CAN bus connection options

orel-20
uavcan

#1

On Titan Elite’s website it is recommended to daisychain multiple orel 20’s together and directly connect them to the CAN port on the Pixhawk flight controller. On our aircraft, we are utilizing a Pixhawk 4 flight controller and a UAVcan databus. We would like to be able to directly connect the Orel 20 ESCs ( we have 8 motors, and therefore 8 ESC’s) to the CANbus each as individual nodes (with the pixhawk being an individaul node as well) as opposed to daisychaining them and directly connecting to the Pixhawk 4 as is recommended. Is this possible?


(Pavel Kirienko) #2

CAN bus is, well, a bus, all nodes are able to directly communicate with each other without the need to rely on routing or retransmission of any kind. The following example image taken from the ArduPilot website should clarify things:

If this doesn’t answer your question, please explain what are you trying to achieve here by switching to the star topology.


#3

Sorry if I wasn’t as clear as I could have been with my initial inquiry. There are many other components on the aircraft that all connect via a CAN transceiver with a drop line to a main CAN bus line (a shielded twisted pair {STP} length of wire). However this is not how it is recommended to wire the CAN bus according to PX4 under the ‘wiring’ section nor according to Titan Elite’s image for wiring. According to these two sources, instead of wiring the ESC’s to a central CAN bus wire using drop lines, a ‘daisy-chain’ method is used to directly connect the components without drop lines from a main CAN bus wire. Since there are other non-Zubax components where a drop line from the main STP is being utilized, I am curious if a successful connection can be made from the Orel 20 ESC to a central CAN bus line using drops, or if I must daisy chain the ESC’s directly together. I would attach an image however I am not allowed to upload documents since I am a new user.


(Pavel Kirienko) #4

Thank you for the clarification, I now understand the question. You are asking whether you can use T-connectors; the answer is yes, you can, as long as you ensure that the stub length does not exceed the permitted limits. In this case, you should connect the drop line to either of the CAN connectors on your device, and leave the other connector empty (connected to nothing). Internally they are just electrically paralleled with no logic of any sort whatsoever.


#5

Great news. Thank you for your prompt replies, they’ve been very helpful.