System and method for sensing touches in capacitive panels
First Claim
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1. A multi-touch sensing system for estimating a location of at least one touch point, the multi-touch sensing system comprising:
- a panel;
a grid of conductor disposed on the panel, the grid of conductor configured to provide capacitances between rows and columns of the grid;
a driver array connected to the grid, the driver array configured to transmit a set of overlapping and independent row drive signals to the grid;
a receiver array connected to the grid for receiving column signals from the grid via a plurality of inputs, the receiver array configured to;
sense a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs;
pre-charge the plurality of inputs to increase a voltage detection accuracy;
pre-charge the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input;
equalize a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets; and
produce digital estimates of the column signals;
a signal processing system in communication with the driver array and the receiver array, the signal processing system configured to estimate a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals; and
a controller for transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel.
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Abstract
A multi-touch sensing system and a method for estimating a location of at least one touch point are provided. The multi-touch sensing system includes a panel, a grid of conductor disposed on the panel, a driver array connected to the grid, a receiver array connected to the grid, a signal processing system, and a controller. The method involves transmitting drive signals to the grid, receiving signals from the grid, estimating a capacitance, and transforming the capacitance into touch coordinates.
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Citations
20 Claims
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1. A multi-touch sensing system for estimating a location of at least one touch point, the multi-touch sensing system comprising:
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a panel; a grid of conductor disposed on the panel, the grid of conductor configured to provide capacitances between rows and columns of the grid; a driver array connected to the grid, the driver array configured to transmit a set of overlapping and independent row drive signals to the grid; a receiver array connected to the grid for receiving column signals from the grid via a plurality of inputs, the receiver array configured to; sense a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs; pre-charge the plurality of inputs to increase a voltage detection accuracy; pre-charge the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input; equalize a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets; and produce digital estimates of the column signals; a signal processing system in communication with the driver array and the receiver array, the signal processing system configured to estimate a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals; and a controller for transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of estimating a location of at least one touch point on a multi-touch sensing system, the method comprising:
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transmitting a set of overlapping and independent row drive signals to a grid using a driver array, wherein the grid comprises conductor disposed on a panel, the grid configured to provide capacitances between rows and columns of the grid; receiving column signals from the grid via a plurality of inputs using a receiver array, wherein receiving column signals comprises; sensing a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs; pre-charging the plurality of inputs to increase a voltage detection accuracy; pre-charging the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input; equalizing a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets; and producing digital estimates of the column signals; estimating a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals using a signal processing system; and transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification