Stylus signal detection and demodulation architecture
First Claim
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1. A method of detecting a presence of a stylus signal generated by an asynchronous external stylus on a touch input device, the method comprising:
- receiving the stylus signal generated by the asynchronous external stylus,wherein the asynchronous external stylus generates the stylus signal asynchronously from the touch input device, and the stylus signal generated by the asynchronous external stylus has a beginning time and an end time;
determining a first time value corresponding to the beginning time of the received stylus signal based on an analysis of the received stylus signal;
determining a second time value corresponding to the end time of the received stylus signal based on the analysis of the received stylus signal, wherein determining the second time value includes;
performing a spectral analysis of the received stylus signal, the spectral analysis comprising;
performing a plurality of estimates of a magnitude of the stylus signal, each estimate of the magnitude corresponding to a transform of the plurality of single frequency Fourier transforms; and
determining a peak magnitude from the plurality of estimates of the magnitude; and
determining a time at which the peak magnitude occurred,wherein determining the time at which the peak magnitude occurred includes;
determining a third time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a first pre-determined threshold;
determining a fourth time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a second pre-determined threshold; and
calculating a time centroid based on the determined third value of time and the determined fourth value of time; and
demodulating the stylus signal based on the determined first time value and second time value.
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Abstract
A touch input device configured to detect stylus signals generated by an external stylus is provided. The touch input device includes a plurality of stylus signal detectors that can receive the stylus signal and estimate the start and end time of the stylus signal in order to facilitate windowed demodulation of signal. The start and end times are then used to facilitate a windowed demodulation of the stylus signal.
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Citations
12 Claims
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1. A method of detecting a presence of a stylus signal generated by an asynchronous external stylus on a touch input device, the method comprising:
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receiving the stylus signal generated by the asynchronous external stylus, wherein the asynchronous external stylus generates the stylus signal asynchronously from the touch input device, and the stylus signal generated by the asynchronous external stylus has a beginning time and an end time; determining a first time value corresponding to the beginning time of the received stylus signal based on an analysis of the received stylus signal; determining a second time value corresponding to the end time of the received stylus signal based on the analysis of the received stylus signal, wherein determining the second time value includes; performing a spectral analysis of the received stylus signal, the spectral analysis comprising; performing a plurality of estimates of a magnitude of the stylus signal, each estimate of the magnitude corresponding to a transform of the plurality of single frequency Fourier transforms; and determining a peak magnitude from the plurality of estimates of the magnitude; and determining a time at which the peak magnitude occurred, wherein determining the time at which the peak magnitude occurred includes; determining a third time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a first pre-determined threshold; determining a fourth time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a second pre-determined threshold; and calculating a time centroid based on the determined third value of time and the determined fourth value of time; and demodulating the stylus signal based on the determined first time value and second time value. - View Dependent Claims (2, 3, 4)
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5. An apparatus for detecting a presence of stylus signals generated by an asynchronous external stylus on a touch input device, the apparatus comprising:
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receive circuitry capable of receiving a stylus signal generated by the external asynchronous stylus, wherein the asynchronous external stylus generates the stylus signal asynchronously from the touch input device, and the stylus signal generated by the external asynchronous stylus has a beginning time and an end time; a stylus signal beginning and end time detector coupled to the receive circuitry and configured to determine a first time value corresponding to the beginning time of the stylus signal based on an analysis of the received stylus signal and determine a second time value corresponding to the end time of the stylus signal based on the analysis of the received stylus signal, wherein determining the second time value includes; performing a spectral analysis of the received stylus signal, the spectral analysis comprising; performing a plurality of estimates of a magnitude of the stylus signal, each estimate of the magnitude corresponding to a transform of the plurality of single frequency Fourier transforms; and determining a peak magnitude from the plurality of estimates of the magnitude; and determining a time at which the peak magnitude occurred, wherein determining the time at which the peak magnitude occurred includes; determining a third time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a first pre-determined threshold; determining a fourth time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a second pre-determined threshold; and calculating a time centroid based on the determined third value of time and the determined fourth value of time; and a demodulator coupled to the receive circuitry and configured to demodulate the stylus signal based on the determined first time value and second time value. - View Dependent Claims (6, 7, 8)
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9. A non-transitory computer readable storage medium having stored thereon a set of instructions for detecting and demodulating a stylus signal generated by an asynchronous external stylus, that when executed by a processor causes the processor to:
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receive a stylus signal generated by an asynchronous external stylus, wherein the asynchronous external stylus generates the stylus signal asynchronously from the touch input device, and the stylus signal generated by the asynchronous external stylus has a beginning time and an end time; determine a first time value corresponding to the beginning time of the received stylus signal based on an analysis of the received stylus signal; determine a second time value corresponding to the end time of the received stylus signal based on the analysis of the received stylus signal, wherein determining the second time value includes; performing a spectral analysis of the received stylus signal, the spectral analysis comprising; performing a plurality of estimates of a magnitude of the stylus signal, each estimate of the magnitude corresponding to a transform of the plurality of single frequency Fourier transforms; and determining a peak magnitude from the plurality of estimates of the magnitude; and determining a time at which the peak magnitude occurred, wherein determining the time at which the peak magnitude occurred includes; determining a third time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a first pre-determined threshold; determining a fourth time value corresponding to when an estimate of the magnitude of the plurality of estimates of the magnitude crosses a second pre-determined threshold; and calculating a time centroid based on the determined third value of time and the determined fourth value of time; and demodulate the stylus signal based on the determined first time value and second time value. - View Dependent Claims (10, 11, 12)
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Specification