Re: [avr-gcc-list] Anyone interface an AVR with a CAN bus?

[Bruce D. Lightner]

Richard Urwin wrote:

> On Monday 26 Jul 2004 7:18 am, Bruce D. Lightner wrote:
>
> > 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! :-)
>
> You may know this, but the base CAN protocol is available on the net. 
> Google for "CANbus".

True.  What Reza was talking about is the higher-level OBD-II protocols 
that (per US Federal regulation) every vehicle using the CAN-bus to 
deliver OBD-II emissions data must follow.  (Any vehicle sold after 1995 
in the US must have an OBD-II connector supplying "standardized" emissions 
data.  Starting with model year 2003, CAN-bus became a new option for 
providing this data.)

Among other things, the OBD-II allows anyone to monitor their vehicle's 
performance in real-time.  Besides things like pending and active 
diagnostic trouble codes (DTCs), the OBD-II bus will also supply all kinds 
of other interesting data, such as vehicle speed, engine RPM, intake air 
temperature, ignition timing, engine load, etc.  If you know the 
"manufacturer-specific" (i.e., "secret") codes, you can also learn (and 
sometimes change) things like the road speed at which your engine computer 
shuts off power to the fuel pump!

Atmel's AVR chips (and "avr-gcc") offer an inexpensive way to access this 
OBD-II data.

Best regards,

Bruce

--
 Bruce D. Lightner
 Lightner Engineering
 La Jolla, California
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