Pointing stick device
First Claim
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1. A pointing stick device, comprising:
- a signal source element which comprises a plurality of strain gauges for sensing forces exerted onto a pointing stick and generating voltage signals;
a voltage approaching element providing an incremental voltage for comparing with said voltage signals generated by said signal source element, wherein said voltage approaching element comprises a voltage division circuit providing a predetermined voltage to said incremental voltage according to said strain gauges of said signal source element, a first approaching unit lifting said incremental voltage close to said voltage signals such that said incremental voltage is lifted not to exceed said voltage signals, and a second approaching unit lifting said incremental voltage linearly, wherein said first approaching unit comprises a first current source, a first approaching capacitor, and a first switch for coarse approaching and for adjusting an error introduced by an inaccuracy of resistors, wherein said first approaching capacitor is connected with said first current source through said first switch, wherein when said first switch is closed in a predetermined period of time, said first approaching capacitor is charged to a predetermined voltage level, wherein said second approaching unit comprises a second current source, a second approaching capacitor, and a second switch, wherein said second approaching capacitor is connected with said second current source through said second switch, wherein when said second switch is closed, said second approaching capacitor is being charged while said incremental voltage is lifted linearly with a predetermined rate, wherein said first and second current sources are programmable to provide different values; and
a signal process element comparing said voltage signals of said signal source element and said incremental voltage of said voltage approaching element, and counting the time for said incremental voltage to reach to a level related to said voltage signals for calculating said forces exerted onto said pointing stick.
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Abstract
The present invention provides a pointing stick device circuit which is using fewer components. The circuit is using current sources instead of voltage sources. This will be more convenient to integrate the circuit and largely reduce the cost. Also, using this circuit and the relative process, the requirement of high quality and low tolerance of some critical components is reduced. The performance of the device is improved.
16 Citations
15 Claims
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1. A pointing stick device, comprising:
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a signal source element which comprises a plurality of strain gauges for sensing forces exerted onto a pointing stick and generating voltage signals; a voltage approaching element providing an incremental voltage for comparing with said voltage signals generated by said signal source element, wherein said voltage approaching element comprises a voltage division circuit providing a predetermined voltage to said incremental voltage according to said strain gauges of said signal source element, a first approaching unit lifting said incremental voltage close to said voltage signals such that said incremental voltage is lifted not to exceed said voltage signals, and a second approaching unit lifting said incremental voltage linearly, wherein said first approaching unit comprises a first current source, a first approaching capacitor, and a first switch for coarse approaching and for adjusting an error introduced by an inaccuracy of resistors, wherein said first approaching capacitor is connected with said first current source through said first switch, wherein when said first switch is closed in a predetermined period of time, said first approaching capacitor is charged to a predetermined voltage level, wherein said second approaching unit comprises a second current source, a second approaching capacitor, and a second switch, wherein said second approaching capacitor is connected with said second current source through said second switch, wherein when said second switch is closed, said second approaching capacitor is being charged while said incremental voltage is lifted linearly with a predetermined rate, wherein said first and second current sources are programmable to provide different values; and a signal process element comparing said voltage signals of said signal source element and said incremental voltage of said voltage approaching element, and counting the time for said incremental voltage to reach to a level related to said voltage signals for calculating said forces exerted onto said pointing stick. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of sensing forces exerted on a pointing stick device, comprising the steps of:
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(a) resetting a circuit of said pointing stick device; (b) sampling a signal source from said circuit; (c) increasing an incremental voltage via a first approaching unit to a predetermined voltage level, wherein said first approaching unit comprises a first current source, a first approaching capacitor, and a first switch for coarse approaching and for adjusting an error introduced by an inaccuracy of resistors, wherein said first approaching capacitor is connected with said first current source through said first switch, wherein when said first switch is closed in a predetermined period of time, said first approaching capacitor is charged to a predetermined voltage level; (d) linearly increasing said incremental voltage via a second approaching unit at a predetermined linear incremental rate, wherein said second approaching unit comprises a second current source, a second approaching capacitor, and a second switch, wherein said second approaching capacitor is connected with said second current source through said second switch, wherein when said second switch is closed, said second approaching capacitor is being charged while said incremental voltage is lifted linearly with a predetermined rate, wherein said first and second current sources are programmable to provide different values; (e) comparing said voltage signal of said sampled signal source with said incremental voltage from said second approaching unit; and (f) determining a time for said incremental voltage in responsive to said incremental rate thereof for calculating said force exerted onto said pointing stick device. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification