CAN & DroneCAN

ArduConfigurator talks to the CAN bus two ways. The everyday CAN tab manages DroneCAN nodes during setup; the DroneCAN Inspector is an expert-only, Mission Planner-style surface for deeper node management — node health, parameters, restart, and firmware update over CAN. Both reach the bus the same way: they ask the autopilot to forward a CAN bus over the live MAVLink link, so you never have to switch the flight controller into a dedicated SLCAN mode.

How the bus is reached

Rather than SLCAN, the configurator uses MAVLink CAN forwarding. It sends MAV_CMD_CAN_FORWARD to the autopilot, which then tunnels raw CAN_FRAME messages for the chosen bus (CAN1 or CAN2) over the same MAVLink connection you are already using. The advantage is that normal telemetry keeps flowing on the link — you do not drop the vehicle connection to inspect the bus.

Note

ArduPilot stops forwarding CAN frames roughly 5 seconds after the last MAV_CMD_CAN_FORWARD request. The configurator re-arms forwarding well inside that window (about every 2 s) for as long as a bus is active, so the stream does not lapse mid-session. If a node goes quiet, it is almost always the bus itself, not the tunnel.

Outbound DroneCAN service calls (parameter reads/writes, restart, firmware file-serving) are sent as extended CAN_FRAME messages on the same tunnel. Because the tunnel is best-effort, the app retries lost requests with bounded budgets and watchdogs rather than assuming a single send arrived.

DroneCAN Inspector

The DroneCAN Inspector is an Expert-mode tool — enable Expert mode to reveal it (alongside the Logs & Inspectors MAVLink Inspector). Pick CAN1 or CAN2 and Start the bus; the inspector forwards that bus and builds a live node inventory.

Each node is discovered from its periodic uavcan.protocol.NodeStatus broadcasts and named by an active uavcan.protocol.GetNodeInfo poll. The node table shows, per node:

  • Node id and name (e.g. org.ardupilot.Here4AP)

  • Health — ok / warning / error / critical

  • Mode — operational / initialization / maintenance / software_update / offline

  • Uptime and last-seen age

Bus stats (frames/s and node count, with an unhealthy-node count) sit above the table. Expanding a node reveals its hardware/software version, the unique id, and the per-node actions below.

Note

The inspector also surfaces ESC telemetry (uavcan.equipment.esc.Status) per ESC index — RPM, voltage, current, temperature, power, and error count. This is observe-only.

Node parameters

Open the Parameters section under an expanded node to walk its parameter table over uavcan.protocol.param.GetSet (the walk is collapsed by default because it triggers a bus read; opening it pulls the values, and Re-fetch re-walks from the start).

Edit a value and use Apply & Save. DroneCAN GetSet writes are RAM-only, so the app follows the writes with a uavcan.protocol.param.ExecuteOpcode SAVE once every write is acknowledged — without that SAVE, changes revert on the node’s next power cycle. After a successful save the node’s parameters are re-fetched automatically so the grid reflects what is actually stored.

Note

AP_Periph nodes usually strip parameter metadata, so a node reports a raw value with no label, range, or enum. The configurator enriches the grid by matching each parameter by name against the curated flight-controller catalog, filling in a friendly label, range hint, enum value labels, and a description. This is best-effort — a peripheral’s range or enum may differ from the same-named flight-controller parameter, and node-reported values always win when present.

Restart node

Restart node sends uavcan.protocol.RestartNode (behind a confirm step). The node reboots and drops off the bus briefly, then reappears.

Firmware update over CAN

The inspector can flash AP_Periph node firmware over the CAN tunnel, with the GCS acting as the file server. It sends uavcan.protocol.file.BeginFirmwareUpdate and then answers the node’s file.Read requests with chunks of the selected image until the node has read the whole file and reboots into it. Only one update runs at a time, and every other action on the bus is locked while it runs.

Select an AP_Periph.bin image, acknowledge the brick-risk confirmation, and Update firmware. For an ArduPilot org.ardupilot.<board> node the UI deep-links the matching AP_Periph.bin on firmware.ardupilot.org so you can download the right build in one click.

Warning

Flashing the wrong or corrupt image can permanently disable a node. Keep the bus connected and powered for the whole transfer. A firmware update can also reset or corrupt a node’s parameters — once the node is back, re-fetch its parameters and re-check your settings (LED, GPS, compass, …) before flying.

Note

Online firmware lookup is desktop-only. A browser cannot fetch the ArduPilot firmware server directly (no CORS), so the browser build degrades to the manual-download path. PX4 and other vendor CAN devices are also supported on the bus, but they get firmware from their own vendor — the AP_Periph build matching only applies to ArduPilot nodes.

The normal CAN tab

The everyday CAN tab is a separate surface from the Inspector. It uses the same MAV_CMD_CAN_FORWARD tunnel and the same node-discovery and parameter read/write/save plumbing, but is aimed at routine DroneCAN node setup rather than the full expert toolkit (firmware update and ESC telemetry live in the Inspector). It is available without Expert mode.

Tip

“Enable the CAN bus?” A common trap is to set a peripheral’s driver to DroneCAN and then find nothing on the bus, because the CAN interface itself was never turned on. There is no error — the node is powered, on the wire, and completely invisible. The triggers the app watches for are GPS_TYPE or GPS_TYPE2 = 9 / 22 / 23 (DroneCAN, and the two moving-baseline variants), BATT_MONITOR or BATT2_MONITOR = 8, and FLOW_TYPE = 6.

When one of those is selected but CAN bus 1 is not enabled for DroneCAN, a one-click Enable CAN bus & reboot prompt writes CAN_P1_DRIVER = 1 (bind physical interface 1 to virtual driver 1) and CAN_D1_PROTOCOL = 1 (run DroneCAN on that driver) after an automatic backup. Both are reboot-required; nodes appear after the reboot. The prompt shows on the CAN tab for any of those triggers, and on the optical-flow section of the Peripherals surface for the FLOW_TYPE trigger — see Peripherals & Gimbal.

See also Parameters (Expert) for editing flight-controller parameters and Logs & Inspectors for the live MAVLink stream.

For DroneCAN concepts, node configuration, and bus wiring on the firmware side, the ArduPilot wiki is canonical: DroneCAN setup.