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Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?
From: |
Bruce D. Lightner |
Subject: |
Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus? |
Date: |
Sun, 25 Jul 2004 23:18:19 -0700 |
User-agent: |
Mozilla Thunderbird 0.5 (Windows/20040207) |
Reza Naima wrote:
In fact there are both SAE *and* ISO standards which apply to the OBD-II
automotive CAN-bus. They are in fact "available"...for a fee. However,
getting everthing you need is pretty expensive. (One of the ISO standards
is less than 5 pages long, and, as I recall, each ISO standard costs
~$100...what a rip-off!)
I'm willing to buy them. I've already gotten the ISO 15765-1 doc which
just refers to the other relevant docs. The ISO 15765-4 seems the most
interesting, but I can't find that for sale anywere. Do you have any
references or information availabe. Or know where I can pick up that
(or ay related) documents.
Those damn ISO committees! It looks like that spec has been in
"committee" for at least 5 years, and since it is not "approved", it still
is not for sale. Somehow Ford, GM, Mercedes and others have managed to
make it work for OBD-II without a standard! Welcome to the generic "scan
tool" business! :-)
I'm looking at going with the MCP2515 controllre IC, though I'm not sure
how fast of an oscillator it needs.
For 1 MHz OBD-II CAN, you will need 16 MHz clock with that chip.
Will a ceramic resonator work? I find them easier to deal with than
crystals. And they're cheaper :)
CAN-bus at 1 Mbps has pretty tight timing. You need to look at the spec
for the chip and the specs for your resonator. Me? I've been using
"cheap" 16 MHz crystals.
p.s. I've posted a simple schematic of how I think the AVR should hook
up to the CAN controler and transiever. If you wouldn't mind looking at
it -- am I missing anyhthing? I'm not sure what resitor values I should
use for the CAN termination and the slew rate control... I'm picking 120
and 10, respetctivly, as that's what I've seen used elsewhere...
Posted where? A 120 ohm termination resistor is correct, but normally the
vehicle itself supplies this.
Best regards,
Bruce
--
Bruce D. Lightner
Lightner Engineering
La Jolla, California
Voice: +1-858-551-4011
FAX: +1-858-551-0777
Email: address@hidden
URL: http://www.lightner.net/lightner/bruce/
- [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Reza Naima, 2004/07/23
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Alan Kilian, 2004/07/25
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Reza Naima, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Bruce D. Lightner, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Reza Naima, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?,
Bruce D. Lightner <=
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Richard Urwin, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Bruce D. Lightner, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Alan Kilian, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Brandon Matthews, 2004/07/26
- Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Reza Naima, 2004/07/26
Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?, Graham Davies, 2004/07/26