The steering wheel controls were actually quite simple. I checked out the wiring diagram for the subaru svx and found that there are two wires controling the three buttons. One wire went high (positive) when one button was pressed, the other high when the other button was pressed, and then they both went high when the middle button was pressed. To make life easy I used a digital decoder and hooked up the two wires to it. I tied the enable line of the decoder to the cruise control ON button so that everytime I wanted to use the cruise control, my circuit would shut down and the car's cruise control would work just like normal.
The 2to4 decoder would read the inputs and make the correct output high accordingly. Decoder's are awesome because they can become pretty complex without the use of relays.
I bought a very cheap keyboard for $5, took it apart and traced to the keys I needed. The circuit acts by when the cruise control button is pressed, a hot key is pressed on the keyboard which activates the function on the computer ...pretty simple.
Once I have the correct output for each cruise control button I fed the circuit into transistors so that I can switch relays from the low current decoder. I decided to use three combinations:
CTRL+ALT+D - Volume Down
CTRL+ALT+U - Volume Up
ScrollLock - Activate Voice Recognition
ScrollLock required just one relay, but the ctrl+alt commands were different. I had to delay the relays hitting ctrl+alt so that those buttons were pressed before the D or U......if not the computer wouldn't know CTRL+ALT+key was pressed. I just threw a capacitor in parallel with the key buttons to delay them and it worked.
I hope that helped. I do have a schematic floating around somewhere, but it is quite basic:
Subaru Cruise Module -> Digital Decoder -> Boost Transistors -> Relays -> Keyboard Card from Keyboard.
Here's a picture:
http://www.expertwebcreations.com/pe...escription.jpg
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The PXA-H701 only takes RCA or optical inputs. So I bought an Coax -> Optical converter which works flawlessly. I have one problem which is very annoying though - I cannot control the SP/DIF volume from the santa cruz, but I can control the WAV volume. So basically, I have to adjust the volume from the DSP which makes my steering wheel controls somewhat useless. I don't know if it's just the santa cruz sound card or it's something with the coax -> optical conversion.
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