[Fwd: Re: [avr-chat] AVR and Hardware For Reading Automotive On-Board Diagnostics Connector?]

[Robert L Cochran]

Vincent Trouilliez wrote:
> On Wed, 04 Mar 2009 20:26:39 -0500
> Robert L Cochran <address@hidden> wrote:
>
>   
>> Is there an AVR that is especially good for reading data from an
>> automobile's on-board diagnostic (OBD) connector? Is there already
>> hardware that can do this: a cable for plugging into the OBD port, and a
>> board which can read the codes coming from the port? By automobile, I
>> mean an automobile built for the North American market. I assume that
>> the OBD connector varies in style and pinout from country to country?
>>
>> I know my auto mechanic has a device weighing 25 kilograms with a long
>> heavy cable terminated by a fat connector that plugs into my OBD port,
>> reads the trouble codes, and displays them on a screen. That is pretty
>> much what I want to do, along with intelligent matching of what the
>> codes probably mean, but I want the smallest possible form factor.
>>     
>
> What a coincidence ! I am precisely developping an OBD handheld device
> using an AVR. Most of the hard work has been done and it's nearing
> completion, so maybe I can share my experience.
>
> - Choice of AVR chip: I am using an ATmega32 at 16MHz. It's plenty
> enough : my reader (also datalogger) is featureful with a user friendly
> interface, yet the code is only about 10KB. All you need is an UART to
> connect to the care's ECU, so just about any small AVR will do it,
> nothing special. For a basic code reader, a mega32 would be way
> overkill ! There is no need for any extra hardware/boards/module...
>
> As for the OBD plugs/connectors themsleves, IIRC they are not available
> anymore, or at least you would have to be very lucky or motivated to
> find some. I sure would love one, would be much more practical and
> elegant than stuffing leads by hand into the car's socket !
>
> Also, I am using the UART because my reader is dedicated to a
> particular car (4 pot Lotus Esprit, 1989-1996 MY), and it happens to
> use a half-duplex serial port. However IIRC, the OBD also used a PWM
> interface so it would be different.
>
> You will have to do your own research to gather information about the
> particularities of each and every car you want to interface to, since
> they all have their particularities in how they implement trouble
> codes. Google will find you lots of people in the US who like to fiddle
> with their old car's ECU...
>
> As a starting point here is the website of the chap who made it all
> possible for Lotus Esprit fans to make their custom ECU reader, he did
> all the hard work of figuring out the Lotus protocol. It has also links
> to general purpose resoources on OBD and OBD II, to get you started.
>
> http://www.andywhittaker.com
>
> Doing a universal tool would be a huge PITA I hardly Fancy. My luck was
> that I wanted to design an OBD device targeted specifically at a single
> car model, so as a result my program is much more simple and small I
> guess, than what it would be if I had to make it work with any and all
> OBD compliant car on the planet !
>
> But if you just want a simple/basic code reader and nothing else, then
> there are plenty of tiny handhled devices that do just that and cost as
> low as 30 Euros IIRC ! Again, just search the net, shouldn't take more
> than a few seconds to find one.
>
> Ah, in case you didn't mean OBD, but OBD-II, then that's another story
> altogether, I have no idea how complicated the OBD-II protocol is
> compared to OBD. Maybe one day if I win the lottery, I will get a Lotus
> Esprit V8, these are more modern than the 4 pot, they feature OBD-II
> not OBD. So I am sure I would want to redesign my ECU device to talk
> OBD-II ! ;-)
>
>
> Good luck anyway. I have had a lots of fun designing my custom ECU
> device ! :-) So much fun that I am asking for more, and have already
> plans to make a second version of it, with more features and a more
> elaborated user interface.
>
>
> Hope that helps !
>
>
> --
> Vince
>
>   
Thank you Vince! And Peter, and Dan. Vince, do you have a picture of
your circuit?

I do mean OBD-II, for North American-market cars built 1996 and later.

What I'm interested in doing is buying some device like the Auto XRay
Code Scout 1500, which looks like it is pretty cheap on Ebay, and
connecting it somehow to a wifi (802.11a/b/g/n) transciever like the
Rabbit RCM5600W

http://www.rabbit.com/products/rcm5600W/index.shtml

and sending that information to a computer on my network for logging and 
analysis.

Do you think there are gadgets out there that already do this for me?

Basically I want to get the codes from the car to my computer wirelessly, with 
a quick plug-in, wait for green light, unplug action that takes only a few 
seconds.

I don't know if there are wireless AVR chips that can do the same thing as the 
Rabbit module mentioned above. 

And Vince -- perhaps you can go to a mechanic you are friendly with and see if 
there is an old OBD cable that you can buy, then cut the cable to the right 
length for your project, and plug it into the car's OBD port with the 
connector. Then connect the loose wires at the other end to your circuit board 
or perhaps build a custom Molex connector of some sort.

Thanks

Bob