Software On ELM Street - OBD2 Software Development

[Tazzi]

Decided I needed to open an ELM unit to get some measurements of tge case and PCB board.

These elms are a bit more expensive, PCB seems to be good quality.
Found it interesting it uses a NXP TJA1040 CAN transceiver. Thought they used a MCP2551.

The cases are actually cealed along the sides.. looks like they actually tack melt the plastic on the sides. No screws are used on the top.

I actually nicked the board slightly along the mid right edge.. hoping I didnt cut into the copper lines. Wont know till I power it up again, hopefully it didnt ruin VPW or CAN. The other protocols can get stuffed

Anyways. I grabbed the dimensions of the PCB incase anyone is interested or wants them.

(Sorry poor image quality.. iphone camera seems to be getting worse!)

082.JPG (2.73 MiB) Viewed 5696 times

[Dylan]

Looking to make your own?

[Tazzi]

Looking to make your own?

Something like that. Add some abilities for the VE commdores

Have to update the size and holes to suit the ELM case. And a few other minor alterations to the schematic.. but should be read to go.

NewBoard.PNG (42.78 KiB) Viewed 5683 times

Or alternatively, modifying the originally ELM design (well.. the boards I get) to get single wire communication going. But.. this will remove the ability for dual wire. Id hav to move to a dedicated elm chip like the ELM329 to have both dual and single wire going. And even then, the ELM329 chip by it self is $22usd! But, at least it is an option.

[Dylan]

Signe me up. Just brought a VZ with LS1. Completely new to these things always avoided all late model talk.
Been looking at them but don't know who's got the good one's.

Pretty keen to tune it got your own tuning software yet? LOL

[antus]

That looks like a decent elm in that it includes the pic 5 pin programming header down the bottom. You can hook up a pickit2 or pickit3 and flash your own firmware straight on to it via that header if you wanted to experiment with that. Still, flogging a dead horse really.... your design looks more the go, and without the elm limitations

[Tazzi]

Sign me up. Just brought a VZ with LS1. Completely new to these things always avoided all late model talk.
Been looking at them but don't know who's got the good one's.

Pretty keen to tune it got your own tuning software yet? LOL

Well, all depends if it all works! Im checked, double checked, triple checked and even contacted the developers to verify. So, hopefully the first revision will work straight out.
LS1 is on VPW. I *currently* havent added that section in on the above board. I wanted to make sure I had room for it after the CAN stuff was added. Since there is 3 separate can transceivers on the board. GMLAN, MS CAN and Standard CAN.
If the VPW components fit on the board and I can get it to all route properly, then I will be going with that.

That looks like a decent elm in that it includes the pic 5 pin programming header down the bottom. You can hook up a pickit2 or pickit3 and flash your own firmware straight on to it via that header if you wanted to experiment with that. Still, flogging a dead horse really.... your design looks more the go, and without the elm limitations

I saw that. Nice little header to get on. But Im not too sure on programming a PIC, let alone finding suitable CAN and VPW routines. Iv got the VPW routine down I think, but would have to research some CAN routines, or port some over.
Would also require either sticking with the ELM format with strings ect. Or make my own... where the AVT protocol would be more suitable to follow.. just more work!

[Tazzi]

Stupid VPW circuit has been made way more complex then it really needs to be. The recommended part isnt even in stock on digikey!

Will see what happens.. not to hopeful on vpw working though.


hmmm... Id assume I could copy the ELM327 vpw setup.. id assume that would work fine...
Dont really need a compactor.. just need to use transistors I believe.... bugger it, Ill use the ELM327 vpw design

*Edit
After adding in the VPW hardware, required vias went from 40, to 220... A bit of rearranging is in order..

[Tazzi]

I honestly... cannot get it to fit using to current parts sizes. I will have to go even smaller for part size.. this shall be interesting..

[antus]

Have you gone double sided already?

[Tazzi]

Have you gone double sided already?

Iv got the space, but its the actual traces that I cant get to fit 100%

I can make it work fine using traces only. But I always make the top layer as a ground sink, and after the tracing has finished and it finalizes with the grounding top layer.. it always has at least one pin cut off from the other grounds!