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You need two ADC channels one to read the X and Z values and one to read the Y values... You also need to switch in a positive to each plate... The ADC has eight channels but no way of swapping the positive supply.... Go to MikroElectronica and look at this book... The last example has a simple switching circuit.. http://www.mikroe.com/chapters/view/17/chapter-4-examples/
I drew up a circuit using a 4053... with a single ADC connected to a 8052 micro..
When A,B & C on the 4053 are low... You will be reading the X axis... When all three are high you will read the Y axis.
Unfortunately, you won't be able to read the z axis, as I cannot swap a Ground for a positive... It could be done if you supply a positive to the X axis whilst the 4053 is switched away from the ground...
PMatrix area detection (PMAD) The PMAD works in combination with the PMSE. It reduces the CPU load by processing the information provided by the PMSE. It returns information on the touched areas. The PMAD can be served by the DMA controller