Constant calibration
First Claim
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1. A method for tuning an oscillator of an event-sensitive device, comprising:
- programmably configuring calibration logic to perform a first calibration process to initially tune the oscillator to a desired frequency, the first calibration process includingapproximating a number of cycles of the desired frequency in one cycle of a reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, anditeratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles; and
programmably reconfiguring the calibration logic to perform a second calibration process to maintain the oscillator at the desired frequency, the second calibration process includinginitiating the second calibration process on a periodic basis by activating the reference signal, the initiation being independent of any detected frequency drift,setting a threshold value corresponding to an acceptable frequency variation range,determining an error count corresponding to a difference between the measured oscillator frequency and an approximated frequency associated with the approximated number of cycles,determining if the error count exceeds the threshold value,tuning the oscillator to a frequency that is closer to the approximated frequency if the error count exceeds the threshold value, anddiscontinuing the second calibration process by deactivating the reference signal to conserve power during normal operation.
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Abstract
An oscillating signal of relatively precise frequency can be generated by tuning an oscillator using an external stable oscillating source as a reference. Calibration logic can be included to compare a signal from the local oscillator to the reference signal and vary the local signal to a desired frequency. In one embodiment, the frequency of the local signal can be constantly or periodically compared with a threshold value and if the frequency exceeds the threshold value, the local oscillator can be modified to produce a signal having a frequency that is closer to a desired frequency.
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Citations
29 Claims
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1. A method for tuning an oscillator of an event-sensitive device, comprising:
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programmably configuring calibration logic to perform a first calibration process to initially tune the oscillator to a desired frequency, the first calibration process including approximating a number of cycles of the desired frequency in one cycle of a reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles; and programmably reconfiguring the calibration logic to perform a second calibration process to maintain the oscillator at the desired frequency, the second calibration process including initiating the second calibration process on a periodic basis by activating the reference signal, the initiation being independent of any detected frequency drift, setting a threshold value corresponding to an acceptable frequency variation range, determining an error count corresponding to a difference between the measured oscillator frequency and an approximated frequency associated with the approximated number of cycles, determining if the error count exceeds the threshold value, tuning the oscillator to a frequency that is closer to the approximated frequency if the error count exceeds the threshold value, and discontinuing the second calibration process by deactivating the reference signal to conserve power during normal operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 24)
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8. A method for tuning a frequency of an oscillating signal comprising:
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programmably configuring calibration logic to perform a first calibration process to initially tune the oscillating signal to a desired frequency, the first calibration process including approximating a number of cycles of the desired frequency in one cycle of a reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles; and programmably reconfiguring the calibration logic to perform a second calibration process to maintain the oscillating signal at the desired frequency, the second calibration process including initiating the second calibration process on a periodic basis by activating the reference signal, the initiation independent of any detected frequency drift, determining a desired clock count corresponding to an approximated frequency of associated with the approximated number of cycles, outputting a local the measured oscillator frequency, counting a measured clock count corresponding to the measured oscillator frequency, determining an error count based on the measured clock count, comparing the error count with a threshold value, modifying the oscillator frequency of the local oscillator signal to a second frequency if the error count exceeds the threshold value, and discontinuing the second calibration process by deactivating the reference signal to conserve power during normal operation. - View Dependent Claims (9, 10, 11)
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12. A multi-event sensor device comprising:
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a local oscillator circuit configured to generate an oscillating signal having a frequency at least partially based on an incoming control signal; a reference signal generator configured to be activated and generate a reference signal to initiate first and second calibration processes, the second calibration process initiated on a periodic basis independent of any detected frequency drift, and further configured to be deactivated to discontinue the first and second calibration processes and conserve power; and programmable calibration logic configurable to perform the first calibration process to initially tune the local oscillator circuit to a desired frequency, and reconfigurable to perform the second calibration process to maintain the local oscillator circuit at the desired frequency by comparing the frequency of the oscillating signal with a frequency of the reference signal and re-tuning the local oscillator circuit so that the frequency of the local oscillator circuit falls within a desired range; wherein the programmable calibration logic is configured to perform the first calibration process by approximating a number of cycles of the desired frequency in one cycle of the reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A multi-event sensor device, comprising:
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oscillator generation means for generating an oscillating signal; reference signal generation means configured to be activated and generate a reference signal to initiate first and second calibration processes, the second calibration process initiated on a periodic basis independent of any detected frequency drift, and further configured to be deactivated to discontinue the first and second calibration processes and conserve power; programmable calibration means configurable for performing the first calibration process to initially tune the oscillator generation means to a desired frequency, and reconfigurable for performing the second calibration process to maintain the oscillator generation means within a predetermined range; and event sensitive means for sensing a plurality of events occurring simultaneously or nearly simultaneously on an event-sensing panel; wherein the programmable calibration means are configured to perform the first calibration process by approximating a number of cycles of the desired frequency in one cycle of a reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles. - View Dependent Claims (20)
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21. An electronic device comprising:
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an event sensitive panel configured to receive an oscillating signal and generate an output signal based on the received oscillating signal; an oscillating circuit configured to generate the oscillating signal having a frequency; a reference signal generator configured to be activated and generate a reference signal to initiate first and second calibration processes, the second calibration process initiated on a periodic basis independent of any detected frequency drift, and further configured to be deactivated to discontinue the first and second calibration processes and conserve power; and a programmable calibration controller configurable to perform the first calibration process by initially tuning the oscillating circuit to a desired frequency, and reconfigurable to perform the second calibration process to maintain the oscillating signal within the desired frequency range; wherein the programmable calibration controller is configured to perform the first calibration process by approximating a number of cycles of the desired frequency in one cycle of the reference signal by multiplying a programmable value and a granularity factor, the granularity factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles. - View Dependent Claims (22, 23)
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25. An apparatus for stimulating a touch sensor panel, comprising:
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a reference oscillator configured for generating a reference signal only during a calibration phase; a local oscillator circuit including a voltage controlled oscillator configured for receiving a control signal and generating a clock signal for use in stimulating the touch sensor panel; and programmable calibration logic coupled between the reference oscillator and the local oscillator circuit for receiving the reference signal and the clock signal and generating the control signal; wherein the programmable calibration logic is configurable for entering a first calibration phase to calibrate the clock signal against the reference signal and initially tune the clock signal to a desired frequency, and is reconfigurable for entering a second calibration phase only upon receiving the reference signal to maintain the clock signal at the desired frequency, the reference signal being generated on a periodic basis independent of any detected frequency drift; wherein the programmable calibration logic is further configurable for entering a touch sensing phase and generating the control signal for the local oscillator circuit in an absence of the reference signal when the reference signal is not being generated; and wherein the programmable calibration logic is configured to perform the first calibration phase by approximating a number of cycles of the desired frequency in one cycle of a reference signal by multiplying a programmable value and a granularity factor, the granularity, factor for reducing a number of bits in the programmable value while maintaining a reduced but sufficient precision in the approximated number of cycles, and iteratively adjusting an oscillator tuning value in accordance with a difference between a number of cycles of a measured oscillator frequency in one cycle of the reference signal and the approximated number of cycles. - View Dependent Claims (26, 27, 28, 29)
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Specification