Arduino based PIM

[megajuz3003]

A little while ago i posted about "Frankenstein's Monster" aka a Barra conversion on a VY SS that a mate of mine is doing

i'm heading down the path of creating a "PIM" using an arduino, as the ECU is standalone i dont think i need to do any security VATS/PATS linking or anything like that. just get the instrument cluster packet to the cluster

my inital thinking is to build both an STN1110n and ALDL interface so that the arduino can request the required data from the ECU on the STN1110n interface then generate the 41 cluster packet and broadcast it receives the 40 reqest from the BCM..

for the sake of clarity i was hoping someone could at least point me in the direction of 2 things.. i have the 40/41 broadcast packet pretty well documented but i cant find anything on the rest of the packets other than generally what they are and couriosity is bugging me to find out, also i would like to be able to poll the abs unit for a wheel speed - during testing (dont want to be polling a saftey module during normal opperation) unless this info is in the 90/91 broadcast packet where i can use it without polling the module directly

Random thought process of the schematic - more or less just trying to get my thoughs down to something, dont knock the whiteboard or the very bad schematic that definatley has bad/wrong symbols

IMG_1614_2.jpg (198.64 KiB) Viewed 16322 times

[j_ds_au]

Two thoughts/questions ...
1. What are the two transistors supposed to be doing?
2. Wheel speed is road speed, so shouldn't you read that from the PCM, rather than the ABS?

Joe.

[megajuz3003]

Two thoughts/questions ...
1. What are the two transistors supposed to be doing?
2. Wheel speed is road speed, so shouldn't you read that from the PCM, rather than the ABS?

Joe.

The transistors are probably drawn wrong but they are supply power for the circuit 5v and. 3.3v according to the atmeda and stn1110n schematics. I plan on drawing it properly when I find some time

I plan on pulling the speed from the ecu but I have concerns with conversion wiring. Apparently the conversion wiring has the speed input piggybacked from a wheel speed sensor, as there is no sensor on the gearbox, I’ll be sure on this when the harness comes back

[Gareth]

Following this topic with great interest, sorry I have nothing to add

[megajuz3003]

cannibalised a crappy china elm327, added aldl interface without the serial conversion for now just to try and get an idea of how to make it all talk lol


cant find much on aldl on Arduino and obd2 seems split down to individual protocols instead of a complete library but ive only been looking for 30 mins or so lol

[megajuz3003]

have a very crude idea of the processes I need to undertake software wise

Code: Select all

<Setup>
// PIM Constantly Powered ON when plugged in

	Verifiy ELM/STN Device
	Determine OBDII Protocol
	Set Protocol
	Set Vehicle (VT/VX or VY/VZ) // For Generating the UART 41 Frame 
	Verify GM-UART Datasteam
	
</Setup>

<Loop>

	If Ign = ON
		Read Required OBDII PIDS
		Generate UART Frame 41, XX
		
		Listen for UART Frame 40, XX
			Send UART Frame 41, XX
	
	else if Ign = OFF
		something here ?? 
	end if

</Loop>

[Tre-Cool]

I would be interested in commiting some dollars if you can get it work with with gm-can to aldl too.

I've run a late model e38 in my vy and got everything to work bar the coolant temp, i have the factory vz pim module in it, but it appears it doesnt like the later model e38 broadcast. it works fine with an 07 e38 though.

[megajuz3003]

I would be interested in commiting some dollars if you can get it work with with gm-can to aldl too.

I've run a late model e38 in my vy and got everything to work bar the coolant temp, i have the factory vz pim module in it, but it appears it doesnt like the later model e38 broadcast. it works fine with an 07 e38 though.

my plan is to try and get it to read everything from the standard "Generic PIDs" nothing manufacturer specific so hopefully so long as its CAN or J1850 it should work.. I don't see a need for the ISO protocol or really even J1850 but J1850-VPW is the only ECU I have handy to test with, my daily is a VU SS

also looks like I definitely need to use a Arduino Mega2560, for the native multiple serial support.. these aren't as cheap as Unos or Nanos

my OBD11 knowledge is very limited but it looks like I just have to send the right commands to the ST1110 and read the response, not all that different from GM-UART (ALDL) so it really just looks like making sure timings are good enough that I can do all the OBD11 communications and generate the 41 Frame in-between the requests for it

[pman92]

I'll post up a copy of the 2/3 transistor circuit I used to interface ALDL to the UART RX/TX lines. I have found it work's good and is probably better than joining them directly for various reasons.

If you want a smaller physical mega2560, look into a mega2560 pro embedded.
They are like a mini Arduino Mega.
Like $10 on aliexpress

[pman92]

Also looking at this:
https://www.fueleconomysolutions.com.au ... australia/

It will need to be a series 2 BA to be OBD2 compliant so you can use generic PIDS (OBD2 wasn't mandated in Australia, the first OBD2 commodore was VZ).

EDIT: I could well be wrong but I would be checking it is actually OBD2