I have updated the touch controller!! It seemed a little unstable.. Usable, but unstable..
Using two ADC inputs and two 100k resistors is all that's needed.. ( You can use two 47nF decoupling caps, but I don't read the ADC's too fast and I need a bit of noise as I oversample... Up to you ).
You only ever need to read two of the wire's... X+ and Y-.
First look at the schematic..
To read your X plane Tris state Y+ and Y- ... Place logic 1 on X+ and logic 0 on X-.. Read Y-.
To read your Y plane Tris state X+ and X- ... Place logic 1 on Y+ and logic 0 on Y-.. Read X+.
Now there is another plane you need to worry about.... The Z plane!! This is how much pressure has been applied to the panel..
To read the Z plane you need to do the same as you do for the X plane but both X+ and X- are given a logic 1 and when you read the Y- pin the higher the value the harder the press... BUT!!! The reading is logarithmic, so the threshold has to be set high.. on a 10 bit ADC you are looking at an ADC reading of 950 +..
The Z plane sensitivity can be increased by using lower pulldown resistors... I have seen them as low as 300ohm but as the screen planes are in the order of 300 ohm it will decrease the sensitivity of the X and Y planes...
The beauty of the Z plane is, you only need to read the X and Y values when a valid press is detected...