Reduced capacitive baseline shift via mixing period adjustments

1. A method comprising:

driving, onto a first group of a plurality of sensor electrodes, a first capacitive sensing signal having a predefined first sensing frequency;

acquiring, based on the driven first capacitive sensing signal, first capacitive measurements of resulting signals received by a second group of the plurality of sensor electrodes, wherein acquiring first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period defined within a sensing period associated with the first sensing frequency;

driving, onto a third group of the plurality of sensor electrodes, a second capacitive sensing signal having a second sensing frequency different than the first sensing frequency; and

acquiring, based on the driven second capacitive sensing signal, second capacitive measurements of resulting signals received by a fourth group of the plurality of sensor electrodes,

wherein acquiring second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period within a sensing period associated with the second sensing frequency, the second mixing period different than the first mixing period, and

wherein the second mixing period is selected such that a second average current value for the second capacitive measurements has a substantially linear relation to a first average current value for the first capacitive measurements, the linear relation based on the first sensing frequency and the second sensing frequency.

2. The method of claim 1 , wherein the second mixing period is selected such that a second average current value for the second capacitive measurements is substantially equal to a first average current value for the first capacitive measurements.

3. The method of claim 1 , wherein each sensing period comprises a positive sensing half-cycle and a negative sensing half-cycle, wherein the positive sensing half-cycle and the negative sensing half-cycle each have a length corresponding to the first mixing period or the second mixing period.

4. The method of claim 3 , wherein the first demodulation signal and the second demodulation signal are three-level demodulation signals having a positive level, a negative level, and a zero level,

wherein applying the first demodulation signal and applying the second demodulation signal each comprises:

applying the positive level during the positive sensing half-cycle;

applying the negative level during the negative sensing half-cycle; and

applying the zero level during a predefined period within the sensing period between the positive sensing half-cycle and the negative sensing half-cycle.

5. The method of claim 1 , wherein the first sensing frequency and the second sensing frequency are included in a predefined plurality of sensing frequencies,

wherein the first mixing period and the second mixing period are included in a predefined plurality of mixing periods selected based on an identified one or more slowest sensor electrodes of the plurality of sensor electrodes.

6. The method of claim 5 , wherein the predefined plurality of mixing periods are further selected based on one or more fastest sensing frequencies of the predefined plurality of sensing frequencies.

7. A processing system comprising:

a sensing module comprising sensing circuitry and configured to:

drive, onto a first group of a plurality of sensor electrodes, a first capacitive sensing signal having a predefined first sensing frequency;

acquire, based on the driven first capacitive sensing signal, first capacitive measurements of resulting signals received by a second group of the plurality of sensor electrodes, wherein acquiring first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period defined within a sensing period associated with the first sensing frequency;

drive, onto a third group of the plurality of sensor electrodes, a second capacitive sensing signal having a second sensing frequency different than the first sensing frequency; and

acquire, based on the driven second capacitive sensing signal, second capacitive measurements of resulting signals received by a fourth group of the plurality of sensor electrodes,

wherein acquiring second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period within a sensing period associated with the second sensing frequency, the second mixing period different than the first mixing period, and

wherein the second mixing period is selected such that a second average current value for the second capacitive measurements has a substantially linear relation to a first average current value for the first capacitive measurements, the linear relation based on the first sensing frequency and the second sensing frequency.

8. The processing system of claim 7 , wherein the second mixing period is selected such that a second average current value for the second capacitive measurements is substantially equal to a first average current value for the first capacitive measurements.

9. The processing system of claim 7 , wherein each sensing period comprises a positive sensing half-cycle and a negative sensing half-cycle, wherein the positive sensing half-cycle and the negative sensing half-cycle each have a length corresponding to the first mixing period or the second mixing period.

10. The processing system of claim 9 , wherein the first demodulation signal and the second demodulation signal are three-level demodulation signals having a positive level, a negative level, and a zero level,

wherein applying the first demodulation signal and applying the second demodulation signal each comprises:

applying the positive level during the positive sensing half-cycle;

applying the negative level during the negative sensing half-cycle; and

applying the zero level during a predefined period within the sensing period between the positive sensing half-cycle and the negative sensing half-cycle.

11. The processing system of claim 7 , wherein the first sensing frequency and the second sensing frequency are included in a predefined plurality of sensing frequencies,

wherein the first mixing period and the second mixing period are included in a predefined plurality of mixing periods selected based on an identified one or more slowest sensor electrode of the plurality of sensor electrodes.

12. The processing system of claim 11 , wherein the predefined plurality of mixing periods are further selected based on one or more fastest sensing frequencies of the predefined plurality of sensing frequencies.

13. An input device comprising:

a plurality of sensor electrodes; and

a processing system coupled with the plurality of sensor electrodes, wherein the processing system is configured to:

drive, onto a first group of a plurality of sensor electrodes, a first capacitive sensing signal having a predefined first sensing frequency;

acquire, based on the driven first capacitive sensing signal, first capacitive measurements of resulting signals received by a second group of the plurality of sensor electrodes, wherein acquiring first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period defined within a sensing period associated with the first sensing frequency;

drive, onto a third group of the plurality of sensor electrodes, a second capacitive sensing signal having a second sensing frequency different than the first sensing frequency; and

acquire, based on the driven second capacitive sensing signal, second capacitive measurements of resulting signals received by a fourth group of the plurality of sensor electrodes,

wherein acquiring second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period within a sensing period associated with the second sensing frequency, the second mixing period different than the first mixing period, and

wherein the second mixing period is selected such that a second average current value for the second capacitive measurements has a substantially linear relation to a first average current value for the first capacitive measurements, the linear relation based on the first sensing frequency and the second sensing frequency.

14. The input device of claim 13 , wherein the second mixing period is selected such that a second average current value for the second capacitive measurements is substantially equal to a first average current value for the first capacitive measurements.

15. The input device of claim 13 , wherein each sensing period comprises a positive sensing half-cycle and a negative sensing half-cycle, wherein the positive sensing half-cycle and the negative sensing half-cycle each have a length corresponding to the first mixing period or the second mixing period.

16. The input device of claim 15 , wherein the first demodulation signal and the second demodulation signal are three-level demodulation signals having a positive level, a negative level, and a zero level,

wherein applying the first demodulation signal and applying the second demodulation signal each comprises:

applying the positive level during the positive sensing half-cycle;

applying the negative level during the negative sensing half-cycle; and

applying the zero level during a predefined period within the sensing period between the positive sensing half-cycle and the negative sensing half-cycle.

17. The input device of claim 13 , wherein the first sensing frequency and the second sensing frequency are included in a predefined plurality of sensing frequencies,

wherein the first mixing period and the second mixing period are included in a predefined plurality of mixing periods selected based on an identified one or more slowest sensor electrodes of the plurality of sensor electrodes.