Well, I finally finished my steering wheel radio controls project and found out
that on the 2001s and up with the J1853 bus (rounded radios), the steering-
wheel mounted controls work on all the radios, not just the ridiculously
expensive 'I-don't-want-a-cassette,-dammit' one. There are two circuits that
run through the clockspring to the steering wheel that are both multiplexed.
There's a MUX in the CTM that watches these two circuits (one for cruise, one
for radio controls) and sends a command down the bus based on the voltage drop
across the circuit. So each button is nothing but a resistor - no big deal.
On 97-00 trucks, there's a 5-button wheel valence while the 2001s have a 6-
button. A 2001 still recognizes the resistances used by a 2000 but they're in
the wrong place. The volume up and seek down are on the left, volume down and
seek up on the right. It was a pain in the butt to cut out the 1/10 watt
resistors in there and solder in some that would make them work how I wanted,
but it finally worked out. Granted, I don't get to use the buttons to do
whatever I want, but this makes for a good second place. If anyone ever thinks
of a good way to build a 5-channel or 6-channel time-division MUX, let me know -
I'd like to try it. But for now, if you have a new truck and no steering
wheel controls, go buy the little valence that fits on the back side of your
steering wheel and install it, I'm hooked on mine. Some adventurous soul
should try the 97-00 setup and see if they work too...
heh.. heh.. catching breath
Crit
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