This was a very interesting and challenging project. In 6 weeks we needed to develop a touchscreen that interacted with  a rotary encoder to take very accurate length measurements.

Touchscreen & Control Board

This was a tight deadline and the unit cost needed to be under $60.00, the encoder cost was $25.00 so that left $35.00 for the touchscreen / processor / memory / PCB! The touchscreen need advanced graphics capabilities and needed to be able to display images. This was a tall order in such a tight deadline as we did not have the time or budget to write our own graphics library. Luckily there is a new graphics co-processor from FTDI that interfaces with small micro-controllers with limited resources and off loads all the drawing and LCD communication routines to a dedicated in-expensive chip; FT800 and FT801 http://www.ftdichip.com/EVE.htm.

The interface is under NDA so I don’t have a lot of graphics but here is one running a touch calibration:

Touch Calibration