavlink (LGPLv3) as a normal Python import and never links the firmware.