Hey-

I put a scope on these two pins (1 & 13) and found that pin 1 seems
to
float up around battery voltage while pins 13 has a PWM signal with a
frequency of about 100 Hz.  The pulse width is somewhere around a
couple of hundred microseconds at idle, and widens when I press the
throttle.  I don't know if it is throttle position (this car is drive
by wire) or engine speed, or boost, or what.

Ring any bells?

Brian

Jeff & Dale-

Thanks for all your feedback.  Let me try to answer some of your
counter-questions:

> My memory is fuzzy. Are you sure that 1 and 13 aren't power or
ground?
> My 98 Passat's connector has two grounds and one power, and a K
line.
> My GTI also has an L line. I can look it up later if you like.

I'm certain that I've got the pins correct.  If I had them backwards,
then pins 4 and 5 (the grounds) wouldn't match up to holes with pins.
I have tried to include a picture of my S4's port to show you what I
see.  If it doesn't show up below, then use this link:

<IMG SRC="http://www.guisoft.com/pics/s4-obdii.jpeg">


> I don't claim to be an expert, but the schematic on my web page
works
> and is probably a good starting point for you. It's mostly a clone
of
> the VWtool interface. In your case, you can use a simpler interface:
> since your car doesn't connect the L line to anything, you can
leave off
> an optoisolator and a few other parts.

I will either use a circuit like that, or the L9637 part.  They
basically do the same thing.  The optoisolation might be unnecessary
in
my application because I'm looking into powering my hardware from the
battery power on the OBDII connector.

> I'm unclear on what your long-term goal is. Did you want something
you
> would leave running in your car for data logging?

Basically, yes.  I want something that on powerup will configure the
port to continuously output one or more variables defined during
initialization.  Then, another command from the external hardware
will
cause it to either output other data, or cease.

>I don't know if your S4 is different, but on my car pins 1 and 13
> aren't used.  Are you sure you aren't looking at the plug upside
> down?

I don't think so.  The pic above should clarify this.

I'm going to keep looking around my S4 resources to see if I can find
out what the pin 1 and 13 are for.  In the meantime, I think I will
begin playing with the K line.

Thanks for your suggestions, and I'll keep you posted.

Brian

Perhaps I can help. On my 1996 A4, it uses pin 7 as the K line, pin 5 as ground,
and pin 16 as V+. The L line isn't used. I don't know if your S4 is different,
but on my car pins 1 and 13 aren't used.  Are you sure you aren't looking at the
plug upside down? Looking down at the plug in my car: (excuse the ascii drawing)

            V+
            16 15 14 13 12 11 10 9
            _______________________
           /O  O  O  O  O  O  O  O \
          /                         \
         /  O  O  O  O  O  O  O  O   \
        /____________________________ \
            8  7  6  5  4  3  2  1
               K    Gnd

The adapter in the opendiag web site does work very well on my car. I have used
it with both the VAG-Com beta software currently available for download at

http://www.ross-tech.com/vag-com/index.html

and the Baum tools OBD2SCAN v1.2.60 software, which for some reason is available
for download on their website at:

http://www.baumtools.com/softupdt.htm

The VAG-COM software is VW/Audi specific, and can talk to the airbag, ABS, AC,
and other systems. The Baum software is true OBDII scan software that can show
graphs and other real-time data. I think that when the VAG-COM is done, it will
also be able to show real-time data.

Hope this helps.

Dale Kirstein


>>> -----Original Message-----
>>> From: blg@... [mailto:blg@...]
>>> Sent: Wednesday, July 26, 2000 12:15 AM
>>> To: opendiag@egroups.com
>>> Subject: [opendiag] Re: Anyone use the L9637 ISO 9141 Interface chip
>>> from ST?
>>>
>>>
>>> Jeff-
>>>
>>> I guess I'm a little confused on this... The car i'm working on is a
>>> 2000 Audi S4.  The ODBII connector only has a single ISO 9141 K line
>>> for communication, so I assumed I need to use that line to talk VAG
>>> protocol.  I'm I confusing terms here?
>>>
>>> There is an additional set of pins on the OBD connector that may be
>>> what you are talking about.  Pins 1 and 13 have pins in them, but I
>>> could never find a pinout on the web that shows these as other than
>>> "discretionary".  Are these pins for the VAG interface to which you
>>> are referring?
>>>
>>> This stuff is new to me, so I appreciate your comments.
>>>
>>> Brian
>>>
>>>
>>>
>>>
>>> --------------------------------------------------------------------<e|-
>>> Still looking for the complete Application Server solution?
>>> Find answers and a $75 gift certificate at the Intraware App Server
>>> Webinar. Sign up at:
>>> http://click.egroups.com/1/6756/13/_/834286/_/964592114/
>>> --------------------------------------------------------------------|e>-
>>>
>>> To unsubscribe from this group, send an email to:
>>> opendiag-unsubscribe@onelist.com
>>>
>>>
>>>
>>>

On Wed, Jul 26, 2000 at 06:15:04AM -0000, blg@... wrote:
> I guess I'm a little confused on this... The car i'm working on is a
> 2000 Audi S4.  The ODBII connector only has a single ISO 9141 K line
> for communication, so I assumed I need to use that line to talk VAG
> protocol.  I'm I confusing terms here?

ISO9141-2 specifies that the K line communicate with the tester at
10.4kbps.  You can't obtain 10.4kbps on a normal RS-232 port, so it is
necessary to have an interface chip that can do some buffering for you.

In the proprietary VAG mode, you can communicate at 9600bps on the
K line.  In this mode, your hardware only needs to be concerned with
level shifting between RS-232 (-3V and +3V thresholds) and automotive
voltages (somewhere around 1V and 8V thresholds.)  Everything else can
be done in software.

The VAG mode is not strictly OBDII, but as far as I know, it's the
only mode in which you can access proprietary data blocks. (I could
be wrong.)

> There is an additional set of pins on the OBD connector that may be
> what you are talking about.  Pins 1 and 13 have pins in them, but I
> could never find a pinout on the web that shows these as other than
> "discretionary".  Are these pins for the VAG interface to which you
> are referring?

My memory is fuzzy.  Are you sure that 1 and 13 aren't power or ground?
My 98 Passat's connector has two grounds and one power, and a K line.
My GTI also has an L line.  I can look it up later if you like.

The same K wire is used for either protocol.  My guess is that only the
5bps initalization sequence differs.  I have not analyzed the VAG protocol
yet, I'm just using VWtool.  Someone else has reported that Ross-Tech's
VAG-COM software also works (which for the time being, is free.)

> This stuff is new to me, so I appreciate your comments.

I don't claim to be an expert, but the schematic on my web page works
and is probably a good starting point for you.  It's mostly a clone of
the VWtool interface.  In your case, you can use a simpler interface:
since your car doesn't connect the L line to anything, you can leave off
an optoisolator and a few other parts.  I'd guess that you could build
the thing for a minimum of $5-$10.

I'm unclear on what your long-term goal is.  Did you want something you
would leave running in your car for data logging?

I hope I've been helpful.

Regards,

Jeff

Jeff-

I guess I'm a little confused on this... The car i'm working on is a
2000 Audi S4.  The ODBII connector only has a single ISO 9141 K line
for communication, so I assumed I need to use that line to talk VAG
protocol.  I'm I confusing terms here?

There is an additional set of pins on the OBD connector that may be
what you are talking about.  Pins 1 and 13 have pins in them, but I
could never find a pinout on the web that shows these as other than
"discretionary".  Are these pins for the VAG interface to which you
are referring?

This stuff is new to me, so I appreciate your comments.

Brian

Interesting.

If you have a VW or Audi (or Seat or Skoda) you'd probably be better
off using the VAG protocol.  No interface chip is required -- just a
few transistors.  And you get access to more information than you could
using ISO9141.  The VAG protocol is 9600 bps async (half duplex), with
the exception of the handshake.

Regards

Jeff

This part seems to handle the interface from ISO 9141 to RS-232.  It
doesn't provide optical isolation, but depending upon what you're
interfacing to, it may not be necessary.  I'd like to put togther
something that will allow me to select an engine parameter, like say
engine speed, and have the car continually spit that variable out on
the port until I tell it to stop.  I'd rather not buy an interface
cable since I want to incorporate the electronics into an external
module that will be processing the data.

The datasheet for the L9637 can be found at:

http://eu.st.com/stonline/books/pdf/docs/1765.pdf

Any ideas?

Brian Gery

Today I made some minor updates to my diagnostic interface page:

* Added Digi-Key part number for 2501 Optoisolator
* Added information on Multiplex Engineering's OBDII cable
* Added link to Ross-Tech's VAG-COM software
* Added section on part substitutions

More suggestions are welcome.

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

Regards,

Jeff

On Fri, Jul 21, 2000 at 08:20:10PM -0500, Jeffrey Nabozny wrote:
> Is there anyone here with the capabilities to make the PCB? Assembling
> and soldering are my limits and I'd really like to make one of these cables.
> I'd appreciate any help someone could give me.

Making the PCB is actually not that difficult.  If you would like, I
will post instructions.  You will need a drill press and some really
small bits.  I used a dremel tool with the drill press attachment.
You also need access to a laser printer.  (A photocopier might work okay.)
Everything else you can purchase cheaply at Radio Shack.  I'd estimate
that it cost me about $20 to make my first PCB.  The time involved is
an hour or two at the most.

Also, I now have a source for the OBDII connector itself for about
$15+s/h.  That's a lot cheaper than the $49 price B&B has it for...
I need to update the web page!

Regards,

Jeff

Is there anyone here with the capabilities to make the PCB? Assembling
and soldering are my limits and I'd really like to make one of these cables.
I'd appreciate any help someone could give me.

at  http://www.powertv.com/morgan/photos/opendiag.html

This'll come in handy 'cause VWTool's list is encrypted.

-Morgan

On Wed, Jul 05, 2000 at 12:58:13PM -0500, Jeff Noxon wrote:
> The VAG protocol runs at 9600bps, which greatly simplifies the hardware
> required to connect the vehicle to a PC.  The OBD-II standard specifies
> 10.4kbps.

Allow me to correct my own misinformation.  OBD-II does not specify
10.4kbps.  It is part of the ISO9141-2 interface specification...

Regards,

Jeff

--
"For a list of ways technology has failed to improve your quality of life,
press seven."

Barry,

So far most of us have been playing with the VAG proprietary protocol.
I have a copy of VWtool, which works with the schematic on my website.
I have not made any attempt to reverse engineer this protocol, although
at least one other person has spent some time with it.

The VAG protocol runs at 9600bps, which greatly simplifies the hardware
required to connect the vehicle to a PC.  The OBD-II standard specifies
10.4kbps.

Check out this web site:

http://www.ross-tech.com/vag-com/index.html

This guy has some beta software you can download for free.  It is supposed
to work with the VAG protocol, and should be compatible with the schematic
on my website.  You may be able to reverse engineer what you want out of it.

Also, the Society of Automotive Engineers (SAE) sells a book that contains
most of the parts of the OBD-II spec.  I think it sells for about $95,
and a new version comes out annually.  I don't remember the name of it,
but you can probably find it on the SAE website.  I haven't bought a copy
(yet), but I do have copies of the ISO 9141-2 spec which came in handy
while working on the hardware interface.  SAE sells ISO9141-2 as well...

If you want to do any programming, I think you'll find the SAE book very
useful.

If you write any software, I encourage you to release it under the GPL so
that others can contribute.  VW/Audi users everywhere could really use a
good, free tool that can be modified easily...

Good luck,

Jeff

On Wed, Jul 05, 2000 at 08:15:55AM -0000, barry@... wrote:
>   There is a lot of talk about the hardware here, but does anyone
> have any tips on programming for this interface? I am trying to find
> out Engine Speed, Load, and vehicle speed while the car is running.
> using VB or C++.
>
>   If anyone could point me in the right direction i would be very
> grateful.

Hello,
   There is a lot of talk about the hardware here, but does anyone
have any tips on programming for this interface? I am trying to find
out Engine Speed, Load, and vehicle speed while the car is running.
using VB or C++.

   If anyone could point me in the right direction i would be very
grateful.

Barry Webb

On Mon, May 08, 2000 at 04:20:09PM -0300, Bruce Miller wrote:
> Hi Jeff, just tried to download the new files - inconsistent data was the
> error message.

I can't reproduce that problem.  Did you rename the files?  Copy the
two files (iso_b1.sch, iso_b1.brd) into an otherwise empty directory.
Then run Eagle and try to open one of them.  The forward/back annotation
is working for me, and the board passes the design/electrical rule checks.

This may be a problem with the Windows version of Eagle.  I'll download
it and try it out if this does not fix things for you.

Please let me know how it goes.

Thanks

Jeff

Jeff Noxon wrote:

> Here's my first contribution:
>
> http://www.planetfall.com/~jeff/obdii/
>
> The site contains photos, a computer-generated schematics, a board layout,
> and so on.  Everything is distributed under the GPL.
>
> Please feel free to link to this page from the OpenDiag web page.
> I hope this effort makes it easier for other folks to get a device up
> and running.  If you have any suggestions or questions, let me know.
>
> Enjoy,
>
> Jeff
>
> --
> Linux: The Ultimate Windows Service Pack

Hi Jeff, just tried to download the new files - inconsistent data was the
error message.
-Bruce
--
Bruce Miller       EMAIL:bmiller@...
Chief Technician     PH:(506) 453-5070
University of New Brunswick, ECE Dept.  FAX:(506) 453-3589
1992 VW PASSAT G60 SYNCRO WAGON 197,000km   AT Stage II

Here's my first contribution:

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

The site contains photos, a computer-generated schematics, a board layout,
and so on.  Everything is distributed under the GPL.

Please feel free to link to this page from the OpenDiag web page.
I hope this effort makes it easier for other folks to get a device up
and running.  If you have any suggestions or questions, let me know.

Enjoy,

Jeff

--
Linux: The Ultimate Windows Service Pack

Jeff Noxon wrote:

> All,
>
> I have a functional circuit on a breadboard, based mostly on the design
> posted to the Opendiag web site.  It has been tested on a 98 Passat and
> a 98 GTI.  The GTI uses two-wire communications (K & L), while the Passat
> uses only the K-wire.
>
> I have also drawn a schematic and board layout in Eagle (www.cadsoft.de).
> I plan to make these files available under GPL very soon.  I want to
> make a prototype board first, to make sure it works correctly.
>
> The single-layer board measures 1.25" x 3.5".  No surface-mount
> components are used.  On one end is a female DB-9 for connection to
> a laptop computer.  On the other end is a male DB-9 for connection to
> the automobile.  The pinout of the male DB-9 is the same as that used
> by the J1962 cable sold by B&B Electronics.  B&B sells the cable for
> $45 shipped.  Although it's expensive, it's a very nice moulded cable
> and it was worth the convenience to me.
>
> I have been thinking about having several boards made professionally.
> If anyone would be interested in a kit including all the parts and a
> circuit board, please contact me.  I would probably need 10 people, and
> the price will probably be around $35-40.  This is for an unbuilt kit
> with no software!  If you have used a soldering iron before, it should
> take less than an hour to build.  This is not a profit thing for me!
> I am just doing this to gain experience.
>
> Thanks!
>
> Jeff

Hi Jeff, I have a BoardMaker 912 that can mill out PC boards
for small quantities, and prototypes. If I had the schematic and/or
a gerber file, I can make boards (double sided slightly more difficult).
-Bruce




--
Bruce Miller       EMAIL:bmiller@...
Chief Technician     PH:(506) 453-5070
University of New Brunswick, ECE Dept.  FAX:(506) 453-3589
1992 VW PASSAT G60 SYNCRO WAGON 186,000km   AT Stage II

I'm definitely interested, Jeff.

-----Original Message-----
From: Jeff Noxon <jeff-opendiag@...>
To: opendiag@egroups.com <opendiag@egroups.com>
Date: Wednesday, May 03, 2000 12:40 PM
Subject: [opendiag] Circuit board


>All,
>
>I have a functional circuit on a breadboard, based mostly on the design
>posted to the Opendiag web site.  It has been tested on a 98 Passat and
>a 98 GTI.  The GTI uses two-wire communications (K & L), while the Passat
>uses only the K-wire.
>
>I have also drawn a schematic and board layout in Eagle (www.cadsoft.de).
>I plan to make these files available under GPL very soon.  I want to
>make a prototype board first, to make sure it works correctly.
>
>The single-layer board measures 1.25" x 3.5".  No surface-mount
>components are used.  On one end is a female DB-9 for connection to
>a laptop computer.  On the other end is a male DB-9 for connection to
>the automobile.  The pinout of the male DB-9 is the same as that used
>by the J1962 cable sold by B&B Electronics.  B&B sells the cable for
>$45 shipped.  Although it's expensive, it's a very nice moulded cable
>and it was worth the convenience to me.
>
>I have been thinking about having several boards made professionally.
>If anyone would be interested in a kit including all the parts and a
>circuit board, please contact me.  I would probably need 10 people, and
>the price will probably be around $35-40.  This is for an unbuilt kit
>with no software!  If you have used a soldering iron before, it should
>take less than an hour to build.  This is not a profit thing for me!
>I am just doing this to gain experience.
>
>Thanks!
>
>Jeff
>
>------------------------------------------------------------------------
>SHOPPING for DEALS? The merchants at BuyItOnline.com are offering up
>to 30% OFF great gear, wear, gadgets and more, now through April 15,
>2000. Real stores. Real Deals. Real Easy. Go get something great!
>http://click.egroups.com/1/3025/6/_/834286/_/957375634/
>------------------------------------------------------------------------
>
>To unsubscribe from this group, send an email to:
>opendiag-unsubscribe@onelist.com
>
>
>
>

All,

I have a functional circuit on a breadboard, based mostly on the design
posted to the Opendiag web site.  It has been tested on a 98 Passat and
a 98 GTI.  The GTI uses two-wire communications (K & L), while the Passat
uses only the K-wire.

I have also drawn a schematic and board layout in Eagle (www.cadsoft.de).
I plan to make these files available under GPL very soon.  I want to
make a prototype board first, to make sure it works correctly.

The single-layer board measures 1.25" x 3.5".  No surface-mount
components are used.  On one end is a female DB-9 for connection to
a laptop computer.  On the other end is a male DB-9 for connection to
the automobile.  The pinout of the male DB-9 is the same as that used
by the J1962 cable sold by B&B Electronics.  B&B sells the cable for
$45 shipped.  Although it's expensive, it's a very nice moulded cable
and it was worth the convenience to me.

I have been thinking about having several boards made professionally.
If anyone would be interested in a kit including all the parts and a
circuit board, please contact me.  I would probably need 10 people, and
the price will probably be around $35-40.  This is for an unbuilt kit
with no software!  If you have used a soldering iron before, it should
take less than an hour to build.  This is not a profit thing for me!
I am just doing this to gain experience.

Thanks!

Jeff

On Wed, Apr 19, 2000 at 04:42:00PM +0100, ZJ Laczik wrote:
> What is the 5 Baud startup sequence to get the interface into
> the standard 9600 Baud serial mode?

If/when I get mine working I'll post it.  I have access to several HP
serial analyzers/data loggers.

Later

Jeff

I am not an electronics guru, but know enough that I can build
one if I had schematics and a parts list. Hopefully you can get
yours built. I'm also confident that in the not too distance future,
this stuff will be inexpensive to get a hold of.
-----Original Message-----
From: Jeff Noxon <jeff-opendiag@...>
To: opendiag@egroups.com <opendiag@egroups.com>
Date: Thursday, April 20, 2000 1:06 PM
Subject: Re: [opendiag] Schematic


>On Thu, Apr 20, 2000 at 12:25:30PM -0500, Jeff Noxon wrote:
>> Does anyone have a cleaner schematic of the RS-232 to L/K diagnostic
>> interface?
>>
>> I follow the one on the web site for the most part, but a few things
>> confuse me.
>
>In particular, what is the value of the Zener?
>
>Also, why no current limiting resistors on the input to the optoisolators?
>Is it limited already?
>
>I guess the rest makes sense.  I'd like to breadboard this over the weekend
>if I get a chance.
>
>Thanks in advance for any help
>
>Jeff
>
>------------------------------------------------------------------------
>INSTANT RESEARCH. Check out Hoover's Online: Info on 50,000+
>companies, 300 industries, IPO coverage, stock information &
>more. Click here!
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>
>To unsubscribe from this group, send an email to:
>opendiag-unsubscribe@onelist.com
>
>
>

On Thu, Apr 20, 2000 at 12:25:30PM -0500, Jeff Noxon wrote:
> Does anyone have a cleaner schematic of the RS-232 to L/K diagnostic
> interface?
>
> I follow the one on the web site for the most part, but a few things
> confuse me.

In particular, what is the value of the Zener?

Also, why no current limiting resistors on the input to the optoisolators?
Is it limited already?

I guess the rest makes sense.  I'd like to breadboard this over the weekend
if I get a chance.

Thanks in advance for any help

Jeff

Does anyone have a cleaner schematic of the RS-232 to L/K diagnostic
interface?

I follow the one on the web site for the most part, but a few things
confuse me.

Thanks

Jeff

Hi,

I would like to make some progress over Easter, but would
need some more info on
> At start of communications, RTS has a 2nd duty:
> it does the 5 baud startup sequence.

What is the 5 Baud startup sequence to get the interface into
the standard 9600 Baud serial mode?

Thanks

John

I just signed up for this list. I am very interested in building
my own RS-232 to ODB-II cable for future use on my VW. I
am not an electrical expert but can solder well enough that
I have built my own Amiga computer cables in the past. From
what I see so far, I'll need more guidance to build my own cable.
Has anyone picked this project up to try to give more
explicit building instructions? Is there strong interest yet? I'm
sure in a few years, demand for this stuff will be high enough
that companies will fill this void for us backyard mechanics but
I don't want to wait. lol

I somehow overlooked adding these part numbers:
NEC "High Isolation Voltage SOP Multi Optocoupler"
parts PS2701-1 and PS2701-2. Spec sheets available
at

All optocouplers:
http://www.cel.com/prod/prod_optdevs.asp

2701 specifically:
http://www.cel.com/pdf/datasheets/ps2701.pdf

We don't have to use these (DIP instead of
SOP packages would be more convenient),
but if we're going to slavishly copy the design,
we should check the specs of the optos used.

J. Grable was conservative: he used separate
optos for each direction.  You could use a
single quad (and waste one).

His design uses RTS as a constant voltage
source for transistor side of the receiver.
If you are doing RS-232 and don't have access
to power on the computer side, that's a reasonable
design, but if you *do* have power, there are
other options.  Doing it this way puts another
burden on the software- it has to keep RTS
on all the time & some drivers don't allow
software control of those lines unless you go
around the driver completely (I think PalmOS is
like that).

At start of communications, RTS has a 2nd duty:
it does the 5 baud startup sequence.

DTR is used as a pulldown for the RXD input to the
computer.  I think my note says -12V nominal.

Incidentally, I have a spec sheet for a Sipex +3 to +5V
RS-232 line driver/receiver in my notes.  I believe
that's because it's the part used in the Palm and
I was concerned about current draw on DTR and
RTS from this part.  The resistors used are pretty
small ('cause a laptop has no trouble supplying
that much current) & could be a lot bigger as long as the
input impedance of RXD, etc. are high.

Hope this helps.  I've asked the student to contribute
his schematic & parts list.  Let's hope he helps us
out.

-M

=========================================
The weekend: brought to you by organized labor.

Hi Gang,

I've been tooling with the idea of building an interface for my
B5 Passat.  I purchased the SAE specs on the electrical interface
and planned on building an RS232 converter around an Atmel AVR chip,
a few optoisolators, and a MAX232 or similar.  I never got very far,
because I am a software person and my hardware skills are minimal.
(I have a rough schematic but I have not tried it.)

I purchased a laptop computer for the specific purpose of buying the
Carcomp VWtool to run on it.  This was just days after the unfortunate
passing of the gentleman behind Carcomp.  :(

I am also building a computer which will live in my car.  It is based
on a TMC single board computer, with an AMD K6-2 @ 120 MHz (no cooling
needed, low power).  I built my own switching power supply to run
the computer, +5 @ 5A & +12 @ 30ma.  The system runs Linux, and also
has a 12 GB Travelstar drive, a PCMCIA WaveLAN card (for data transfer
between my home computer & the car), and an LCD display.  The interface
is built around a Sony "joystick" controller.  The primary function is
(you have probably guessed it by now) an MP3 player.  But I would also
like to integrate diagnostics, as well as having more fully-functional
diagnostics available from my laptop.

What work has been done at this point, and where is work needed?  Is
there a CVS tree set up anywhere?  If not, I would be willing to host
one.  What license will be used for this project?  I hope GPL.

What's this I hear about an alternative interface that doesn't use J/K?

Regards,

Jeff

Hi,

I have recently started work on a PC based scan tool: I wanted to build a
protocol converter (SAE to RS232) based on a PIC chip. The same could be
done using the Intersil HIP7020, but I wanted to keep the cost down.

I only had access to the SAE documentation, so I was not aware of the
fact that a 'ready made' standard serial mode is already implemented in
VWs. This can make life a whole lot easier - a voltage converter based on
the MAX200 chips would be very easy to make, and I could skip the protocol
converter stage and could start on the data gathering and display software
straight away. The standard status/control/diagnostic code sequence definitions
are in the SAE documents and most of those are likely to apply to VW as well.

What would be helpful though:

> RTS is hooked up (thru a level converter) to the L line & "wakes up" the
> ECU @ 5 baud or something. ISO 9141-2 also says you need to talk @ 5bps
> on the L line to start communication, but VWTool seems to use the VAG
> custom protocol, not ISO otherwise.
Info on the start-up sequence, i.e. how the protocol type is selected. I have
not seen the ISO documents, so I would be interested to know what's in them
regarding this.

Any info on this 9600 bps VW protocol. If nobody has that info I suppose
we will have to find out from the traces...

> unless VW will give us a list of keywords & their numbers
There is probably a bit more to it than just a list of code-description pairs,
but if anyone has any info on VW specific OBD sequences, please share it ;-).

Any other thoughts?

Cheers

John

Hi,

I'm a grad student at UC Berkeley w/a '95 Passat (OBD-I).  This
project sounds pretty interesting.  I like to do my own repairs, so I
get especially frustrated when an auto manufacturer makes certain
repairs difficult or altogether inaccessible w/o equipment that's
impractical for a private individual to purchase.

I'm not real sure what resources the project is in need of at the
moment.  My background is in embedded control of mechanical systems.
So, I've some experience w/digital & analog design (more digital than
analog) & software for embedded control applications.

-ted