The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 23, 2001
Filed:
Nov. 13, 1998
Daniel D. Claxton, Rancho Santa Fe, CA (US);
Qualcomm Incorporated, San Diego, CA (US);
Abstract
A method and apparatus for calibrating a resistive ladder switching matrix coupled to a keypad in a portable electronic device having a housing with a cover that may be positioned in an open state or a closed state. A first contact of a calibration element is coupled to a reference voltage and a second contact of the calibration element is coupled to ground by moving the cover from the open state to the closed state. When the first contact of the calibration element is coupled to the reference voltage and the second contact of the calibration element is coupled to ground, a calibration resistance across the calibration element is determined. The calibration resistance may correspond to an input impedance of the resistive ladder switching matrix when no buttons associated with the keypad are depressed. Signals from the resistive ladder switching network are calibrated when the cover is in the closed state in accordance with the calibration resistance.