Noise detection for a capacitance sensing panel
View Patent ↗An embodiment of a method for detecting noise for a capacitance sensing panel may comprise generating an input signal based on a noise signal, performing a series of measurements for measuring capacitances from a capacitive sensor sensitive to the noise signal, and controlling timing for at least one of the subconversions based on the input signal.
1. A method, comprising:
at a device with a touch sensitive display comprising a plurality of capacitive sensors:
generating a sensitivity window that defines a time duration for performing at least one noise-sensitive operation;
receiving a reject signal while performing a series of measurements to measure capacitances of a capacitive sensor of the plurality of capacitive sensors;
when the reject signal is received during the sensitivity window and the reject signal exceeds a predetermined threshold, controlling timing for at least one capacitance measurement of the series of measurements based on the reject signal and the sensitivity window; and
when the reject signal is received outside of the sensitivity window or the reject signal does not exceed the predetermined threshold, ignoring the reject signal.
2. The method of claim 1 , wherein each measurement of the series of measurements is a subconversion.
3. The method of claim 1 , wherein controlling the timing comprises aborting the at least one capacitance measurement at a time indicated by the reject signal.
4. The method of claim 3 , wherein the at least one noise-sensitive operation comprises the at least one capacitance measurement; and
wherein controlling the timing comprises aborting the at least one capacitance measurement in response to detecting that the reject signal is asserted during the time duration indicated by the sensitivity window.
5. The method of claim 1 , further comprising generating a start signal in accordance with a determination that the reject signal no longer exceeds the predetermined threshold.
6. The method of claim 5 , wherein the start signal comprises a periodic pulse train, and wherein each pulse of the periodic pulse train indicates a time for initiating a measurement of a capacitive sensor of the plurality of capacitive sensors.
7. An apparatus, comprising:
a first input configured to generate a sensitivity window that defines a time duration for performing at least one noise-sensitive operation;
a capacitive sensor sensitive to a noise signal; and
a sequencer coupled with the first input and the capacitive sensor, wherein the sequencer is configured to receive a reject signal while performing a series of measurements to measure capacitances of a capacitive sensor of the plurality of capacitive sensors, and configured to:
when the reject signal is received during the sensitivity window and the reject signal exceeds a predetermined threshold, control timing for at least one capacitance measurement of the series of measurements based on the reject signal and the sensitivity window; and
when the reject signal is received outside of the sensitivity window or the reject signal does not exceed the predetermined threshold, ignore the reject signal.
8. The apparatus of claim 7 , wherein each measurement of the series of measurements is a subconversion.
9. The apparatus of claim 7 , wherein the sequencer is configured to control the timing of the at least one measurement by aborting the at least one capacitance measurement at a time indicated by the reject signal.
10. The apparatus of claim 9 , wherein the sequencer is further configured to:
abort the at least one capacitance measurement in response to detecting that the reject signal is asserted during the time duration indicated by the sensitivity window, wherein the at least one noise-sensitive operation comprises the at least one capacitance measurement.
11. The apparatus of claim 7 , further comprising an interval discriminator circuit coupled with the sequencer, wherein the interval discriminator circuit is configured to generate a start signal in accordance with a determination that the reject signal no longer exceeds the predetermined threshold.
12. The apparatus of claim 11 , wherein the start signal comprises a periodic pulse train, and wherein each pulse of the periodic pulse train indicates a time for initiating a measurement of a capacitive sensor of the plurality of capacitive sensors.
13. An apparatus, comprising:
a capacitive sense array comprising a plurality of capacitive sensors, wherein the capacitive sense array is configured to detect a touch object; and
a processing device coupled to the capacitive sense array, the processing device configured to:
generate a sensitivity window that defines a time duration for performing at least one noise-sensitive operation;
receive a reject signal while performing a series of measurements to measure capacitances of a capacitive sensor of the plurality of capacitive sensors;
when the reject signal is received during the sensitivity window and the reject signal exceeds a predetermined threshold, control timing for at least one capacitance measurement of the series of measurements based on the reject signal and the sensitivity window; and
when the reject signal is received outside of the sensitivity window or the reject signal does not exceed the predetermined threshold, ignore the reject signal.
14. The apparatus of claim 13 , wherein each measurement of the series of measurements is a subconversion.
15. The apparatus of claim 13 , wherein controlling the timing comprises aborting the at least one capacitance measurement at a time indicated by the reject signal.
16. The apparatus of claim 15 , wherein the at least one noise-sensitive operation comprises the at least one capacitance measurement; and
wherein controlling the timing comprises aborting the at least one measurement in response to detecting that the reject signal is asserted during the time duration indicated by the sensitivity window.