Proximity sensing with soft-synchronization to noise
An input device includes a capacitive proximity sensor and a processing system. The capacitive proximity sensor includes a multitude of transmitter electrodes and a multitude of receiver electrodes for proximity sensing in a sensing region. The processing system is configured to obtain a noisy sensor signal from the capacitive proximity sensor, extract a spike train in the noisy sensor signal, synchronize a pulse output of a pulse-generating circuit onto the spike train, and triggered by a first of a multitude of pulses of the pulse output, perform a first capacitive proximity sensing.
1. An input device, comprising:
a capacitive proximity sensor comprising a plurality of transmitter electrodes and a plurality of receiver electrodes for proximity sensing in a sensing region;
a processing system configured to:
obtain a noisy sensor signal from the capacitive proximity sensor;
extract a spike train in the noisy sensor signal comprising:
rectifying the noisy sensor signal to produce an absolute value of the noisy sensor signal; and
thresholding the noisy sensor signal, after the rectifying;
synchronize a pulse output of a pulse-generating circuit onto the spike train; and
initiate a first capacitive proximity sensing based on a first pulse of the pulse output.
2. The input device of claim 1 , wherein the first capacitive proximity sensing comprises:
driving at least one of the plurality of transmitter electrodes with a sensing signal,
simultaneously with the driving, obtaining a resulting signal from at least one of the plurality of receiver electrodes, and
process the resulting signal to determine a presence of an input object in the sensing region.
3. The input device of claim 2 , wherein initiating the first capacitive proximity sensing based on the first pulse of the pulse output comprises:
implementing a specified delay, prior to emitting the sensing signal.
4. The input device of claim 1 , further comprising:
a display screen overlapping the sensing region.
5. The input device of claim 4 , wherein the display screen is an organic light-emitting diode (OLED) display.
6. The input device of claim 1 , wherein the capacitive proximity sensor is a metal mesh sensor.
7. The input device of claim 1 , wherein the pulse-generating circuit comprises a phase-locked loop.
8. The input device of claim 1 , wherein the noisy sensor signal is a spatial average signal of the plurality of receiver electrodes.
9. The input device of claim 1 , wherein the noisy sensor signal is a touch signal obtained from one of the plurality of receiver electrodes in proximity to the input object.
10. The input device of claim 1 , further comprising:
determining that the pulse output is not synchronized to the spike train; and
based on the determination:
preventing performing a second capacitive proximity sensing.
11. A processing system, comprising:
circuitry configured to:
obtain a noisy sensor signal from a capacitive proximity sensor interfacing with the circuitry of the processing system,
wherein the capacitive proximity sensor comprises a plurality of transmitter electrodes and a plurality of receiver electrodes for proximity sensing in a sensing region;
extract a spike train in the noisy sensor signal comprising:
rectifying the noisy sensor signal to produce an absolute value of the noisy sensor signal, and
thresholding the noisy sensor signal, after the rectifying;
synchronize a pulse output of a pulse-generating circuit onto the spike train; and
initiate a first capacitive proximity sensing based on a first pulse of the pulse output.
12. The processing system of claim 11 , wherein the pulse-generating circuit comprises a phase-locked loop.
13. A method of operating an input device, comprising:
obtaining a noisy sensor signal from a capacitive proximity sensor;
extracting a spike train in the rectified noisy sensor signal comprising:
rectifying the noisy sensor signal to produce an absolute value of the noisy sensor signal, and
thresholding the noisy sensor signal, after the rectifying;
synchronizing a pulse output of a pulse-generating circuit onto the spike train; and
initiating a first capacitive proximity sensing based on a first pulse of the pulse output.
14. The method of claim 13 , wherein the first capacitive sensing comprises:
driving at least one transmitter electrode of the capacitive proximity sensor with a sensing signal;
simultaneously with the driving, obtaining a resulting signal on at least one receiver electrode of the capacitive proximity sensor; and
processing the resulting signal to determine a presence of an input object at the capacitive proximity sensor.
15. The method of claim 13 , wherein initiating the first capacitive proximity sensing based on the first pulse of the pulse output comprises:
implementing a specified delay, prior to emitting the sensing signal.
16. The method of claim 13 , wherein the noisy sensor signal is a spatial average signal of a plurality of electrodes of the capacitive proximity sensor.
17. The method of claim 13 , wherein the noisy sensor signal is a touch signal obtained from a receiver electrode in proximity to the input object.
18. The method of claim 13 , further comprising:
determining that the pulse output is not synchronized to the spike train; and
based on the determination:
preventing performing a second capacitive proximity sensing.