Sending a can message on GMLAN

[ntrambitas12]

Hi,
I stumbled across this library while looking for an interface to write a simple program to send messages on the GMLAN. My car is a 2014 Cadillac ELR. I have a packet that I want to try to send. I was told that the following message is correct to send (it commands the windows to roll down) but as I connect to the network and try to send, nothing happens and an exception is thrown. Am I not correctly setting up my connection to the GMLAN or formatting the CAN message correctly?

Thank you for any help!

[BrianHumlicek]

I have never used GM LAN, but doing some reading, it appears its 29bit CAN among other things. At the very least, you will probably need to use the 29bit flags on connection and on each message transmission. This is assuming that using the CAN protocol is appropriate for GM LAN. I suspect there might be another protocol definition that is intended to be used for that, but I don't know.

Brian

[BrianHumlicek]

Doing some reading, it appears you should be looking at one of the SW_CAN protocols. SW_CAN_PS I suspect is the right one. Also, I just added a baud definition for GM LAN. It might take a minute to get nuget updated though.

[BrianHumlicek]

All of the protocols with the _PS suffix are ‘pin switched’ protocols, meaning the physical pins it originates from is not defined in the specification. It needs to be configured with the connection.

This is j2534-2’s solution to adding more physical layer protocols than we have physical pins for. It allows the user to pick and choose what physical layer configuration is needed.

Brian

[ntrambitas12]

Hey Brian, I've tried the change you mentioned but now it throws an exception as soon as I run the change pin command. It's "Error creating ComLogicalLink"

This is the code I have:

Any clues?

Thanks again for all your help,
Nick

[BrianHumlicek]

I'm not sure. My only suggestion would be to remove the line that opens 'channel1' as maybe its conflicting with the GMLAN channel? Alternately, its possible that your device doesn't support running that protocol on that pin. Again, I'm not really sure, GMLAN isn't something I have experience with.

Brian

[ntrambitas12]

Hey Brian,

I finally had some more time to poke around. So I have a feeling that I am just not setting the Pin correctly. I know for sure that my passThru is compatible with GMLAN since I used it before to reprogram GMLAN modules. GMLAN is on pin 1. I tried passing in 0x01 and just 1 and I get this exception. I tried commenting out the HSCAN channel and the same thing. I think its something related to the way Im trying to set the pins.

I feel like its so close to working

Thanks,
Nick

[BrianHumlicek]

I’ve been there before myself. For me it has been a combination of connect and txflags. In the past I have used the debug mode built into Drewtechs API to sniff a known working implementation and then do what it did. I’m not sure if tour device has anything similar.

If your device doesn’t have any thing similar, I think I may have seen a piece of software on GitHub that might do something similar. I never used it so I don’t know for sure, but I’ll see if I can find it and link it.

Brian