Arduino based PIM

Ecu Hardware Modifications
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Re: Arduino based PIM

Postby megajuz3003 » Tue Jun 23, 2020 2:22 pm

Resurecting this thread, dug this project out for a bit to try and make some progress and i am looking for a little info

I have broken down a good part of the 41 Frame but i have found 2 different lengths
Type 1 - 41,63,00,00,00,79,44,00,00,04,30,00,00,00,11,0C,4E
Type 2 - 41,68,12,00,76,34,78,41,AF,22,40,98,23,12,25,10,00,00,00,00,00,CF

from the vehicles ive tested the short frame is used on VT/VX V6/5l and the long frame used on VT/VX LS and all VY/VZ, but im not sure.. can anyone shed some light on this as im assuming if i use the longer frame it should work on all VT-VZ so long as it formatted correctly

also for the ecu communications, i dont have much access to OBDII PCMs for testing but i was hoping a few people wouldnt mind posting up some short logs of thier CAN/J1850 data bus so i can try and breakdown any broadcast data like Tazzi suggested instead of polling pids for data

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Re: Arduino based PIM

Postby Tazzi » Tue Jun 23, 2020 3:24 pm

My LS1 P01 and L59 basically send nothing when sitting their idle.. although that might be due to having no PIM connected.
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Re: Arduino based PIM

Postby megajuz3003 » Tue Jun 23, 2020 4:16 pm

Tazzi wrote:My LS1 P01 and L59 basically send nothing when sitting their idle.. although that might be due to having no PIM connected.



this is something that i was concerned about, the PCM might have to be prompted to broadcast data, if this is the case it might not be too easy to rely on broadcast data as i would assume each PCM would probably have a different request for it :hmm:

the other option would be just to poll the PIDs but i would have to work out how long a cycle would take and possibly only update specific params (lower priority) every second third or fourth cycle if needed

i think the 41 Frame is requested every 128ms so things like Speed, RPM IAT, Temp etc would be updated every time but things like Gear Selector, AC pressure (if readable) CEL , ect might get updated on alternating broadcast cycles.....

unless you have a better idea

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Re: Arduino based PIM

Postby antus » Tue Jun 23, 2020 8:43 pm

I wouldnt expect the pids to change, they are standardised. Both SAE and Proprietary, but still standard.
Have you read the FAQ? For lots of information and links to significant threads see here: viewtopic.php?f=7&t=1396

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Re: Arduino based PIM

Postby pman92 » Tue Jun 23, 2020 10:05 pm

I've been playing with VPW lately with the intention of turning my BCM simulator into a BCM and PIM simulator.

I believe all VT/VX would have the shorter 41 frame. I've got some VT Pims here so I'll confirm when I get a chance.

I can confirm most of the data from the VPW PCM is requested by the PIM, it doesn't just broadcast it out. It's virtually all functional VPW frames as defined in J2178-4.

I only just got a complete Vpw data log with a PIM/PCM on the bench the other day (hence my post earlier this week about what all the functional addressed messages were). I haven't gone through it yet but from a brief look you can see the PIM requests for things like RPM and gear position and the PCM responses. I'll post it up in the morning if you want to go through it.

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Re: Arduino based PIM

Postby pman92 » Wed Jun 24, 2020 8:11 am

I've just confirmed the VT PIM I have here outputs a "41 63" ALDL message (not the 68 length like VY/VZ).

I've attached the quick data log I did on the bench showing the first 5 seconds of VPW activity. Its very busy in the first second after ignition on.

See picvrss's reply to my question last week and what you see in the data log will make sense: viewtopic.php?f=42&t=6799

On another note does anyone now what the messages with destination/primary ID "EA" and "EB" are?
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Re: Arduino based PIM

Postby Tazzi » Wed Jun 24, 2020 9:40 am

pman92 wrote:I've just confirmed the VT PIM I have here outputs a "41 63" ALDL message (not the 68 length like VY/VZ).

I've attached the quick data log I did on the bench showing the first 5 seconds of VPW activity. Its very busy in the first second after ignition on.

See picvrss's reply to my question last week and what you see in the data log will make sense: viewtopic.php?f=42&t=6799

On another note does anyone now what the messages with destination/primary ID "EA" and "EB" are?


EA/EB is to and from ECU off the top of my head.

ELMs have the default header so to that.

What are you using for the VPW side of communciation?
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Re: Arduino based PIM

Postby In-Tech » Wed Jun 24, 2020 10:04 am

Hi, sorry to interrupt. What are you guys using for a j1850 datalogger? I glanced at the 5 seconds pdf and that looks nice.

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Re: Arduino based PIM

Postby megajuz3003 » Wed Jun 24, 2020 11:23 am

pman92 wrote:I've just confirmed the VT PIM I have here outputs a "41 63" ALDL message (not the 68 length like VY/VZ).


ive just been going through my raw logs here and all bar one VT/VX PCM/PIM uses the "41 63" Frame so i think the single one i have that uses the 68 might have a VY pim :wtf: for the sake of keeping things simple ill dig out my VT/X test bench and see if the cluster is happy with a 68 len frame, if it is that will make things easier


pman92 wrote:I've attached the quick data log I did on the bench showing the first 5 seconds of VPW activity. Its very busy in the first second after ignition on.

See picvrss's reply to my question last week and what you see in the data log will make sense: viewtopic.php?f=42&t=6799

On another note does anyone now what the messages with destination/primary ID "EA" and "EB" are?


thanks alot for that im hoping to make some headway here with working out the best and most efficent way to get the data from the ecu, have to get my hands on a few ecus so i can start playing with them, what software are you using to log, the output looks nicer than my copy and paste job from the VX Daig included software

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Re: Arduino based PIM

Postby pman92 » Wed Jun 24, 2020 11:40 am

Im using a mega328 on a breadboard that I've programmed to read (and eventually transmit) VPW. It uses a pin change interrupt and timer1 and will eventually use a timer output compare interrupt for writing the transmit pin. I've taken some inspiration from the arduino code in the PCMhammer repo but it's somewhat different. The hardware interface just uses a comparator to check VPW voltage and interface the 0-7.2v VPW to 0-5v atmega voltage.
The atmega328 spits out the time of receive in milliseconds and all the data in CSV format.
Then I just copy the data from the terminal window and save it as a CSV file (or use putty to save the terminal session to a CSV automatically).
Then I've got a spreadsheet that I import the data into, and it puts it all in the nice table so it's easy to read.
I'll post up the spreadsheet tonight
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