Transmission of differential optical detector signal over a single line
AssigneeLogitech Europe S.A.
InventorsMarc Bidiville, Bernhard Joss
Life of this patent
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Abstract
A sensor for sensing movement of an encoder. At least two sensors are mounted adjacent the encoder. Each of the sensors provides an output corresponding to the amount of movement. A pair of comparators are connected to the sensors to provide two signal outputs. The comparator outputs are then provided to a digital encoding circuit which encodes the signals as a multi-bit serial value on a single output line. The bit value can be read by forcing control pulses onto the output line through an input buffer connected to the same line. The use of the single output line eliminates the extra output pin of the prior art, enabling a three pin package to be used.
Claims12
A sensor chip for sensing movement of an encoder, said sensor chip comprising:
- at least two sensors, each of said sensors providing an electrical sensor output signal having an amplitude corresponding to an amount of movement of said encoder;
- a plurality of comparators coupled to said sensors to provide two signal outputs, said comparators being responsive to a plurality of said sensor output signals for comparing at least first and second ones of said sensor output signals and generating at least one comparator output signal representative of the magnitudes of said sensor output signals;
- and
- a digital encoding circuit, coupled to said comparators, to encode said comparator signals as a multi-bit serial value on a single output line of said sensor chip.
An optical sensor chip for sensing light corresponding to movement of an encoder positioned between said optical sensor chip and a light emitter, said optical sensor chip comprising:
- at least two photosensors, each of said photosensors providing an electrical photosensor output signal having an amplitude corresponding to an amount of light impinging on the respective photosensor;
- a plurality of comparators coupled to said photosensors to provide two differential signal outputs, said comparators being responsive to a plurality of said photosensor output signals for comparing at least first and second ones of said photosensor output signals and generating at least one comparator output signal representative of the relative magnitudes of said photosensor output signals;
- a digital encoding circuit, coupled to said comparators, to encode said comparator signals as a multi-bit serial value on a single output line of said optical sensor chip, said digital encoding circuit including
- a rotary encoder having inputs coupled to said plurality of comparators and providing parallel outputs, and
- a parallel to serial converter interface circuit having inputs coupled to said parallel outputs of said rotary encoder;
- an input buffer, having an input coupled to said single output line and an output coupled to said digital encoding circuit to clock said multi-bit serial value out of said digital encoding circuit, such that said digital encoding circuit is operated under external control via said single output line also used to transmit said multi-bit serial value;
- and
- an output buffer coupled between said digital encoding circuit and said single output line, said output buffer having limited drive capability so that a signal from said output buffer can be overridden by a control signal provided to said input buffer.
A cursor control device for controlling the position of a cursor on a video display screen, comprising:
- a housing;
- a user movable input;
- a rotary encoder coupled to said user movable input;
- and a sensor chip comprising:
- at least two sensors mounted in said housing adjacent said rotary encoder, each of said sensors providing an electrical sensor output signal having an amplitude corresponding to an amount of movement of said rotary encoder;
- a plurality of comparators coupled to said sensors to provide two differential signal outputs, said comparators being responsive to a plurality of said sensor output signals for comparing at least first and second ones of said sensor output signals and generating at least one comparator output signal representative of the relative magnitudes of said sensor output signals;
- and
- a digital encoding circuit, coupled to said comparators, to encode said comparator signals as a multi-bit serial value on a single output line of said sensor chip.
Dependencies are inferred from the claim text.