It's a Grand Jeep Cherokee and the remote interface at the back of the radio is a pulsed signal (looking very like Sony's S-Link or baseband IR). However I'm taking a tap off the wiring harness at the steering wheel which it a voltage level (or resistor level if I cut the original factory connection).

Some basic maths show that the with a 5V drive, 22K pull-up resistor (as shown in the dev faq) and using the sony resistor values from the dev faq produce a voltage level rising in 0.4V increments between 0.4V and 4V.

Currently I have six voltage levels which unfortunatly do not match the sony levels exactly.

What I really need to determine is if the PIC in the tuner returns packets for all voltage levels or just for the 'valid' bands (there are ten bands between ~0.4 and ~4V, the mid point being at 0.4v intervals. Each band has about 0.1v gap between the next).

If the PIC only retuns 'valid' results then I need to shift the Jeep levels into valid bands. If the PIC retuns a straight voltage from the a/d convertor then I hope I can re-define the valid bands using hijacks rhs_stalk command.

Anyway I'm off to the car to add a 2K resistor to the circuit as this show make the existing circuit a closer match to the sony stalk and to play with Hijack.

Oh, and before someone suggests changing the resistors in the steering wheel - I did think about this, but I hate airbags and I do want to re-sell this car at some point which will require putting it back to factory fit. And after what this Empeg cost me, there is noway I am going to giving it away in the car!!!!!!!