J1850 VPW Sniffer

[jlvaldez]

Hey guys. I'm trying to sniff my VPW bus on my corvette. From what I can gather, the J2534 tools don't sniff, but do allow you to read/write.

I'm trying to find something that that I can plug into OBDII and sniff/write data if I want. I've made a datalogger for CAN, and was hoping to avoid the software work to write a VPW to UART library on a microcontroller.

Does such a tool exist that's affordable for the hobbyist?

I'm in the middle of schematics on a small board with a MCU and a discrete front end for the VPW interface, connecting to a HC05 to get serial over bluetooth. Pretty simple and specific tool. Most of the work will be in the firmware for it. Before I pull the trigger and start layout on this board, i'm curious if any such tool exists.

If I have to write it, I plan to avoid an ELM because they seem to only support 1x VPW mode, and I'd like to support 4x. The downside is that all of this needs to be done via software (no hardware VPW modules in MCUs from what I've seen), which can be done, i'm just going with an overkill MCU. I can support AT commands with a higher baud rate port, but I generally like avoiding ASCII communication, since it is SUCH a waste of bandwidth on the serial port, which is already slow.

Most of my previous projects, I use a serial protocol and have to write some software to handle the interpretation of data, but I guess AT commands could be used with higher speed baud. 112500 might be sufficient....

[jlvaldez]

Stumbled across the AllPro. Hard to tell for sure, but it looks like it supports VPW 4x using standard AT commands over a comm port, which would be easy.
https://www.obddiag.net/allpro.html

There's also a kit, which has a DB9 connector over the horizontal 100 mil headers http://www.obddiag.net/allpro-kit.html

Can't find a source to buy it, but I can send it off to be fabbed and assembled. Question is if it's able to monitor the bus? Quick look at ELM AT commands suggests this is possible.

[In-Tech]

I've briefly looked around for a hobbyist j1850 pwm and vpw sniffer too. At this point I will have to do a lot more reading before I can attempt to make my own.

[jlvaldez]

Well, I just spent the better part of 2 hours trying to quote a build on the allpro.... They supplied no BOM from what I can see. There's an eagle source doc, but I am using kicad, and it seems to barf trying to import...

I could get the gerbers uploaded and quoted, but my issue is that I cannot find a list of components required for assembly

Frustrating... I've been trying to take my best guess looking at the only schematic supplied.

[In-Tech]

I think quite a few people here have those AllPro's. Maybe somebody can snap a pic of the populated board/components.

[jlvaldez]

Well I was able to build what I assume is a correct bom list for it. Placed an order for the components. Sadly the minimum order is 5 boards, and components also had minimum limits to get better rates. Several components are currently obsoleted so I took my best guess at a replacement. We'll see. If I did it right, I guess I'll have 4 extra all pros that I would sell for cheap.

[In-Tech]

I like gadgets, I'll take one, pm me info and I can paypal or whatever.

[antus]

The OBD Xpro can sniff the bus with just a few commands to put it in the right mode https://obdxpro.com/product/obdx-pro-vt/

Code: Select all

ATSP2            # Protocol 2 VPW
ATH1             # Turn headers on
ATSH6C10F0  # Set the header to priority 6C to PCM 10 from Tool F0 (not entirely relevant for just logging)
DXPT1           # Enable pass through mode (turns on logging)
DXSMFF0000 # Sets the mask so that it only needs to match 6C (I think you can use 00 00 00 for all data, not sure as I didnt use that when I was logging with it)
DXSV1          # Sets VPW speed 1x or can use 4 to log at 4x

[In-Tech]

Hiya antus,
I bought one of those when they first came out to support you guys, and it IS a cool new gadget I didn't see anywhere on the site for software, think it said something about it being on the OBDX forum but that doesn't exist yet either.

[Tazzi]

Hiya antus,
I bought one of those when they first came out to support you guys, and it IS a cool new gadget I didn't see anywhere on the site for software, think it said something about it being on the OBDX forum but that doesn't exist yet either.

The forum was removed as it was getting flooded with spam, and nothing we implemented was helping prevent it or even slightly slow it down.