Comments on: J1850 VPW Interface

By: Humberto

Humberto — Mon, 25 Jul 2011 20:28:38 +0000

Hello Michael,

I finally have my interface working. I used Do..Loop cicles for timing decode.

I tested it with a Stand-Alone workbench PCM. No other modules are on bus. So I guess PCM is interrogating othe rmodules.

this is the output:

J1850VPW 1.34

48 EA 10 0A 00 72
E8 FF 10 03 B3
48 EA 10 0A 00 72
49 92 10 01 BE
49 92 10 01 BE
48 EA 10 0A 00 72
49 92 10 01 BE
48 EA 10 0A 00 72
E8 FF 10 03 B3
49 92 10 01 BE
48 EA 10 0A 00 72
49 92 10 01 BE
48 EA 10 0A 00 72
49 92 10 01 BE
E8 FF 10 03 B3
48 EA 10 0A 00 72
49 92 10 01 BE
48 EA 10 0A 00 72
49 92 10 01 BE
48 EA 10 0A 00 72
E8 FF 10 03 B3
48 EA 10 0A 00 72
E8 FF 10 03 B3
here it keeps repeating this message every second…
E8 FF 10 03 B3
E8 FF 10 03 B3
E8 FF 10 03 B3

By: Michael

Michael — Fri, 22 Jul 2011 10:51:05 +0000

You will hardly find documentation of car specific bus data.
It’s all proprietary information kept secret by the manufactures.

There are only a few SAE specification describing some basic data frames.
VPW frame structure is described in SAE J1850.

By: Humberto

Humberto — Fri, 22 Jul 2011 06:14:23 +0000

Hello Michael, Is I promised some months ago I started to learn better the VPW protocol. instead of try to translate your C code, I finally understanded nicely the VPW trnsitions pattern. I got an Digital Storage Oscilloscope and with just the Key on “ACC” position, get lot of bit patterns from my OBDII connector. As you indicated, there is a lot of data!

I captured a complete packet with SOF. After printing the pattern I was able to decode by hand the bytes:

$E8 $FF $40 $03 $ED

Now I’m in the way to start likely from scratch using Bascom Avr, and using your code as guide, but will try to implement my own timing decode routines, based on Bascom language and M2560 chip.

Do you know where could I get reference for the above packet ? I think this is data exchanged between the modules of my car.

By: Humberto

Humberto — Fri, 24 Jun 2011 05:09:02 +0000

Thanks Michael,

I will start to translate to Bascom.

I will keep inform about progress : )

By: Michael

Michael — Thu, 09 Jun 2011 09:56:21 +0000

Nope, I do not sell my projects stuff.

By: J.N.

J.N. — Mon, 06 Jun 2011 17:44:16 +0000

Possible to buy from you an already build PCB board ?
I am so board with soldering irons

By: astaza

astaza — Sat, 09 Apr 2011 02:16:55 +0000

hello is this will work with honda cars?
thank you so much

By: Michael

Michael — Tue, 22 Mar 2011 17:17:40 +0000

There was a general problem with downloads since last update. Has been fixed.

By: y2kevin

y2kevin — Tue, 22 Mar 2011 13:56:27 +0000

pardon me for being ignorant but where do I download source code 1.06 to flash the project with?

By: Michael

Michael — Thu, 17 Feb 2011 06:58:36 +0000

As far as I know For uses J1850 PWM not VPW. You can use any USB-RS232 Adapter with the interface.