Abstract: A process for encoding the movement of a computer pointing device to better control a cursor or other object on a display. The process makes use of two assumptions relating to illegal transitions (skipped states) that enables information relating to such illegal transitions to be included in the encoding process that samples states of a waveform produced by a detector in the pointing device. The first assumption refers to the directional ambiguity of a skipped state. When examined logically, it can be determined that this directional ambiguity need not be a concern, because a pointing device moving fast enough so that states are missed is realistically unable to reverse direction so fast that subsequent samples of the waveform would miss the reversal. Therefore, if a state is skipped, it is a reasonable assumption to assign the direction to the skipped state determined from the preceding samples.

Abstract: Changes in the detent position of a detented control wheel used for the Z-axis in a pointing device are determined in a manner that avoids problems previously experienced. A detented wheel is coupled to an optical encoder that produces a quadrature output signal. A quadrature state table containing entries defining quadrature state change conditions that invoke position change indications is used to determine when transitions between detent positions are reported and includes provision for reporting transitions between detent positions even if quadrature states are missed. Also employed is a physical-to-logical quadrature state conversion scheme that enables the transition point between adjacent detent positions to be correctly determined within a controlled range relative to the adjacent detent positions, regardless of the physical quadrature state while the wheel is in a detent position.