ODrive Pro Fully Isolated CAN

Support ODrive Pro Support
1

I am using 9 ODrive Pros where every 3 are powered by independent 48V batteries that do not share a ground. This is a distributed robotic system.

A single Raspberry Pi is used to communicate to the 9 ODrives via CANbus. The CAN interface is the PICAN2 which is not isolated. I am currently only using this with a single ODrive for developing the CAN interface software.

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The ODrive’s documentation on running fully isolated is lacking details. I know that I will need to remove two jumpers on each drive so that the ODrive Pros do not power their CAN transceivers from internal 12V power, or reference the transceiver ground to the internal 12V logic ground. In this case I can use a local isolated 12V power supply to power the CANbus transceiver on each ODrive.

In this configuration I should NOT need to connect the -48V to CAN ground. However - do I need to connect the 3 CAN grounds together? Or can I leave them floating from each other? Would a CAN isolator (rated for 1Mbps) be advisable between the Raspberry Pi and the CAN bus? Or an isolator between each panel?

I would like the ODrive Pro documentation to be updated to include wire-level drawings of each isolation method. This bullet is the only mention of fully isolated CAN:

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It fails to clarify that this means, by my interpretation, that the internal logic of the ODrive Pro will now be fed from the high voltage input, meaning you can only communicate with the ODrive Pro if the high voltage is present.

2

Hi Andrew! I believe we’re talking about this over email, is that an acceptable place or would you like to have the discussion here?

3

Is it possible to share the details regarding this question here, I’m working on can on odrive pro and would like to know more

4

Hi! The brief is just:

  • If you remove the 0-ohm resistor jumpers R96 and R97 on each ODrive, the CAN transceiver will be fully isolated from the battery GND.
  • This also loses you the ability to power the ODrive Pro via an external 12V auxiliary connection to maintain logic power while the main DC bus is switched off.
  • Nominally, the CAN transceiver is referenced to CAN GND but powered via a required external tie between DC- and CAN GND.
  • If you remove the jumpers (or order ODrive Pros customized, without them populated), then CAN will be fully isolated with respect to DC-, and you will require an external 12V supply on CAN_12V / CAN_GND.
  • Whether isolated or not, the CAN transceiver is referenced to CAN_GND, so you would require a ground reference. However, this is just a signal reference and not a power ground (current flow will be only a few mA).
  • For instance, if the Raspberry Pi uses an isolated CAN transceiver, then the entire CAN network could be isolated with respect to all battery grounds (assuming you’re using the isolated 48V/12V supplies and R96/R97 are desoldered/unpopulated).

Do you have any other questions yourself?