0411PCM - OBd2 dual devices

[evilstuie]

Hi All,

I'm wanting to run my gauges via OBD2 using DashCommand on an Android tablet, but also wanted to have a Heads Up Display running off OBD2.

Is this at all possible?

As I understand it it is possible but not stable, as VPW does not identify the source of the request, so all requests will have the PID responses received by all devices.
But given these devices would be requesting similar data I was hoping it would either be possible, or to identify which requests were being sent by what devices and then build an Arduino "filter" of sorts, so have the devices run through the arduino to send all requests, and when the responses come back go back through the arduino which then sends the information back to the devices on a separate output for each.

Would that work, or is there an easier option?

[antus]

I dont see why not. Actually VPW is OBD2 and OBD2 is designed to have multiple devices on the bus. I dont see that there would be a problem plugging them in and using a Y cable. If you have control over one of the devices, you can easily set a different ID to the dash. Say the dash uses F0 which is the first tool address, then the next device uses F1. The range of addresses for such tools is officially, and the requests are sent to device $10 (ECU):

$F0-$FD Off-Board Testers/Diagnostic scan tools

Having said that different flash tools use F0 and F1, and so maybe you could go F8 and F9 to pick something a bit less common.

You could probably do it with an arduino but the hardware would get a bit messy. Advantage would be you could reduce lag by reducing the traffic to the ECU by 50% compared to both tools requesting the same data. Lag is a bit of a problem to run a dash with VPW. Its OK but its not a fast protocol compared to reading can messages broadcast on the bus natively in more modern cars.

[evilstuie]

I dont see why not. Actually VPW is OBD2 and OBD2 is designed to have multiple devices on the bus. I dont see that there would be a problem plugging them in and using a Y cable. If you have control over one of the devices, you can easily set a different ID to the dash. Say the dash uses F0 which is the first tool address, then the next device uses F1. The range of addresses for such tools is officially, and the requests are sent to device $10 (ECU):

$F0-$FD Off-Board Testers/Diagnostic scan tools

Having said that different flash tools use F0 and F1, and so maybe you could go F8 and F9 to pick something a bit less common.

You could probably do it with an arduino but the hardware would get a bit messy. Advantage would be you could reduce lag by reducing the traffic to the ECU by 50% compared to both tools requesting the same data. Lag is a bit of a problem to run a dash with VPW. Its OK but its not a fast protocol compared to reading can messages broadcast on the bus natively in more modern cars.

The bulk of the car's wiring is from a VY LS1 including BCM, I just sick and tired of all the random OBD2 error messages from ABS, SRS and the trip computer not working.

I thought VPW couldn't use identifiers, only CAN Low and CAN high?

[antus]

VPW is an OBD2 compliant bus designed to have many modules on the vehicle bus. You can see more about it here: http://www.fastfieros.com/tech/vpw_comm ... otocol.htm There are threads about reconfiguring the VY cluster too, you can turn most of those errors of if you have the right software. I don't know the specifics though, search the forums and have a read.

[evilstuie]

VPW is an OBD2 compliant bus designed to have many modules on the vehicle bus. You can see more about it here: http://www.fastfieros.com/tech/vpw_comm ... otocol.htm There are threads about reconfiguring the VY cluster too, you can turn most of those errors of if you have the right software. I don't know the specifics though, search the forums and have a read.

Yeah the ABS doesn't have anything you can turn off, same with traction control.

It's funny, everywhere I read and anyone dealing with OBD2 devices says you can't run 2 at the same time, even with a splitter, but based on the link you sent, you can set an identifier for source device and recipient device.

I'm guessing the ID for most purchased devices is always configured to F0 / F1 for display devices so 2 display devices would likely conflict yes?

[Tazzi]

Yeah the ABS doesn't have anything you can turn off, same with traction control.

It's funny, everywhere I read and anyone dealing with OBD2 devices says you can't run 2 at the same time, even with a splitter, but based on the link you sent, you can set an identifier for source device and recipient device.

I'm guessing the ID for most purchased devices is always configured to F0 / F1 for display devices so 2 display devices would likely conflict yes?

There were VYs that came without ABS/TC, so the programming setting is there. Unfortunately after the entire time I have been programming those cars, I still havent had to supply for a vehicle without it thus haven't even needed to work it out. I know the cars exist since I had a mate that had one. Even had the manual handle wind up doors which I didn't know VYs could come with either!

With OBD2 devices, if the tool that is requesting the information from the ECU is using a different ID to the other tool, and then only looks for a response that matches its ID.. then it will work.

And example of two frames from two scantools requesting SAE live data from the engine computer could look like:
6C 10 F1 01 0C
6C 10 F2 01 0C

The engine computer will respond (where xx yy is the response data):
6C F1 10 41 XX YY
6C F2 10 41 XX YY

So long as the tools look for a response to their own unique ID, then there should not be any conflict.

[MudDuck514]

I have a ScanGaugeII OBD reader connected full time in my car showing 4 values.
It is my understanding that two (or more) of the SGII devices can be "Daisy chained" together to allow more information to be displayed.
That being said, it would be nice to be able to ALSO run a tablet with TorquePro to show OTHER things as well.

Mike

[antus]

Yeah the ABS doesn't have anything you can turn off, same with traction control.

I have this screen shot in my collection from the aapl vy dash tool. It shows the setting is there. Unfortunately the software is a leak, I don't have it, nor can I tell you where to get it. But you could try searching yourself. I think traction control is implemented with wheel speed data from the ABS, so I believe it would be the same code. Not my area of expertise though.

[evilstuie]

Yeah I've tried my best to find that software but can't.
It looks like the safest bet is to move forward and away from the VY gauge cluster and try and get my dash look less commodore and more KITT anyway.

Thanks Tazzi and Antus for the info.
I think I'll install it as is with the 3 way splitter and switches and if I have issues I can turn the other devices off until I build something to intercept the requests, edit the identifier, then send it, intercept the response, edit it back and resend to isolated data channels through an arduino or something.
I haven't looked into the timings or hardware, but I suppose anything can be done with enough time and effort.

[antus]

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