Browse Prior Art Database

Device Driver for a Touchpad or Touch Screen Computer Input Device

IP.com Disclosure Number: IPCOM000040059D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

Reed, MA: AUTHOR

Abstract

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 with status information and positional data, as long as the membrane is being pressed. There are two sections to the resident device driver software for a touchpad or touch screen input device. The device interrupt handler receives control for every touch on the device. It reads the status and data bytes, filters the raw X,Y data, and converts it to normalized (Image Omitted) format.

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Device Driver for a Touchpad or Touch Screen Computer Input Device

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 with status information and positional data, as long as the membrane is being pressed. There are two sections to the resident device driver software for a touchpad or touch screen input device. The device interrupt handler receives control for every touch on the device. It reads the status and data bytes, filters the raw X,Y data, and converts it to normalized

(Image Omitted)

format. The raw X,Y values presented to this device driver program are the result of an analog-to-digital conversion of the analog samples in each cartesian coordinate direction by the interrogation circuitry on the hardware adapter card. The raw X,Y values will have a range dependent on the resolution of the A/D process (e.g., a 10-bit A/D result will theoretically yield digital values in the range 0-1023, a 12-bit A/D in the range 0-4095). However, due to hardware self-calibration circuitry, reference voltage drift, clipping, housing design (possibly preventing access to the extreme boundaries of the input device), and other hardware considerations, the actual digital range presented to the software interrupt handler will be somewhat less. The device interrupt handler also performs self-calibration of the device with use, sets/resets internal flags, optionally moves a screen cursor, a...