capture/repeat data ?

[Sam]

I'm going to order the chip:http://www.scantool.net/products/pro...&products_id=8

And I'll make the pcb myself with this: ElmScan VPW Schematic/PCB 1.0/A

And then use their s/w if you think I need anything else, please advise.

I'm going to mainly use this with a 2003 Chevy Avalanche so I hope that it is the vpw that I need. I was really hoping to record the actual data from the vehicle in serial form which I think you are saying this will do it, and prog that data into the PIC and have the PIC TX it with SEROUT.Would I still need the ELM chip in the circuit in order for this to communicate with the data bus ?

The actual data I refer to is say,what is produced on the data bus only when one button is pushed. Is all this reasonable?

Thanks again!

[DynamoBen]

You will need to use the 2.0 PCB, not 1.0.
NOTE: the schematic uses a 9.1V transistor, which could be difficult to find.

http://www.scantool.net/download/elmvpw20.pdf

You can check your vehicle to find out what data type it uses with the following link:

http://www.elmelectronics.com/obdstandard.html

On the ELM322 there is a mode called "Monitor All." Launch hyperterm and turn this mode on. Then hit the buttons you are interested in; any data on the line will show up in hyperterm.

Once you have that info that should give you an idea of what a packet looks like. There are a couple of things about the packet you need to know, for example addressing scheme of the packets. (physical or functional) I can help once you have an example of a data packet.

It would be worthwhile to grab the datasheet for the ELM322, and read it through. It’s written with hobbyists in mind and talks about all the different ways the chip can be configured. Its geared toward reading the cars ECU but you can read between the lines.

Will this work? It’s hard to say for sure until you have captured a packet. I think it should work fine; it will however take some creativity on your behalf. You don't need the chip to communicate on the buss, but it will make it a lot easier. If you don't use the chip your pic will need to deal with all the timing parameters for VPW and the CRC encoding and decoding. (not fun...not easy!)

[DynamoBen]

Here is the ELM322 board that I built based on their schematic and PCB.

Two things to note:

First is that I used a DB9 instead of the DB25. (personal choice)
Second I built a DB9-->Clips adapter for testing. You may want to do the same. (all Radio Shack parts)

If you want to use it for automotive diagnostics you will need to order the cable from scantool.net when you order the chip.

[Sam]

OK,
I downloaded the 2.0 sch. and will build that while the elm 322 chip is on its' way. The 9.1 transistor you refer to,did you mean the 9.1v zener (D3 1N5239)? I think I already have one of those and I know I have all the other parts on hand. I will order their obd cable.

Good pics,thanks, that's what I'm going to do.

"On the ELM322 there is a mode called "Monitor All." Launch hyperterm and turn this mode on. Then hit the buttons you are interested in; any data on the line will show up in hyperterm. "

That, I think, is basically what I did with the Fogsoft program this morning but I didn't understand the output from it. It's on the other old laptop and I'll post it here later on.

I'll get the data sheets and start studying them. Thanks, this is all vey much appreciated ! I can't wait to get this working.

[DynamoBen]

Once you get it assembled post a string and I will do my best to decypher it for you.

BTW if you ever decide to go with the ELM327 the ELM website has the PCB and schematic for that board, scantool doesn't.

[Sam]

Hi, here is the email I sent to elm.....
--------------------------------------------------------------------------

I'm very interested in purchasing your products, mainly to start with, the elm322.
My question is, with your product can I record a specific section of data from the vehicle, for example, window down, and then be able to re-transmit that section of data back to the vehicle to perform the window down function ?

Thank you for any information on this
--------------------------------------------------------------------------

Here is what elm says...
--------------------------------------------------------------------------
Hello:
Thank you for your interest in our products. Sorry, but our OBD ICs can not do that for you.


J. Nagy
Elm Electronics
--------------------------------------------------------------------------


Maybe I didn't word things right to them or do their chips communicate with the ecm on something other than class II ? What do you think about this ?

[DynamoBen]

That is not the original intention of the device; so he is correct. However I know your application and I think it will work. I also know Jim (J Nagy) very well; he created the chips and is the owner of the company. He and I are in contact quite a bit.

I think the issue is how the email reads. Most times window up/down is electrical; not data. In your case its data, assuming it is VPW this device should work great.

Remember, worst case, if it doesn't work and you have diagnostics device for your vehicle.

I emailed Jim some of the back-story for clarification. He likes to hear about new uses for his chips.