CAN Bus Interpretation

[Thaniel]

Baud rate for the PT-CAN bus (only CAN bus in an E53, I expect) is 500k.



What do the wires you connected to attach to?


CAN bus wires are twisted pair. For the E46 and similar vehicles (probably E53) it is yellow/brown and yellow/red or something very similar. Might be good to check a wiring diagram. It should clear it up. Careful with yellow wires as yellow is often used in airbag systems. Don't randomly try wires. Also CAN bus is 5V or less. Tapping a 12V wire could have bad consequences.


Make sure CAN H and CAN L are not reversed as well.

[lkv0315]

Originally Posted by Thaniel

Baud rate for the PT-CAN bus (only CAN bus in an E53, I expect) is 500k.



What do the wires you connected to attach to?


CAN bus wires are twisted pair. For the E46 and similar vehicles (probably E53) it is yellow/brown and yellow/red or something very similar. Might be good to check a wiring diagram. It should clear it up. Careful with yellow wires as yellow is often used in airbag systems. Don't randomly try wires. Also CAN bus is 5V or less. Tapping a 12V wire could have bad consequences.


Make sure CAN H and CAN L are not reversed as well.

I didn’t check the module, but it was the lowest module in the rack behind the glovebox. I assume the DME, since the plug looks just like the one in that pic. I grabbed those two wires, and a wiring diagram I’d consulted shows that it is yellowblk and yellowbrn as high/low respectively, which I did with red and black wires respectively. I also got nothing when I reversed the polarity on the can receiver. I will try a 500k baud in a bit!

[Thaniel]

Originally Posted by lkv0315

I didn’t check the module, but it was the lowest module in the rack behind the glovebox. I assume the DME

Curious what you have tapped into. Per the diagram shared on post 2 https://xoutpost.com/1209456-post2.html
CAN bus wires only goes between
KOMBI
DME
AGS
DSC
Steering angle sensor.

DME, AGS and DSC are under the hood.

WE are talking E53 right (not E70).?

[lkv0315]

Originally Posted by Thaniel

Curious what you have tapped into. Per the diagram shared on post 2 https://xoutpost.com/1209456-post2.html
CAN bus wires only goes between
KOMBI
DME
AGS
DSC
Steering angle sensor.

DME, AGS and DSC are under the hood.

WE are talking E53 right (not E70).?

Correct, E53. I will send a pic shortly if I can

[Clavurion]

Behind glovebox sounds like body module (GM3).

On GM3:
*Yellow/black - rear lid (bottom) unlocking
*Yellow/brown - drive rear lid (top)

[lkv0315]

Originally Posted by Clavurion

Behind glovebox sounds like body module (GM3).

On GM3:
*Yellow/black - rear lid (bottom) unlocking
*Yellow/brown - drive rear lid (top)

After a brief google search, that would be the one. Makes sense why it wasn’t doing anything hah.
Is there a cable grommet on the passenger side to pass wires thru to the cabin?

[gpeterson]

The CAN interface you are using has a termination resistor. That may be one of your problems.

https://www.waveshare.com/w/upload/1..._Schematic.pdf

You should look at WDS for pinouts before hooking things up.

[lkv0315]

Originally Posted by Thaniel

Baud rate for the PT-CAN bus (only CAN bus in an E53, I expect) is 500k.



What do the wires you connected to attach to?


CAN bus wires are twisted pair. For the E46 and similar vehicles (probably E53) it is yellow/brown and yellow/red or something very similar. Might be good to check a wiring diagram. It should clear it up. Careful with yellow wires as yellow is often used in airbag systems. Don't randomly try wires. Also CAN bus is 5V or less. Tapping a 12V wire could have bad consequences.


Make sure CAN H and CAN L are not reversed as well.

So after I was out of town for a week, I’m back to working on this. I tapped the twisted pair that run in accordance with that picture. I’m still not getting any data back. Would I have to physically de-pin the connector then essentially force the signal to go through the pi, by essentially removing the direct line between the two modules and put the PI in the middle? I’m not sure what else to try at this point other than a different CAN bus module.


Sent from my iPhone using Xoutpost.com

[80stech]

Are you running the display with a serial channel? Does the library for the canbus module have some test and diagnostic routines?

[lkv0315]

Originally Posted by 80stech

Are you running the display with a serial channel? Does the library for the canbus module have some test and diagnostic routines?

I’m not sure about the display, but it’s on the miniHDMI if that says anything. There are two test routines that display the raw data that’s coming in on the CAN lines, but I’m not sure about how to test if the setup is correct