GM Can to ALDL

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Re: GM Can to ALDL

Postby Tre-Cool » Sun Jan 22, 2023 1:06 am

the issue is the can gateway in the vz only works with the earlier can protocol. so using early tcm/ecu will likely talk to the abs module & dash fine.

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Re: GM Can to ALDL

Postby ben_att » Sun Jan 22, 2023 9:52 am

This is true, however I can’t find a VZ OS that will communicate and control the 6l80, my VF’s with the 6l80 are so much better to drive and so much more responsive than the old 4l60 which is why I don’t want to go back to the VZ software. I can drive the VZ I’m playing with now and although I have no Speedo or tacho, it is so much better to drive than the 6L crewman with a 4 speed. Additionally the motor I put in is the L77, I don’t think any of the VZ’s came out with any of the DOD or flex fuel etc either which is another reason I wanted to keep it running on the VF ECU.
I found another thread last night on here where there is someone who developed a BCM/PCM simulator and someone was asking similar questions to what I’m trying to do, so at least I’m not the only one :lol:

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Re: GM Can to ALDL

Postby antus » Sun Jan 22, 2023 10:00 am

I think making some version of your own pim might work. the hardest part would be getting the timing right and syncing your transmission on the ALDL bus which is very busy without a collision on the ALDL side. You might need to shoot for the gap that logging software uses to silence the chatter, and if you transmit in that gap the you will probably loose the ability to log. I think the pro micro and MCP 2515 might be fast enough to keep up. You can look at the docs for the auto_wp can library and see if you can implement a filter in the MCP 2515 to take load of the pro micro cpu. The cool thing about the pro micro is it has native usb for the pc side when your developing and a hardware uart which helps a lot with reliable aldl. It seems to do 8192 baud fine. I had a lot of trouble with software serial implementations before I settled on the pro micro hardware. The software solutions say they cant transmit and receive at the same time, which is exactly what aldl echo looks like. Some people seem to have gotten it to work, but I not me. There is also the esp32 hardware which has uarts and can, but you still need to add a can transceiver between the esp32 and the can bus. pro micro + mcp 2515 ticks the boxes easy, though. You might also be able to have your own aldl bus just between the pro-micro and the dash, to avoid bus collisions and allow the vehicle bus to function normally.
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: GM Can to ALDL

Postby Tre-Cool » Sun Jan 22, 2023 11:12 pm

ben_att wrote:This is true, however I can’t find a VZ OS that will communicate and control the 6l80, my VF’s with the 6l80 are so much better to drive and so much more responsive than the old 4l60 which is why I don’t want to go back to the VZ software. I can drive the VZ I’m playing with now and although I have no Speedo or tacho, it is so much better to drive than the 6L crewman with a 4 speed. Additionally the motor I put in is the L77, I don’t think any of the VZ’s came out with any of the DOD or flex fuel etc either which is another reason I wanted to keep it running on the VF ECU.
I found another thread last night on here where there is someone who developed a BCM/PCM simulator and someone was asking similar questions to what I’m trying to do, so at least I’m not the only one :lol:


yeah what you would need is to convert late can to early can & back for abs, along with can to aldl for the dash cluster.

i got lucky with the vy as the abs pretty much works standalone just fine with no input from anything.

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Re: GM Can to ALDL

Postby Madchuska » Tue Jan 31, 2023 12:24 am

antus wrote:Completely unrelated I built a 5v arduino pro micro + mcp 2515 to try and do aldl to can (rather than the other way around) for a can data logger to work on 12P. I got it working on the bench properly, then it kinda stalled and thats where its sitting. The speed is pretty slow, though its hard to tell if thats more in the elm clone I was using to test it, or the pc software. In theory it should be able to handle 5-8 60 byte ALDL frames a second on the aldl side, and plenty of requests on the can side. In practice I think the issues were pc app + elm, not the board I built. Can share more details if you want a starting point to build your own tool for your purpose, though you can see what the hardware should look like from the code, which I have attached.



This is great, I started going down a similar path and was doing some basic testing in the car but it never really went any further.

At first I was trying to pick-up the CCM A/C request frame in a VX then transmit via CAN to my Aftermarket PCM. - I was able to get this side to work.

The Aftermarket PCM also transmits the A/C Status via CAN so I wanted to receive this and then transmit it via ALDL in the 41 broadcast frame so the CCM knew that the A/C was enabled. (this seems allow you to use the "Auto" function on the CCM module - Yes I know its a silly want...) I have a feeling that the CCM also wants the A/C pressure for some reason this is also transmitted by the Aftermarket PCM is is possible.

Another one in the 41 broadcast frame is Low Speed Fan Control so If the above is possible to get working I was also hoping to do this.

The last 2 points is where I got stuck, The PIM is still connected via ALDL but not receiving anything on the ECU side so in my case it seems to almost be transmitting random data.
An alternate idea was to have a CAN to Class2 module but this seemed to be harder to find info on and I don't have the tools to sniff it.

At this point in time I think the only reason the PIM is there is because from memory the car wouldn't start without it. I could possibly just wire the Start wire to the aftermarket PCM and remove the PIM all together.

Any suggestions on what else the PIM could be doing?
Am I one the right track with the ALDL side or would you look to use a different PIM or the Class2 option?

Thanks in advance

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