Alfa Romeo 156 2.0 JTS has resistive steering wheel remote controls.
It can be connected directly to CarPC JoyCon EX.

The resistance value is:

RC-A:
Mute : 390
Vol Up : 170
Vol Down : 70

RC-B:
SRC : 391
Forward : 171
Backward :71

Left and right resistance value is duplicated, so a resistor is needed to avoid duplication.

If you use CarPC JoyCon EX, you don’t need a resistor to avoid duplication.
RC-A -> DATA of CarPC JoyCon EX channel A
RC-B -> DATA of CarPC JoyCon EX channel B
GND -> GND of CarPC JoyCon EX