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0 pointsSV_BubbleTime5y ago0 comments

No, I was not thinking RJ485 where termination is optional.

You are forgetting that CAN can work at short distances without being a differential bus at all.

I mention this where I wrote “no transceiver AND no termination”.

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zootboy5y ago· 2 in thread

In that case, it's not really CAN, it's more like CAN-tranceiver-control-signals. That may work, but would realistically be limited to only two devices, at which point it probably makes more sense to just use a protocol that's meant for short point-to-point links, like U[S]ART or SPI.

SV_BubbleTimeOP5y ago

I think a better way to describe it that it’s CAN all the way up until the PHY. It’s still CAN protocol, you still need CAN modules, and really, nothing looks different at all to them.

You just lose out on the differential pair... but even that isn’t required when you look at fault tolerance CAN in single wire mode, or single wire CAN PHY transceiver options, as to the original point about termination, I can’t remember if Single Wire CAN is terminated in a loop or pulled up or down, but I promise it’s not 120ohm termination like differential CAN is.

Imo, safer to say that CAN is a protocol that can take many physical forms, and one of them is direct A to B modules with no termination.

a9h74j5y ago

Yes. You could do all-point-to-point CAN by or-ing all of the CAN-TX logic-level outputs, perhaps in an inverted tree, and then fanning out the global OR result to all CAN-TX logic-level inputs. Or, at short distances, just use wired-or at logic levels.

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