Abstract: Methods and systems for implementing an improved mouse optical sampling scheme are disclosed. At least one counter state machine is used to control at least one PTR state machine. At least one PTR state machine is used at a sample rate in order to determine the appropriate output for the mouse. The sample rate is adjusted to minimize the system sensitivity to poor duty cycle regulation. In addition, Tmin value(s) are adjusted in order to optimize the duty cycle for each PTR state machine. The mouse output is then provided to the computer. Consequently, by optimizing the duty cycle for each PTR state machine and minimizing its sensitivity to poor duty cycle regulation, a greater dynamic range of optical components can be employed in the mouse.

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.

Abstract: An adaptive digital filter is provided to obtain improved measurement accuracy in an electronic instrument which has a front-end circuit for coupling to an input signal to be measured. An analog to digital converter converts the input signal received through the front-end circuit into a stream of measurement values during the measurement phase. The stream of measurement values are then provided to the adaptive digital filter which mathematically operates on them to remove the frequency response effects of the front-end circuit in a process of convolution in the time domain using a set of digital filter values obtained during the calibration phase. Because the frequency response requirements of the front-end circuit have been eased with the addition of the adaptive digital filter, a simpler front-end circuit with fewer components and with no need for manual adjustment may be employed in electronic instruments.

Abstract: A "component test" function is provided in a low-power, portable test instrument like a digital multimeter. A test stimulus waveform is synthesized digitally, and a digital trigger signal from the synthesizing circuitry is used to trigger acquisition of measurement data. A single-channel front end acquires voltage scan data over one cycle of the test stimulus waveform following the trigger point. Current scan data is later acquired through the same acquisition circuitry beginning at the same trigger point relative to the start of a later cycle of the stimulus waveform, so that the voltage and current scan data, although acquired separately, are very closely synchronized relative to the stimulus waveform, as a result of which they maintain their phase relationship. Stored voltage and current scan data are aligned accordingly and concurrently displayed so as to form a Lissajous pattern on a small display.