OBDII Protocol for vehicle

alcomen · Joined: 13 Dec 2006 Posts: 10

someone already sae a project of communication between the microcontroller and electronic fuel injector using OBDII protocol?

this project is used for read parameters of the engine cars (General Motors).

Alessandro

filipe.oliveira · Joined: 17 Apr 2008 Posts: 12 Location: Portugal

it's a good idea..
last year, I searched something but i didn't had much time, so i had to leave this subject, but if anyone know something,... tell Laughing

alcomen · Joined: 13 Dec 2006 Posts: 10

One of the ways is the CI ELM323, this component is a converter OBDII to RS232, but I don´t find this component in Brazil.

See http://www.elmelectronics.com/

Any additional information help much.

Alessandro

crystal_lattice · Joined: 13 Jun 2006 Posts: 164

Search the forum for OBD2 or the like, there was an individual whom was making a open source "copy" of the ELM323 chip, can't remember the exact details but think its basically a PIC with the low end comms stuff handled on it and enables it to connect to a PC serial port. If not mistaken the ELM323 hex is available but no source code. Sorry can't help any more, will try and find the thread when i have time...

Edit: http://www.obdchip.com/

Keep us posted of your developments, as i'm sure many will appreciate!

alcomen · Joined: 13 Dec 2006 Posts: 10

I am taking a electronic fuel injector for protocol test, but I willl need this component (ELM323).

I have dome some projects with a graphic LCD as a Digital Scope (find in youtube for "alcomen"), so I would like use this LCD type for an on-board computer for vehicles.

This a difficult job because this protocol is not reviewed by anyone who understand this area.

Alessandro

dyeatman · Joined: 06 Sep 2003 Posts: 1935 Location: Norman, OK

You need to do some searching with Google (use the keyword OBDII).
There is a LOT of stuff out there.

Basically there are four protocols for the various types of
vehicles (Ford, GM, Chysler and foreign) J1850 PWM, J1850 VPW,
ISO9141-2, ISO14230-4. These were used from 1995 to 2003 and then
there is the CAN interface that appeared in the 2003-2005 model years.

I learned by spending more than two months researching before I
wrote my first OBDII code based on the 16F series chips.

There are two ISO Standards documents (J1850 and ISO9141 that cost
serious $$) I had to buy that that detail virtually everything there is to
know about the protocols. Then you have to research the individual
manufacturers for their specific adaptations.

Both of my interfaces are based on the PIC series of chips and most of
the ones I know about (ELM, BR3 etc.) are as well.

I will get you started by pointing you here for the protocol "basics":
http://obddiagnostics.com/obdinfo/info.html

Just to warn you it likely won't be quick, easy or cheap to get all the info
and get your first one built from scratch unless someone hands it to you.
Your best bet is the ELM chip if you want to get something going quickly.

Good Luck!

alcomen · Joined: 13 Dec 2006 Posts: 10

although such a protocol has to be on the market years, remains very limited any information.

I read much and be patient.

I need import this component (ELM).

Thanks for your information, any new information is always welcome!

dyeatman · Joined: 06 Sep 2003 Posts: 1935 Location: Norman, OK

Yep, the info is limited because (in my opinion) the Manufacturers want to
sell their high priced scan tools to the dealerships and limit the alternatives
on the market. I am sure they have their own explanations...

Between the VPW used by GM, the PWM used by Ford and the ISO9141
used by Chrysler the software has be pretty flexible.

In reality, once you understand the requirements of the various modulation
types the basic I/O driver coding is pretty straight forward. A good o'scope
for waveform analysis and monitoring is an absolute requirement!

Some recommendations:
1. My cars stay outdoors since my garage is full of tools and workbenches
so I made a 50' interface cable to run from the car to my workbench
during the debugging phase which made it possible to work inside
regardless of the weather.

2. There are several hardware interface designs for level translation. Here
is one good article:

http://www.planetfall.com/~jeff/obdii/

3. Here is another good source for info:
http://www.opendiag.org/

Dave

alcomen · Joined: 13 Dec 2006 Posts: 10

this informations is very good,

The VPW that I will used is the ISO14230 by GM. I think that if I not have the ELM Chip, don´t start the tests.

while this is only theoretical studies. I save all documents sending by topic.