Upgrading my Chumby 8 kernel part 7: touchscreen
downtowndougbrown.com
downtowndougbrown.com
Calibration was always a tricky thing on the resistive screens, as the author has seen. Normally this was all built into ts_calibrate, as part of the abandoned tslib library that AFAIK is still being used in a lot of places.
The math behind ts_calibrate is covered pretty well in this old paper from Texas Instruments. It's a nice piece of work, you can convert a raw X/Y input to a finished coordinate with a simple set of multiplications and 6 coefficients.