Since CAN Bus is a differential signalling system, what is the significance of GND/COM signal? Can I get by without it?
I've got a very simple 2-node system that has some weird happenings going on. (see here for that issue, if you're interested) The two nodes are my device and a USB-CAN monitor; both have 120ohm termination resistors, and the wire run between them is <1m.
I just remembered that in my earlier tests I only had the CAN_H and CAN_L signals connected between the nodes; I did not have anything connecting the CAN_COM of my device to the ground pin on the USB-CAN monitor.
A (the?) point of differential signaling is to be much less (not?) effected by common mode noise. So by not having the ground connected, I would guess we lose the absolute reference for CAN_H and CAN_L... but does that make a difference?