Does anyone know how I can find out some details on the W211 Canbus protocol? I need to know some details on the message formats and contents specifically relating to the steering wheel audio and phone controls. I'm considering buidling an interface unit to intercept the messages from phone answer/hang up buttons to control an aftermarket bluetooth phone kit. Thanks!

 

I suggest purchasing a CANBUS interface (some of the embedded system manufacturers provide whole computers on SIMMs with CANBUS interfaces). The system always runs in "promiscuous mode" so it would be pretty easy to capture the data as you press the buttons on the steering wheel controls. Every device on CANBUS receives every message and it is up to the device to decide whether to use the data or not.

-s-

 

I've decided to build a canbus interface for my Palm T3. Canbus to RS232 can be acheived with a handful of IC's and will cost me far less than a commercial unit. I'll then do exactly as you suggest - hook it up and start pressing buttons! Thanks.

 

Don't forget to enable the phone in the instrument cluster (using Star Diagnosis) or else the steering wheel button for the phone will not send any messages!

Let us know how it goes.

-s-

 

Do I really need to enable it? My current CLK say's Function not supported, when I press the phone buttons. In order for the instrument cluster to know it's not supported the steering wheel must be sending the message? I had assumed the E will be the same (mine arrives in January). Whatever the case I'll post the full story. Thanks

 

Yes, it must be enabled.

However, some come enabled, some do not. Just make sure yours is... otherwise you'll be looking for CANBUS messages that won't be there.

-s-

 

BTW does somebody know any analog of Dension ICE link for MB?

 

That's a good idea. Fortunately engine and interior CANBUS are separate, or else you'd be looking at a lot of data!

I wanted to decode a multifunction steering wheel once as well for a different reason, but never got around to it. Keep us updated!

 

Will do, I'll start a new thread once I get started.

 

I bought a bunch of IC's a while back to make my own RS232-CAN interface. Just have got around to actually doing it. But I wanted to use it to activate features that would normally require Star Diag. to do. I figure it's just sending out CAN messages to turn features on. Anyone think it works differently?

 

I don't know for sure, but I would think it works something like this... One of the modules on the CAN will contain in non-volatile memory all of the config settings - on the w211 this is the Central Gateway, but on other models it could be the instrument cluster or whatever. The CAN-D diagnostics bus will usually have a direct connection to that module and I would expect that the StarDiag unit would communicate over this. Whether MB use any sort or cryptographic protection to prevent certain opertations is unknown (to me at least), but in any case without a StarDiag unit working out the protocol will be difficult. If you do have access to one you could 'sniff' the CAN and see if you can capture the messages for interpretation. I'm currently designing the PCB for my CAN to RS232 interface, but as mine is designed to work with the fault tolerant CAN-B it uses different voltage levels and resistor terminations to CAN-D which I think is the same high-speed CAN as used in the engine. I'm just looking to capture the messages from the steering wheel controls and use them to control an aftermarket phone.