Applying a signal to a touch sensor
In one embodiment, a non-transitory computer-readable medium comprising logic is configured to, when executed by one or more processors, cause the one or more processors to perform operations comprising measuring samples from a touch sensor. Each sample is measured by determining, based on a first pattern of polarities, a polarity of a charging signal to be applied to an electrode of the touch sensor, the first pattern of polarities based on a signal associated with a noise source; applying the charging signal to the electrode, the charging signal, as applied, having the polarity determined based on the first pattern of polarities; and measuring a received signal from the touch sensor, the received signal resulting, at least in part, from the charging signal applied to the electrode. The operations comprise determining whether a touch event has occurred at the electrode by analyzing the received signals from the samples.
1. A non-transitory computer-readable medium comprising logic, the logic configured to, when executed by one or more processors, cause the one or more processors to perform operations comprising:
measuring a plurality of samples from a touch sensor, wherein measuring each sample comprises:
determining, based on a first pattern of polarities, a polarity of a charging signal to be applied to an electrode of the touch sensor, the first pattern of polarities being based on a signal associated with a noise source;
applying the charging signal to the electrode of the touch sensor, the charging signal, as applied, having the polarity determined based on the first pattern of polarities; and
measuring a received signal from the touch sensor, the received signal resulting, at least in part, from the charging signal applied to the electrode; and
determining whether a touch event has occurred at a capacitive node formed at the electrode of the touch sensor by analyzing the received signals from the plurality of samples;
wherein the signal associated with the noise source is a periodic synchronization signal to which the periodic noise component is synchronized; and
wherein measuring the plurality of samples comprises:
measuring the first portion of the plurality of samples during consecutive periods of the synchronization signal;
delaying measurement of a sample for a period of the synchronization signal; and
measuring a second portion of the plurality of samples during consecutive periods of the synchronization signal following the delay.
2. The non-transitory computer-readable medium of claim 1 , wherein the plurality of samples are measured at a same frequency and phase as the synchronization signal such that a sample is measured during consecutive half-periods of the periodic noise component.
3. The non-transitory computer-readable medium of claim 1 , wherein:
measuring the first portion of the plurality of samples comprises applying a plurality of charging signals based on the first pattern of polarities; and
measuring the second portion of the plurality of samples comprises applying a plurality of charging signals based on a second pattern of polarities.
4. The non-transitory computer-readable medium of claim 3 , wherein each polarity of the first pattern of polarities is opposite in polarity to each corresponding polarity of the second pattern of polarities.
5. The non-transitory computer-readable medium of claim 1 , wherein:
a display screen is synchronized to the synchronization signal; and
the periodic noise component is generated by the display screen.
6. The non-transitory computer-readable medium of claim 1 , wherein analyzing the received signals of the first portion of samples comprises:
summing the received signals of the first portion of samples to obtain a running sum;
dividing the running sum by a number of samples of the first portion to obtain a sampled result; and
conducting a comparison to compare the sampled result to a predetermined threshold; and
determining whether the touch event has occurred based on the comparison.
7. A method, comprising:
measuring a plurality of samples from a touch sensor, wherein measuring each sample comprises:
determining, based on a first pattern of polarities, a polarity of a charging signal to be applied to an electrode of the touch sensor, the first pattern of polarities being based on a signal associated with a noise source;
applying the charging signal to the electrode of the touch sensor, the charging signal, as applied, having the polarity determined based on the first pattern of polarities; and
measuring a received signal from the touch sensor, the received signal resulting, at least in part, from the charging signal applied to the electrode; and
determining whether a touch event has occurred at the electrode of the touch sensor by analyzing the received signals from the plurality of samples;
wherein the signal associated with the noise source is a periodic synchronization signal to which the periodic noise component is synchronized; and
wherein measuring the plurality of samples comprises:
measuring the first portion of the plurality of samples during consecutive periods of the synchronization signal;
delaying measurement of a sample for a period of the synchronization signal; and
measuring a second portion of the plurality of samples during consecutive periods of the synchronization signal following the delay.
8. The method of claim 7 , wherein the plurality of samples are measured at a same frequency and phase as the synchronization signal such that a sample is measured during consecutive half-periods of the periodic noise component.
9. The method of claim 7 , wherein measuring the first portion of the plurality of samples comprises applying a plurality of charging signals based on the first pattern of polarities, and measuring the second portion of the plurality of samples comprises applying a plurality of charging signals based on a second pattern of polarities.
10. The method of claim 9 , wherein each polarity of the first pattern of polarities is opposite in polarity to each corresponding polarity of the second pattern of polarities.
11. The method of claim 7 , wherein analyzing the received signals of the first portion of samples comprises:
summing the received signals of the first portion of samples to obtain a running sum;
dividing the running sum by a number of samples of the first portion to obtain a sampled result;
conducting a comparison to compare the sampled result to a predetermined threshold; and
determining whether the touch event has occurred based on the comparison.
12. An apparatus, comprising:
one or more processors; and
one or more memory units coupled to the one or more processors, the one or more memory units collectively storing logic configured to, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
measuring a plurality of samples from a touch sensor, wherein measuring each sample comprises:
determining, based on a first pattern of polarities, a polarity of a charging signal to be applied to an electrode of the touch sensor, the first pattern of polarities being based on a signal associated with a noise source;
applying the charging signal to the electrode of the touch sensor, the charging signal, as applied, having the polarity determined based on the first pattern of polarities; and
measuring a received signal from the touch sensor, the received signal resulting, at least in part, from the charging signal applied to the electrode; and
determining whether a touch event has occurred at the electrode of the touch sensor by analyzing the received signals from the plurality of samples;
wherein the signal associated with the noise source is a periodic synchronization signal to which a periodic noise component of the received signal is synchronized; and
wherein measuring the plurality of samples comprises:
measuring a first portion of the plurality of samples during consecutive periods of the synchronization signal;
delaying measurement of a sample for a period of the synchronization signal; and
measuring a second portion of the plurality of samples during consecutive periods of the synchronization signal following the delay.
13. The apparatus of claim 12 , wherein:
measuring the first portion of the plurality of samples comprises applying a plurality of charging signals based on the first pattern of polarities; and
measuring the second portion of the plurality of samples comprises applying a plurality of charging signals based on a second pattern of polarities.
14. The apparatus of claim 13 , wherein each polarity of the first pattern of polarities is opposite in polarity to each corresponding polarity of the second pattern of polarities.