how to: interface steering wheel controls with an arduino (stepped resistor)

I show you how i interfaced my SWC(steering wheel controls) to crankshaft. A linux distribution for running android auto.

Components:
Car: 2005 Jaguar X-Type
Computer: Raspberry pi model 3B+
SWC Interface: Arduino Micro (with ATmega32U4 chip for usb support)
custom protoboards: voltage divider circuit, optocoupler circuit

Arduino micro listing:
https://www.amazon.com/Arduino-Micro-Headers-A000053-Controller/dp/B00AFY2S56
Documentation:
The steering wheel controls in this case is a stepped resistor. This required analog interpretation of multiple buttons over a single wire. If you have separate wires per button (probably not due to clock spring restrictions in a lot of steering wheels), then it is way easier. just hook up the gpio connectors through an optocoupler board.

Find out what the wiring in you car looks like. Just google for the wiring schematics and search for the infotainment part. For my car it showed up in google at the top (section 15.1 is relevant here): http://www.jagrepair.com/images/Electrical/XTypeElectrical/2005%20MY%20X-TYPE%20Electrical%20Guide.pdf

Test the wiring with a multimeter, set it to measure resistance. hook up the meter so it completes a circuit with the SWC.

Hook up the arduino with script + voltage divider.
script:
https://pastebin.com/3XwwJAgi
voltage divider:
https://www.khanacademy.org/science/electrical-engineering/ee-circuit-analysis-topic/ee-resistor-circuits/a/ee-voltage-divider

Connect the arduino to the RPI running crankshaft / another system and setup the software to read GPIO or accept keyboard commands

...

I know I could've bought a control unit that does all this for me, but where is the fun and learning in that :) Ofcourse im not responsible for your ability to think clearly and that you should not use this while driving, or basically doing anything fun ever. dont get distracted, dont run over people, blablabla disclaimer, dont judge me for stupid actions or breaking your car or parts of you car blablabla.

Видео how to: interface steering wheel controls with an arduino (stepped resistor) канала Rutger de Graaf