interface steering wheel controls with an arduino (stepped resistor)
Inspired by https://www.youtube.com/watch?v=Caf-yBI9rHA&t=220s
SWC Interface: Arduino Micro (with ATmega32U4 chip)
The steering wheel controls with 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.
Test the wiring with a multimeter, set it to measure resistance. hook up the meter so it completes a circuit with the SWC. In sketch defined values are for specific car and resistance values, you should enter yours after measuring or add/remove if you have more/less controls introduced.
Used NicoHood/HID (instead of standard Keyboard) Consumer for support of media keys for music player, browser, etc, which is compatible out-of-box with most devices I've tested it on (Android devices with OTG support, Macbook, Windows PC). So you will need to install HID plugin to use this sketch properly.
Example of wiring, where orange one is GND and green one is analog input from car.
