Jeffrey D Sharp

US Patent:

6630929, Oct 7, 2003

Filed:

Sep 29, 1999

Appl. No.:

09/408594

Inventors:

Robert Adler - Northbrook IL
Joel Kent - Fremont CA
Jeffrey L. Sharp - Ruckersville VA
Geoffrey D. Wilson - Oxnard CA

Assignee:

ELO Touchsystems, Inc. - Fremont CA

International Classification:

G09G 500

US Classification:

345177, 345173, 345176, 178 1804

Abstract:

A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilize look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator. The reference oscillator output is used to control the frequency of the signal from the receiving transducers and/or to generate the desired frequency of the tone burst sent to the transmitting transducers. In another embodiment that is intended to compensate for both global and local frequency variations, the adaptive controller uses a digital signal processor.