>This is very hard if the bus use one of the
>"non-standard" data rates.

It wouldn't surprise me knowing the way this particular manufacturer does
things in a non-standard way.

>But if it does, one of (10,15,20,50,100,125,250,
>500,800,1000 kbps) , its easy. Just set the CAN
>circuits in to listen only mode and check if you
>see andy frames on each of the bitrates in turn.
>This is how most do it.

I was figuring this might have to be how I do it.

>For a given time quanta etc you could probably
>come up with something else also but that would
>defintly be a tiresome and very lengthy process.
>You can play with the different parameters wit
>this .intrepidcs.com/website/BitCindex.htm or
>some other bitcalculator.

http://www.intrepidcs.com/website/BitCindex.htm

Hey, that is a nice looking bit of software, and a host of other info about
CAN as well. Anyone else looking at doing CAN, I suspect this site is worth
looking at, from a 5 minute glance. They certainly seem to have put some
effort in to the calculator.

>If it's a one of use a DSO an look at one bit and you have it .

I am hoping this will be a "last resort" part. I am not sure how I can look
at "one bit" as the waveform is NRZ, which is why they do bit stuffing, to
guarantee a clocking edge for the receiving PLL to sync to. I am hoping that
the way the MChip parts work, even with an error in listen mode, it will
dump the receiver contents into the buffer so it may be possible to figure
out where a sync edge looks like it occurs, and so working from a "standard"
bit rate, zoom in on a non-standard one quicker. Least the diagrams in the
MCP2515 datasheet should help here - again to anyone looking at doing CAN
these are the best diagrams I have seen about the message format, and they
just don't put them in the 18F datasheets.

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