#uavcan

Troubleshooting CAN bus for RC: MAVLink, UAVCAN sensors and servo buses.

CAN bus is becoming a popular backbone for modern RC models because it reduces wiring clutter and gives robust communication between flight controllers, ESCs and sensors. This guide focuses on practical troubleshooting for hobbyists who use MAVLink and UAVCAN devices, and for those integrating servo buses into a CAN environment. The goal is to help you quickly identify the usual faults and restore reliable operation without needing specialist support.

Start with the usual suspects when a CAN system misbehaves: physical wiring faults, poor connectors, incorrect termination, and power problems cause the majority of faults. Symptoms you will see are intermittent device lists, missing heartbeats, corrupted telemetry, and bus errors reported by your flight controller. Look for obvious damage to cables and pins, loose crimps, and moisture at connectors before diving into software or firmware changes.

MAVLink over CAN introduces extra complexity because you are mapping MAVLink messages on top of the CAN transport layer. If MAVLink messages stop flowing check that your flight controller firmware supports MAVLink on CAN, that node IDs and component IDs are configured correctly, and that there are no rate floods from high-frequency streams. Use your ground station to monitor heartbeats and system status and consider temporarily reducing message rates to isolate a noisy node. Remember that CAN operates at fixed bit rates, so make sure every device on the bus is configured to the same bitrate.

UAVCAN sensors bring advantages in plug-and-play telemetry but can confuse troubleshooting when nodes share IDs or run incompatible protocol versions. Confirm whether your devices use UAVCAN v0 or v1 (Cyphal) as they are not directly compatible, and inspect the node ID allocation to avoid conflicts. Common sensor problems are power rail droop during startup, incorrect node configuration or failed calibration steps. Tools such as a CAN analyser, Yakut or manufacturer utilities help enumerate nodes and view health and parameter messages so you can pinpoint failing or misconfigured sensors.

Wiring reliability and servo power are often the weak link in RC CAN setups, so adopt best practice wiring now to avoid troubleshooting later. Use a twisted pair for CAN high/low with a single ground reference, keep stubs short and avoid star topologies, fit proper 120 ohm termination at each end of the main trunk and earth shields at one end only. Separate the high-current servo power rails from the CAN signal pair and provide local decoupling capacitors at power-hungry servos and ESCs. If you need wiring diagrams or parts lists, see my blog at WatDaFeck for practical examples and photos.

When sensors, MAVLink bridges or servo buses stop working follow a systematic isolation workflow to save time and parts. Power down and isolate sections, reintroduce a single node on a known-good cable, check voltages and grounds with a multimeter, swap short cables, then add nodes one at a time while watching the node list. Use a CAN sniffer or logic analyser to check for bus errors and to view arbitration and error frames, and an oscilloscope to inspect signal integrity and ringing on long runs.

Check physical layer first: continuity, termination and correct pins for CAN H/L.

Verify power rails: voltage under load and common ground between devices.

Confirm protocol versions and node IDs for UAVCAN components.

Monitor heartbeats and node lists in your ground station for MAVLink visibility.

Swap components and cables to isolate a faulty node or connector.

Finally, keep firmware up to date and maintain a log of changes so you can roll back when a new release causes issues, and consider adding simple redundancy such as dual power feeds or protected fuses for critical servo circuits. With a methodical approach to the physical layer, protocol settings and systematic isolation you will resolve most CAN bus faults quickly and get your aircraft or vehicle back in the air or on the water.

CAN bus for RC: a beginner's guide to wiring, MAVLink, UAVCAN and servo buses.

CAN bus is a robust, multi-drop communications system originally developed for automotive use and now finding its way into RC models and drones due to its noise immunity and simple wiring requirements.

For hobbyists, understanding how CAN interacts with flight software and telemetry is important, because MAVLink is the messaging language most flight controllers use for commands and telemetry and can be bridged to CAN systems when required.

UAVCAN is a higher-level protocol designed specifically for UAV components and sensors that runs on a CAN physical layer, providing plug-and-play discovery, node IDs and structured data for devices such as GPS modules, LiDAR and current sensors.

Wiring reliability is the single biggest practical concern when you move to CAN in an RC model, so use a proper twisted-pair for the CAN_H and CAN_L signals, keep run lengths reasonable, fit 120 ohm termination resistors at each end of the bus and avoid star topologies by daisy-chaining nodes in sequence.

Servo buses driven by CAN or other serial bus protocols remove the need for many PWM wires, allow servo feedback and diagnostics on the same cable and simplify wiring for complex models, but remember to check each device's power requirements and to keep power distribution separate from the data pair whenever possible.

Practical starter tips include powering up and testing one device at a time, using quality connectors and ferrules, checking for firmware compatibility between flight controller and sensor nodes, and keeping a small CAN sniffer or logic analyser handy for troubleshooting, and if you want build logs and step-by-step wiring diagrams you can read more on my blog at WatDaFeck.