CAN Bus

microkid · 06-09-2008, 11:21 AM

Ok I am trying to back engineer the cd changer protocol of my Alfa factory fit blaupunkt head unit.

To make this easier I thought I would set it up in my workshop hook up to a scope, and PC and have it cracked in minutes.

But I cant even switch on - i get the error message 'can bus error' so i am guessing I need the unit plugged into the can bus.

does anyone know anyway around this? Can I power it up in 'non can' mode by holding down some buttons? Is there an easier way to make it think the can is there?

Any suggestions :-)

dementeddigital · 06-15-2008, 05:16 PM

Since CAN busses need termination, you could try putting a 60 ohm resistor across CAN_H and CAN_L. The bus will indicate an error with no resistor.

If your CD changer needs to communicate with the head unit, you'll probably need them connected together. (It still may not power-up without being connected.) You'll probably want them connected to reverse-engineer the protocol anyway.

What CAN interface are you using for this?