Apologies for bumping up this oldie, but I ran across it earlier today and became interested in this and decided I'd mess around with one a bit and see how it worked. Figured the info would do better here than in a new thread also.
The board has a HA1805, which is made by Microchip and seems to have no Datasheet online. It appears to be a PIC that's programmed from the factory with whatever, as it's also used in the SSG-2100 3D glasses, but I seriously doubt for the same thing. No idea if it can be reflashed or not, though it does have the pads on the PCB for it, but they could just be there for the initial programming.
The other IC is a 74HC4051, which is an 8 channel multiplexer, but only 5 of the channels are used.
Since there is no DS on the HA1805, one can only guess at what it does exactly, but after tracing everything out most of it's not too hard to figure what it could be. (Note that R6, R7, R8 and R9 are not on this schematic as they are just 0ohm jumpers for power and signals). They are both powered by a 3.3v source from the Guitar.
Pin 5 is a PWM output (scoped it) that is 20kHz and 50% Duty Cycle and 3v p/p when idle (not touched) then varies from 14% to 99% Duty Cycle depending on which pad is touched, and that changes in 9 different 'steps' depending. Green being the lowest value and Orange the highest for the 1, 3, 5, 7, and 9 steps that correspond to each of the 5 touch pads, and then any middle ground (touching between Green and Red for example) being the 2, 4, 6, and 8 steps.
The HA1805 switches the 4051 between the 5 different pads and seems too sample each one, most likely on an ADC channel setup as a CVD, a method mentioned earlier and linked to in this thread by hyper999, then it just varies the Duty Cycle of the PWM output depending on that reading.
This PCB is designed to work in the 360, Wii and PS3 Guitars, and while this one I traced out came from a 360 Guitar, it was setup to work for the Wii or PS3. I never really used it personally, didn't like it from the start, so I'm not sure if this one even works exactly like it's supposed too for the 360. The 360 setup has R1 and R2 populated with a 1k Resistor, which sets up a voltage divider and would make it's output when idle right at 0.8v (instead of the 1.6v it is now) which is what the Matrix controllers sit at on their Analog lines when idle, then it would vary from 0v (Min) to 1.6v (Max) just like the Sticks in the 360 controller. I haven't installed the 1k Resistors to confirm this yet, but it's on the list of things to mess with before I'm done with it and put it all back together. It could be this is taken care of on the main board in the Guitar as well, so not needed on the Slide board, again, something else to look at, but will be interesting to test none the less.
Using it to control buttons would be more of a hassle than it would be worth IMHO. You'd be coding up your own PIC to deal with the output of this one, and with Capacitance Touch ICs already out there that could be straight wired into a controller, it's just more unnecessary steps to deal with.
I messed with a QT Touch Sensor awhile back on a 360 controller for the Trigger, didn't really inspire me to keep at it then for gaming.
http://i50.photobucket.com/albums/f320/RDCXBG/QT_RF001.jpg - Pic of the QT IC wired to the controller.
RDCXBG - QT_RF002.mp4 - Cruddy video of it working
There are a pile of other Capacitance Touch Sensor ICs out that are far easier to work with and cheap as well, plenty for a few bucks or less depending on what you're looking for, and provided that SMT parts are your bag. Though as also already pointed out by Modded Matt, they're not as fast as pushing an actual button, not without being made really sensitive, and then you'll have to deal with them going off when you don't want them too. They're far better for things like menu navigation or ease of turning something on or off, but as an input for any kind of faster paced gaming, they're not on my list of things I'd recommend.
