CAN Bus dev board

[[email protected]]

Hi All,

I've been developing with the CCS can dev board and everything works great. Until I remove Node B from the board (or hold it in reset) now EX6 example on Node A can no longer talk to Node D.

There appears to be something in Node B can_init() that enables Node A to communicate with Node D correctly. Holding B in reset when restarting appears to break A to D communications. The can instructions are Tx'ed onto the bus but never acknowledged.

If any has any ideas they would be greatly appreciated

Thanks in advance

Greg

[newguy]

I don't have the CCS CAN development board but I may be able to offer some insight. CAN communications can be foiled by a faulty node if that node holds one or both of the CAN bus lines in the dominant state. Perhaps node B has pullups/downs on the lines that interface to the CAN transceiver?

[[email protected]]

Thanks .... But I have physically removed Node B including the tranciever and still have the same problem.

[newguy]

Well that has me stumped then. You'll have to wait for someone with that development board to weigh in. Sorry.


.....Wait. A & C are still on the board but all comms cease when node B is removed? Are you sure that nodes A & C still function properly when B is gone? That's the only thing I can think of - that for some reason one or both of the remaining nodes no longer functions which will also hang the CAN bus.

[[email protected]]

Thanks for your reply.
Let me clarify, the comms do do cease exactly Node A continually sends, I can see the data at Node D Rx but Node D doesn't respond.

Also note Node B can be held in reset after Node A has started and everything continues fine.

My speculation is Node D (a MCP25250) either is not "waking-up" or is configured incorrectly.
Leaving the question does node B 16F876 can_init() do something
differant to 18xxx8 can_init().

still confused ....