Re: CAN Inspector: a CAN node to sample the CAN bus waveforms

Hi John,

Thanks for your comments.

> The first question I'd ask would be who gets this information and how do
> they get it?

My CAN bus connects to a Linux computer that has an Iridium modem, so this gives me contact from the outside world.

> and there's no way to add functionality to it in the form of
> an scope module?  

Well, I could add a scope module. Maybe that is the smart thing to do. I just like the idea of a simple CAN node to do the job. And our CAN nodes (based on the AT90CAN128) survive cold-soaking to -80C.

> The problem you face is if your CAN bus is crippled due to a physical issue
> any scope device that is on the same CAN bus becomes useless.  

Yes, that's true, but so far all my issues have been loss of redundancy, not outright failure.

> Perhaps you could add some details as to how you would report the bus
> information?

After grabbing 1 kB of bus waveform, the CAN node could be instructed to download it across the CAN bus 8 bytes at a time. The CAN node would need some moderately clever software, e.g., perhaps repeatedly grabbing 1 kB samples until one of them happens to contain the leading/trailing edge of a bit. I'm also thinking of incorporating a high-speed pulse generator to make a "poor man's TDR" (or perhaps it should be called a "crazy man's TDR" if this project gets out of hand!).

Regards,
Michael
-- 
Professor Michael Ashley                   Department of Astrophysics
University of New South Wales       http://www.phys.unsw.edu.au/~mcba
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