I had given some thought to this as well, I think the way to go would be a D-Pad, maybe salvaged from an old video game controller. Use up/down for volume, left/right for seek, and if there's a center button, use that for mode. It should be compact and ergonomic.

Remember, what the head unit is looking for is just shorting out two pins with a resistor. It's going to be much easier with a discrete on/off switch than using a potentiometer or an analog joystick or anything like that that has variable resistance. You'll need some intermediate circuitry to turn that into the type of signal that the HU is looking for. I'm not an electronics guy and I really don't know what you'd need to do to make that conversion, so I'd lean towards simple switches and resistors.

@foglesre @nalc


so basically you are just bridging the poles with the correct resistors (or just a wire in case of 0 ohms) if I'm reading this all correctly.

the part that confuses me is how i connect 21/23 for my volume/seek and do 1 without a backfeed or am i wrong for thinking of this in terms of normal power/ground?

also how do i connect pin 21/23 to 6 poles per switch? just solder it off into branches? so that 1 wire becomes 3 (in the case of a single switch)?