Hi all!
I deceided to upgrade my car stereo with an aftermarket one. Since my car uses CAN protocol I cannot directly connect my new stereo to the existing harness. I have some extra Arduino Nanos so my question is: can I use an Arduino nano (or any other) as the adapter for my aftermarket stereo? If I understand correctly how the CANBUS system works, I have to use Arduino to decode the turn on signal for the stereo and pass 12v to the aftermarket stereo (I was thinking about using step up converter)? My car is BMW 118d (E87) if this is somehow useful info.
what is your canbus interface?
What do you mean by canbus interface? I have quadlock connector with CAN-Low and CAN-High wires.
Most cars usually have an ignition switched live available somewhere, although these days not usually to the stereo which as you know does its own power management via CAN. For example to power the cigarette lighter socket, but not have things plugged into that (phone chargers, dash cams, etc) drain the battery when the car is parked up.
Connecting to that switched 12v would be the normal way to power an aftermarket stereo. Most headunits have 2 power supply wires, a battery backup permanent one (draws minimal power) and a switched one which provides main power when ignition is on And drives things like the amp.
So not sure a step up converter is going to help you here. A 12v relay is what you need if you are really dead set on doing it via CANBUS. Then you will have quite a bit of work trying to work out which CAN messages to listen for. Most of this stuff is not well documented anywhere, at least that was my experience with Audi - maybe BWM are different....
You can power most Arduinos direct from the car 12v supply. Although you’ll probably want to use a switched live for that as well, and not leave it permanently powered. Even a few mA can add up when it comes to leaving your car for weeks (think summer holiday).