This controller demonstrates how most resistive touch screen systems can be modified to provide independent sensing of two positions on the surface. A single pressure measurement is also provided with a third sensing layer.
A pair of SlideWide sensors (http://infusionsystems.com) are stuck to each other at right angles.
Instead of measuring single touch position for each axis using the well-known potential divider method I modified the pads and wire them to ground the “wiper” contact and measure the two end point resistances to this ground node to estimate the position of the outer most touch point pair.
I also included a sheet of piezoresistive fabric to measure a single pressure estimate. The SlideWide sensors flex sufficiently for a useful touch pressure range.