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Old 11-30-2015, 05:08 PM   #2412 (permalink)
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With all the work you guys are doing with the data, I started thinking a bit about how to do this with the CAN bus.

It's really nice that you can stream data using standard serial data; that could be very useful in the future; not only for debugging.

Actually, the CAN bus really isn't a big deal; is mostly a communication protocol. There a quite a few requirements for meeting the protocol - actually more than the hardware requirements...

I think it would be nice to use the CAN/OBDII protocol for the communication - that way external devices could be used for monitoring, etc.

The main part of the protocol is pretty easy - there are two versions. The "standard" frame uses an 11 bit identifier and the "extended" frame uses a 29 bit identifier. Both frames can transmit up to 8 bytes of data.

All the other stuff, including bits that communicate message priority, a CRC check, etc are the same. The bus speed is somewhat adjustable, with the main tradeoff being noise immunity and processor time for high bus speeds.

The main problem is that outside the government regulated indentifiers, there is very little information about the identifier. Since the protocol was originally design for pollution control, there is nothing I can find about EV stuff.

For example, EVTV has those nice Andromeda interfaces that display a lot of useful EV stuff, all transmitted by CAN. However I can't find anything about which indentifiers they use.

It sure would be nice to come up with a set of identifiers that would be useful for EV's and readable by any CAN bus / OBDII scanner.


- E*clipse
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