Apparatus and method for digitizer sampled point validation
First Claim
1. An apparatus for determining the validity of a point sampled from a digitizer having upper and lower resistive layers, each layer containing a plurality of electrodes, the apparatus comprising:
- drive means for driving the digitizer with one of a plurality of drive sources;
selection means coupled to the drive means for determining which drive source is coupled to the digitizer;
means for sensing a predetermined electrical parameter at a predetermined number of electrodes coupled to the digitizer; and
control means coupled between the sensing means and the selection means for controlling the selection means, and for determining the contact resistance between the upper and lower resistive layers at at least one point of contact between the two layers and comparing the contact resistance to a valid range of contact resistances to either accept or reject the point;
wherein a contact resistance below the valid range is indicative of a plurality of points of contact and a resistance above the valid range is indicative of insufficient pressure at the point of contact.
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Abstract
An apparatus and method for digitizer sampled point validation which determines the contact resistance at a point of contact between the upper and lower layers of the digitizer and compares the contact resistance with a valid range of contact resistances to either accept or reject the sampled point. The apparatus includes an analog drive circuit for driving the digitizer with one of a plurality of drive sources, a switch control logic coupled to the drive circuit for determining which drive source is coupled to the digitizer, an analog-to-digital convertor coupled to the digitizer, and a microcontroller coupled between the analog-to-digital convertor and the switch control logic. The method of the present invention determines the contact resistance, compares the contact resistance with the valid range, and determines and stores the location of the point if the contact resistance is within the valid range.
23 Citations
50 Claims
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1. An apparatus for determining the validity of a point sampled from a digitizer having upper and lower resistive layers, each layer containing a plurality of electrodes, the apparatus comprising:
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drive means for driving the digitizer with one of a plurality of drive sources; selection means coupled to the drive means for determining which drive source is coupled to the digitizer; means for sensing a predetermined electrical parameter at a predetermined number of electrodes coupled to the digitizer; and control means coupled between the sensing means and the selection means for controlling the selection means, and for determining the contact resistance between the upper and lower resistive layers at at least one point of contact between the two layers and comparing the contact resistance to a valid range of contact resistances to either accept or reject the point; wherein a contact resistance below the valid range is indicative of a plurality of points of contact and a resistance above the valid range is indicative of insufficient pressure at the point of contact. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for determining the validity of a point sampled from a digitizer having upper and lower resistive layers comprising:
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drive means for driving the digitizer with one of a plurality of drive sources including a current source, a voltage source, a ground, and switching means for coupling the sources and the ground to the digitizer; selection means coupled to the drive means for determining which drive source is coupled to the digitizer including a latch; an analog-to-digital converter coupled to the digitizer; and control means coupled between the analog-to-digital converter and the selection means for controlling the selection means, for determining the contact resistance at at least one point of contact between the upper and lower resistive layers, for determining the coordinates of the point of contact between the upper and lower resistive layers, and for comparing the contact resistance to a valid range of contact resistance to either accept or reject the point; wherein a contact resistance below the valid range is indicative of a plurality of points of contact and a resistance above the valid range is indicative of insufficient pressure at the point of contact.
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11. A method for determining the validity of a point sampled from a digitizer having upper and lower resistive layers, each containing a plurality of electrodes, the method comprising the steps of:
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(a) determining the contact resistance at at least one point of contact between the upper and lower layers; (b) comparing the contact resistance to a range of valid contact resistances; (c) if the contact resistance is within the valid range, determining the location of the point and accepting the location; and (d) if the contact resistance is above the valid range, which is indicative of a plurality of points of contact, or if the contact resistance is below the valid range, which is indicative of insufficient pressure at the point of contact, rejecting the location. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method for determining the contact resistance at a point of contact between the upper and lower layers of a digitizer comprising the steps of:
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(a) measuring a first voltage across the upper layer; (b) measuring a second voltage across the lower layer; (c) measuring a third voltage across a first portion of the upper layer and a first portion of the lower layer, the first portions being joined by the point of contact; (d) measuring a fourth voltage across a second portion of the upper layer and a second portion of the lower layer, the second portions being joined by the point of contact; and (e) determining the difference between the sum of the first and second voltages and the sum of the third and fourth voltages.
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27. An apparatus for determining the validity of a point sampled from a digitizer having upper and lower resistive layers, each layer containing a plurality of electrodes, the apparatus comprising:
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drive means for driving the digitizer with one of a plurality of drive sources, including a current source coupled to one electrode, and a ground for the current source coupled to another electrode, wherein the one electrode is in the same layer as the other electrode; selection means coupled to the drive means for determining which drive source is coupled to the digitizer; means for sensing a predetermined electrical parameter at a predetermined number of electrodes coupled to the digitizer; and control means coupled between the sensing means and the selection means for controlling the selection means, and for determining the contact resistance between the upper and lower resistive layers at a point of contact between the two layers and comparing the contact resistance to a valid range of contact resistances to either accept or reject the point. - View Dependent Claims (28, 29, 30, 31, 32)
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33. A method for determining the validity of a point sampled from a digitizer having upper and lower resistive layers, each containing a plurality of electrodes, the method comprising the steps of:
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(a) determining the contact resistance at a point of contact between the upper and lower layers, including the substeps of; (a-1) measuring a first voltage across the upper layer, measuring a second voltage across the lower layer; (a-2) measuring a third voltage across a first portion of the upper layer and a first portion of the lower layer wherein the first portions are joined by the point of contact; (a-3) measuring a fourth voltage across a second portion of the upper layer and a second portion of the lower layer wherein the second portions are joined by the point of contact; (a-4) and determining the difference between the sum of the first and second voltages and the sum of the third and fourth voltages; (b) comparing the contact resistance to a range of valid contact resistances; (c) if the contact resistance is within the valid range, determining the location of the point; and (d) accepting the location. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification