A device on the CAN bus stops arming

What ArduPilot says:

• PreArm: DroneCAN: …
• PreArm: PiccoloCAN not enabled
• PreArm: PiccoloCAN: …
• PreArm: Same rfnd on different CAN ports

CAN is the two-wire bus that DroneCAN GPS units, compasses, ESCs and rangefinders share. “DroneCAN: …” carries a reason from the node list ArduPilot keeps: “Duplicate Node” means two devices claim one node number, or a device was replaced by another with the same number; “Node N unhealthy” means a device reports itself faulty. “Same rfnd on different CAN ports” means the two CAN drivers are set to the same rangefinder protocol. “PiccoloCAN …” concerns Piccolo CAN ESCs and servos.

What to do, most likely first

1. A DroneCAN device was swapped for another: ArduPilot remembers which hardware had each node number.

   CheckThe message is “Duplicate Node …” and it began after you changed a GPS, compass or ESC.

   FixSet bit 0 (ClearDNADatabase) of CAN_D1_UC_OPTION and reboot: the list is built again, and the bit clears itself.

2. A device on the bus is unhealthy: no power, still starting, or really faulty.

   CheckThe number in “Node N unhealthy” is the device's node number; the ground station's DroneCAN screen lists the nodes by number and name.

   FixCheck its power and connector. If it stays unhealthy, update its firmware or replace it.

3. Both CAN ports are set to the same rangefinder protocol, or to PiccoloCAN without Piccolo hardware.

   FixGive each CAN driver the protocol of what is really on it: CAN_D1_PROTOCOL 1 is DroneCAN, 0 is none. Reboot.

Parameters to look at

Where to do it:Board & Wiring Planner