Patent ID: 6380927
Filing Date: 2002-04-30
Classification: G06F

Abstract:
A method for detecting a change in a detent position of a detented wheel operatively coupled to an optical encoder that produces a quadrature output signal comprising a first, a second, a third, and a fourth quadrature state as the detented wheel is rotated in a forward or a reverse direction between successive detented positions, the method comprising the steps of:(a) monitoring and processing the quadrature output signal from the optical encoder as the detented wheel is rotated, the quadrature output signal that is processed comprising a plurality of successive quadrature states; (b) defining quadrature state change conditions that invoke position change indications corresponding to a change in the detent position, such that in each of the forward and reverse directions, there exists a single predefined quadrature state change condition between a predefined pair of adjacent quadrature states that invokes a position change indication corresponding to the direction, the quadrature state change conditions compensating for a missing quadrature-state change in detecting a change in detent position; and (c) outputting position change indications based on changes between successive quadrature states and the quadrature state change conditions that are defined, so as to provide an indication of the rotation direction and an amount of rotation of the detented wheel.