2010/8/20 roystonvasey <mikestocks@madasafish.com>



dtran11 wrote:
>
> I am currently trying to use a mcp2515 for CAN communication. I would like
> to run it at 1Mbps bitrate because I will be needing about 6000 can
> messages per second. After several testing, I have found it to be only
> stable (no missed frames) at 2000 can messages per second. I would like to
> know if any has had any experience with the mcp251x driver and what
> performances you saw?
>
> Thanks.
>

I've had the MCP2515 running quite happily with a CAN of 1Mbps. However at
high frame rates I've had dropped frames. The bottle neck was the SPI bus.
The MCP2515 SPI bus can run up to 10MHz. I've found the limiting factor to
be the speed of the level shifter. Your instability may be caused by the
level converter on the IRQ or CS lines.

Cheers Mike.
--
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dtran11 guess you are the same as dat who writes on http://www.bobandeileen.com/?p=479
If not take a look there or at http://old.nabble.com/MCP-2515-RX-problems-td29365471.html

Mike I'm a bit surprised if you were able to use 1Mbps unless there were a gap between each frame.
I'm running SPI @ 10Mbps and I loose frames @ 250Kbps with the patch (see link above)
Did you use an out of the box 2.6.34 or?

There is another thread here regarding SPI latency: http://old.nabble.com/Howto-get-lower-latency-on-the-SPI-bus-td29378861.html I still have to do a few test, but dtran11 if you have time you could try to test IRQ latency (ScottEllis did send a link to a project he used for that purpose, but I have not had the time to check it out yet)


Thanks
Benny