CAN Bus Interpretation

[gpeterson]

Originally Posted by lkv0315

So what exactly do you mean by terminated?

There are 120 ohm termination resistors at each end of the bus, see https://www.kmpdrivetrain.com/paddle...-tips-can-bus/. I believe the E53 has them at the cluster and DSC.

[gpeterson]

Originally Posted by lkv0315

I’m using a CAN HAT called the waveshare RS485

I posted saying that won't work then I read about it. The name is deceiving - RS485 is not the same as CAN, but looks like that device does both.

[80stech]

I don't think the BMW CAN bus uses RS485 which could be part of your problem. RS485 is directional so the software will need to take that into account. Almost anything can be made to work but you might be best off to get a specific CAN bus module.

[lkv0315]

Originally Posted by 80stech

I don't think the BMW CAN bus uses RS485 which could be part of your problem. RS485 is directional so the software will need to take that into account. Almost anything can be made to work but you might be best off to get a specific CAN bus module.

So do you think a module with this kind of specifications is more appropriate?
https://www.amazon.com/dp/B087PWBFV8...TQB2EDBKT15SPK

[80stech]

I'm more of an Arduino guy, but yes, and that's probably even overkill but nice to have the isolation and for sure the voltage transition since I think the Pi is 3.3v. You should maybe make sure of the voltage that the X5 uses on the CANbus. Is there maybe a sketch to use the Pi as a logic analyzer ??

[lkv0315]

Originally Posted by 80stech

I'm more of an Arduino guy, but yes, and that's probably even overkill but nice to have the isolation and for sure the voltage transition since I think the Pi is 3.3v. You should maybe make sure of the voltage that the X5 uses on the CANbus. Is there maybe a sketch to use the Pi as a logic analyzer ??

Not sure about the second part, but I’ll look. I can only find it in a 2 channel variation, which I thought would be nice but I can’t terminate the bus so I wouldn’t be able to connect the engine and trans systems separately.

[80stech]

There is no need to terminate the bus ?? Should be no reason you can't read both channels.

[gpeterson]

The board you have is fine despite its misleading name. It has a MCP2515 CAN transceiver which I'm familiar with and have used in some BMW CAN projects of my own.

No need to worry about Pi GPIO voltage since that has nothing to do with the CAN bus voltage.

There is also little likelihood that you need to tap into the dedicated DME <-> AGS bus as well. What values are you looking to read and use in your display? I can probably help with that.

[gpeterson]

Originally Posted by 80stech

There is no need to terminate the bus ??

No, it is already terminated at each end or else it wouldn't work. If you add another device that has a termination resistor it will likely disrupt existing bus communication.

[lkv0315]

Originally Posted by gpeterson

The board you have is fine despite its misleading name. It has a MCP2515 CAN transceiver which I'm familiar with and have used in some BMW CAN projects of my own.

No need to worry about Pi GPIO voltage since that has nothing to do with the CAN bus voltage.

There is also little likelihood that you need to tap into the dedicated DME <-> AGS bus as well. What values are you looking to read and use in your display? I can probably help with that.

So the RS458 board I talked about first will be okay? And that is good to know about the voltages. I’m looking to retrieve coolant temp (as a value), oil temp, mpg, AFR and throttle pos