TRS jack for CANbus

[Rick Finsta]

Alright, rather than bringing the CANbus out the DB37 (since I have to pull a bunch of wiring out of the car to do so; I didn't make that harness as modular as I should have behind the dash) I was going to install a TRS (stereo 3.5mm) jack in the case. I was going to use:

Tip = High
Ring = Low
Sleeve = Ground

My original thought was this way I could ensure there was a shared ground between peripherals and the ECU but the more I think about it the more I wonder if I'm opening myself up to ground loop problems. Should I wire it this way, or should I wire it ignoring the Ring and just use Tip = High and Sleeve = Low? The other devices I've seen using mini stereo jacks have been using TRS but I don't really know details of the implementation. The most likely use of CANbus for me is going to be either a Microsquirt-based transmission controller if that makes a difference. I figured while I had the case open (upgrading to MS3) I would just install that as well.

[racingmini_mtl]

Just as a point of reference, the CAN-EGT uses a TRRS jack where the tip is 12V, the first ring is CANH, the second ring is CANL and the sleeve is ground. That way you can power the unit from the same cable as the CAN bus. And it has DIP switches to disconnect the 12V and ground from the jack so that you don't create unwanted loops if you don't power the unit from the CAN bus cable.

Jean

[Rick Finsta]

Thanks very much for the quick feedback! I'll think about that for sure. Looks like the Megaspartan runs into a screw terminal header so considering I will likely be using both when I go boosted I'm thinking I'll wire up a TRRS terminal.