Interest check: Camry/Scion Steering Wheel Control -> USB
I'm new to posting here, but I guess i've been lurking here for awhile now. Anyway, I was developing my carpc when I ran into the steering wheel control problem. I have a gen6 camry, but I'm fairly sure the wiring is the same for gen3 and up. I was browsing solutions for steering wheel control integration, and they all seem rather expensive - and unreliable. The most popular seems to be the SWI-X, but that is designed for headunit integration and emits IR signals, which you must then trap and intercept using an IR reciever - this seems overly complicated to me for such a simple human interface device, and very expensive - SWI-X costs ~50-60$.
my proposal is to construct a hardware interface to connect the 20pin connector directly to USB. I've researched the controls, and it seems that the steering wheel controls consist of 3 wires (pins 7,8,9) which use alternating resistance values to indicate which buttons are being pressed. This could be easily interpreted by a microcontroller. The goal is to keep the cost low. I estimate the parts required to be:
Circuit Board (~$3)
Atmel Attiny or Atmega microcontroller (20-pin, 4k flash) (~$3)
Harness for 20-pin connector (~$3)
USB connector (~$0.50)
Which would be about $12. The firmware would be relatively simple, and I should be able to do that in a day, and the circuit need not be overly complex. The main issue is finding a compatible connector. Also, if the other wires are used by something else, a pass through connector might be needed (though, in my camry, I only have 3 wires connected to this connector). The device would not require any drivers, it would appear as a human interface device, and the buttons would by default mapped to volume, up/down arrow keys, and (not sure about mode button yet).
I thought this project might benefit other people, and it would be nice to have a fabricated silkscreened board than my typical self-etched board... If enough interest gathers up, perhaps I can buy parts in bulk and sell them pre-made (for a small fee) or in kits.