Reduced capacitive baseline shift via mixing period adjustments

1. A method comprising:

acquiring, responsive to a first capacitive sensing signal driven on a first group of one or more sensor electrodes, first capacitive measurements of resulting signals received by a second group of one or more sensor electrodes, wherein acquiring the first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period, the first capacitive sensing signal having a first sensing frequency; and

acquiring, responsive to a second capacitive sensing signal driven on a third group of one or more sensor electrodes, second capacitive measurements of resulting signals received by a fourth group of one or more sensor electrodes, wherein acquiring the second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period, the second capacitive sensing signal having a second sensing frequency,

wherein the second mixing period is different than the first mixing period and is selected such that a second average current value for the second capacitive measurements has a predefined relationship to a first average current value for the first capacitive measurements, the predefined relationship based on the first sensing frequency and the second sensing frequency.

2. The method of claim 1 , wherein according to the predefined relationship, the second average current value is substantially equal to the first average current value.

3. The method of claim 1 , wherein according to the predefined relationship, the second average current value has a substantially linear relation to the first average current value.

4. 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 to the second mixing period.

5. The method of claim 4 , 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.

6. 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.

7. The method of claim 6 , 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.

8. A processing system comprising:

a sensing module comprising sensing circuitry and configured to:

acquire, responsive to a first capacitive sensing signal driven on a first group of one or more sensor electrodes, first capacitive measurements of resulting signals received by a second group of one or more sensor electrodes, wherein acquiring the first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period, the first capacitive sensing signal having a first sensing frequency; and acquire, responsive to a second capacitive sensing signal driven on a third group of one or more sensor electrodes, second capacitive measurements of resulting signals received by a fourth group of one or more sensor electrodes, wherein acquiring the second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period, the second capacitive sensing signal having a second sensing frequency,

wherein the second mixing period is different than the first mixing period and is selected such that a second average current value for the second capacitive measurements has a predefined relationship to a first average current value for the first capacitive measurements, the predefined relationship based on the first sensing frequency and the second sensing frequency.

9. The processing system of claim 8 , wherein according to the predefined relationship, the second average current value is substantially equal to the first average current value.

10. The processing system of claim 8 , wherein according to the predefined relationship, the second average current value has a substantially linear relation to the first average current value.

11. The processing system of claim 8 , 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 to the second mixing period.

12. The processing system of claim 11 , 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.

13. The processing system of claim 8 , 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.

14. The processing system of claim 13 , 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.

15. 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:

acquire, responsive to a first capacitive sensing signal driven on a first group of one or more sensor electrodes, first capacitive measurements of resulting signals received by a second group of one or more sensor electrodes, wherein acquiring the first capacitive measurements comprises applying a first demodulation signal having a predefined first mixing period, the first capacitive sensing signal having a first sensing frequency;

acquire, responsive to a second capacitive sensing signal driven onto a third group of one or more sensor electrodes, second capacitive measurements of resulting signals received by a fourth group of one or more sensor electrodes, wherein acquiring the second capacitive measurements comprises applying a second demodulation signal having a predefined second mixing period, the second capacitive sensing signal having a second sensing frequency,

wherein the second mixing period is different than the first mixing period and is selected such that a second average current value for the second capacitive measurements has a predefined relationship to a first average current value for the first capacitive measurements, the predefined relationship based on the first sensing frequency and the second sensing frequency.

16. The input device of claim 15 , wherein according to the predefined relationship, the second average current value is substantially equal to the first average current value.

17. The input device of claim 15 , wherein according to the predefined relationship, the second average current value has a substantially linear relation to the first average current value.

18. The input device of claim 15 , 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 to the second mixing period.

19. The input device of claim 18 , 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.

20. The input device of claim 15 , 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.