Self-Calibration and Coordinate Conversion for a Touchpad or Touch Screen Computer Input Device
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
A touchpad or touch screen is attached to a computer via a hardware interface card occupying a slot on the computer's I/O bus. This interface card interrogates the analog membrane, interrupting the CPU at regular intervals as long as the membrane is being pressed. In addition, there is commonly a touch-gone interrupt whenever the membrane has not been pressed since the last interrogation. For effective use as a graphics input device, the sampling rate of the membrane should be approximately 100 samples per second; thus, the hardware must interrogate the device approximately every 10 milliseconds, and software making use of this information must clearly process the data in this time interval or less.