You should check this links, to create the electronics: https://www.instructables.com/Digital-Potentiometer-MCP41100-and-Arduino/ and https://forum.arduino.cc/t/steering-wheel-remote-audio-control/223878/6
This code used to control the digital potentiometer MCP41100-E/P connected to arduino Board.
CS -- D10
SCLK -- D13
DI -- D11
PBO, Audio jack GND -- GND
PW0 -- Pioneer radio over jack tip.
5v -- Car's steering wheel input cable.
A4 -- Car's steering wheel output cable.