Work in progress.
TODO: Complete the document. TODO: Improve videos (with no music, please).
In this document we describe the algorithms we use to make the touchscreen behave well. By "well" we mean that we can:
- Get reliable clicks with the stylus and with the finger
- Avoid further filtering in user space
- Avoid calibration in user-space. We believe X (and other programs) should be able to gather reliable data from /dev/input/eventX.
Openmoko developers and contributors have tried different approaches that have helped improve the touchscreen performance. As a result now we have a touchscreen filtering framework that we are using in Linux 2.6. We describe the current working solution as of December 2008 as it is in the andy-tracking branch of the Openmoko GIT repository.
If you think we can improve something please send us feedback.
We include videos showing how things improve as we add filters. In the videos we use a program that plots the points reported by the driver.