Mutual capacitance measurement in a multi-touch input device
First Claim
1. A method for determining multiple touch events in a multi-touch sensor system having a capacitance measurement unit comprising a relaxation oscillator circuit, a pulse drive unit, and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes, the method comprising:
- connecting a first electrode in a first set of electrodes to the relaxation oscillator circuit within the capacitance measurement unit;
driving, with the pulse drive unit, a voltage or current pulse onto a second electrode in a second set of electrodes each time the relaxation oscillator circuit transitions from a charging state to a discharging state;
measuring, with the capacitance measurement unit, the mutual capacitance at a node corresponding to the first and second electrodes by measuring a frequency of the relaxation oscillator circuit; and
comparing the measured mutual capacitance at the node with a previously measured mutual capacitance corresponding to the node by comparing the frequency to a previously measured frequency corresponding to the node and determining whether the frequency deviates from the previously measured frequency;
reporting that the node has been touched if there has been a deviation from the previously measured frequency.
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Accused Products
Abstract
Systems and methods for determining multiple touch events in a multi-touch sensor system are provided. The system may include a capacitance measurement unit, a pulse drive unit, and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes. The method may include connecting a first electrode in a first set to the capacitance measurement unit, the pulse drive unit driving a voltage or current pulse onto a second electrode in a second set of electrodes. The method may further include the capacitance measurement unit measuring the mutual capacitance at a node corresponding to the first and second electrodes. The method may include comparing the measured mutual capacitance at the node with a previously measured mutual capacitance for the node, and reporting that the node has been touched if there has been a deviation from the previously measured mutual capacitance.
30 Citations
24 Claims
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1. A method for determining multiple touch events in a multi-touch sensor system having a capacitance measurement unit comprising a relaxation oscillator circuit, a pulse drive unit, and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes, the method comprising:
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connecting a first electrode in a first set of electrodes to the relaxation oscillator circuit within the capacitance measurement unit; driving, with the pulse drive unit, a voltage or current pulse onto a second electrode in a second set of electrodes each time the relaxation oscillator circuit transitions from a charging state to a discharging state; measuring, with the capacitance measurement unit, the mutual capacitance at a node corresponding to the first and second electrodes by measuring a frequency of the relaxation oscillator circuit; and comparing the measured mutual capacitance at the node with a previously measured mutual capacitance corresponding to the node by comparing the frequency to a previously measured frequency corresponding to the node and determining whether the frequency deviates from the previously measured frequency; reporting that the node has been touched if there has been a deviation from the previously measured frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for determining multiple touch events in a multi-touch sensor system having a capacitance measurement unit, a pulse drive unit, a timer and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes, wherein the capacitance measurement unit comprises a voltage or current source, the method comprising:
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connecting a first electrode in a first set of electrodes to the voltage or current source of the capacitance measurement unit; driving, with the pulse drive unit, a voltage or current pulse onto a second electrode in a second set of electrodes while the voltage or current source is connected to the first electrode; starting the timer and measuring the voltage of the first electrode as a measured voltage when the timer reaches a pre-determined time; comparing the measured voltage to a previously measured voltage corresponding to the node; and reporting that the node has been touched if the measured voltage deviates from the previously measured voltage. - View Dependent Claims (11, 12, 13, 14)
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15. A method for determining multiple touch events in a multi-touch sensor system having a capacitance measurement unit, a pulse drive unit, a timer and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes, wherein the capacitance measurement unit comprises a voltage or current source, the method comprising:
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connecting a first electrode in a first set of electrodes to the voltage or current source; driving, with the pulse drive unit, a voltage or current pulse onto a second electrode in a second set of electrodes while the voltage or current source is connected to the first electrode; starting the timer, measuring the voltage of the first electrode as a measured voltage, and storing the time value of the timer when the measured voltage reaches a pre-determined voltage level; comparing the stored time value to a previously stored value corresponding to the node; and reporting that a node corresponding to the first and second electrodes has been touched if the stored time value deviates from the previously stored value. - View Dependent Claims (16, 17, 18, 19)
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20. A system for detecting one or more touch events on a touch sensor, comprising:
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a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least a first and second set of electrodes; a touch controller having a pulse drive circuit selectably coupled to the plurality of electrodes, a timer circuit, a capacitance measurement unit comprising a charge time measurement circuit selectably coupled to the plurality of electrodes and coupled with the timer circuit; and
a storage element coupled to the charge time measurement, circuit;wherein the touch controller is operable to; measure the mutual capacitance at a node corresponding to a first electrode in the first set of electrodes and a second electrode in the second set of electrodes by; coupling a voltage or current source in the charge time measurement circuit to the first electrode; starting the timer circuit; coupling the second electrode to the pulse drive circuit; and measuring the voltage of the first electrode as a measured voltage when the timer circuit reaches a predetermined time; compare the mutual capacitance at the node with a previously measured mutual capacitance corresponding to the node by comparing the measured voltage to a previously measured voltage corresponding to the node; and report that the node has been touched if there has been a deviation from the previously measured voltage. - View Dependent Claims (21, 22)
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23. A system for detecting one or more touch events on a touch sensor, comprising:
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a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least a first and second set of electrodes; a touch controller having a pulse drive circuit selectably coupled to the plurality of electrodes, a timer circuit, a capacitance measurement unit comprising a charge time measurement circuit selectably coupled to the plurality of electrodes and coupled with the timer circuit; and
a storage element coupled to the charge time measurement circuit;wherein the touch controller is operable to measure the mutual capacitance at a node by; coupling a voltage or current source in the charge time measurement circuit to the first electrode; starting the timer circuit; coupling the second electrode to the pulse drive circuit; measuring the voltage of the first electrode as a measured voltage; and storing, in the storage element, the time value of the timer circuit when the measured voltage reaches a predetermined voltage level; wherein the touch controller compares the mutual capacitance at the node by comparing the stored time value to a previously stored time value corresponding to the node; and wherein the touch controller reports that the node corresponding has been touched if the stored time value deviates from the previously stored time value.
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24. A system for detecting one or more touch events on a touch sensor, comprising:
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a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least a first and second set of electrodes; a touch controller having a pulse drive circuit, and a relaxation oscillator-based measurement circuit; wherein the touch controller is operable to measure the mutual capacitance at a node by; coupling the relaxation oscillator-based measurement circuit to a first electrode in the first set of electrodes; coupling a second electrode in the second set of electrodes to the pulse drive circuit; and measuring the frequency of the relaxation oscillator-based measurement circuit; wherein the touch controller compares the mutual capacitance at the node by comparing the frequency to a previously measured frequency corresponding to the node and determines whether the frequency deviates from the previously measured frequency; and wherein the touch controller reports that the node has been touched if there has been a deviation from the previously measured frequency.
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Specification