Calibration of multiple analog front-ends

1. A method comprising:

coupling receiver circuitry of a processing system with a capacitive sensor comprising a plurality of sensor electrodes, the receiver circuitry comprising a plurality of analog-to-digital converters (ADCs), each ADC of the plurality of ADCs coupled with one or more respective sensor electrodes of the plurality of sensor electrodes;

while sensing signals are not provided by transmitter circuitry of the processing system, acquiring measurements using each ADC of the plurality of ADCs; and

storing, for each ADC of the plurality of ADCs, based on the acquired measurements, an offset mismatch value in a memory of the processing system,

wherein the processing system is operable to apply the plurality of offset mismatch values to capacitive measurements acquired using the plurality of ADCs.

2. The method of claim 1 , wherein each offset mismatch value of the plurality of offset mismatch values corresponds to a respective ADC of the plurality of ADCs.

3. The method of claim 1 , wherein the capacitive measurements acquired using the plurality of ADCs comprise baseline capacitive measurements.

4. The method of claim 3 , wherein applying the plurality of offset mismatch values to the capacitive measurements comprises:

for a first ADC of the plurality of ADCs, subtracting a first offset mismatch value corresponding to the first ADC from a first baseline capacitive measurement acquired by the first ADC.

5. The method of claim 1 , further comprising:

disabling at least a portion of the transmitter circuitry, wherein the transmitter circuitry comprises at least one of: a sensor electrode transmitter, a guard amplifier, and a coarse background compensation transmitter.

6. The method of claim 1 , further comprising:

coupling, while a calibration capacitor is set to a first non-zero capacitance value, each ADC of the plurality of ADCs to the calibration capacitor to acquire a plurality of first measurements;

coupling, while the calibration capacitor is set to a second non-zero capacitance value, each ADC of the plurality of ADCs to the calibration capacitor to acquire a plurality of second measurements; and

determining, using the first measurements and the second measurements, a plurality of gain mismatch values corresponding to the plurality of ADCs,

wherein the processing system is operable to apply the plurality of gain mismatch values to capacitive measurements acquired using the plurality of ADCs.

7. The method of claim 6 , further comprising:

applying the plurality of gain mismatch values to the capacitive measurements after applying the plurality of offset mismatch values to the capacitive measurements.

8. A processing system comprising:

transmitter circuitry configured to drive sensing signals onto a plurality of sensor electrodes; and

receiver circuitry comprising a plurality of analog-to-digital converters (ADCs), each ADC of the plurality of ADCs coupled with one or more respective sensor electrodes of the plurality of sensor electrodes, wherein the receiver circuitry is configured to:

while the sensing signals are not provided by the transmitter circuitry, acquire measurements using each ADC of the plurality of ADCs;

store, for each ADC of the plurality of ADCs, based on the acquired measurements, an offset mismatch value in a memory; and

apply the plurality of offset mismatch values to capacitive measurements acquired using the plurality of ADCs.

9. The processing system of claim 8 , wherein each offset mismatch value of the plurality of offset mismatch values corresponds to a respective ADC of the plurality of ADCs.

10. The processing system of claim 8 , wherein the capacitive measurements acquired using the plurality of ADCs comprise baseline capacitive measurements.

11. The processing system of claim 10 , wherein applying the plurality of offset mismatch values to the capacitive measurements comprises:

for a first ADC of the plurality of ADCs, subtracting a first offset mismatch value corresponding to the first ADC from a first baseline capacitive measurement acquired by the first ADC.

12. The processing system of claim 8 , wherein the transmitter circuitry comprises at least one of: a sensor electrode transmitter, a guard amplifier, and a coarse background compensation transmitter.

13. The processing system of claim 8 , wherein the receiver circuitry is further configured to:

couple, while a calibration capacitor is set to a first non-zero capacitance value, each ADC of the plurality of ADCs to the calibration capacitor to acquire a plurality of first measurements;

couple, while the calibration capacitor is set to a second non-zero capacitance value, each ADC of the plurality of ADCs to the calibration capacitor to acquire a plurality of second measurements;

determine, using the first measurements and the second measurements, a plurality of gain mismatch values corresponding to the plurality of ADCs; and

apply the plurality of gain mismatch values to the capacitive measurements acquired using the plurality of ADCs.

14. The processing system of claim 13 , wherein applying the plurality of gain mismatch values to the capacitive measurements is performed after applying the plurality of offset mismatch values to the capacitive measurements.

15. A method comprising:

coupling receiver circuitry of a processing system with a capacitive sensor comprising a plurality of sensor electrodes, the receiver circuitry comprising a plurality of analog-to-digital converters (ADCs), each ADC of the plurality of ADCs coupled with one or more respective sensor electrodes of the plurality of sensor electrodes;

for each ADC of the plurality of ADCs:

coupling, while a respective calibration capacitor of the ADC is set to a first non-zero capacitance value, the ADC to the calibration capacitor to acquire a first measurement;

coupling, while a respective calibration capacitor of the ADC is set to a second non-zero capacitance value, the ADC to the calibration capacitor to acquire a second measurement; and

determining, using the first measurement and the second measurement, a gain mismatch value respectively corresponding to the ADC,

wherein the processing system is operable to apply the gain mismatch value to capacitive measurements acquired using the ADC.

16. The method of claim 15 , further comprising:

while acquiring the first measurements and the second measurements, operating transmitter circuitry of the processing system in a predetermined state, wherein the predetermined state is selected based on a dynamic range of the receiver circuitry.

17. The method of claim 16 , wherein the dynamic range of the receiver circuitry is insufficient to support an implementation in which driving one or more sensor electrodes using the transmitter circuitry causes clipping to occur in the receiver circuitry,

wherein the predetermined state comprises enabling transmitters of the transmitter circuitry.

18. The method of claim 16 , wherein the dynamic range of the receiver circuitry is sufficient to support an implementation in which driving one or more sensor electrodes using the transmitter circuitry does not cause clipping to occur in the receiver circuitry,

wherein the predetermined state comprises disabling transmitters of the transmitter circuitry.

19. The method of claim 15 , wherein determining the plurality of gain mismatch values corresponding to the plurality of ADCs comprises:

for each ADC of the plurality of ADCs, determining a respective difference value between a corresponding first measurement and a corresponding second measurement, wherein a plurality of difference values are determined; and

determining an average difference value using the plurality of difference values, wherein the plurality of gain mismatch values are determined using the average difference value and the plurality of difference values.

20. The method of claim 19 , wherein determining the plurality of gain mismatch values comprises:

determining a plurality of normalized difference values by dividing each of the plurality of difference values by the average difference value, and

wherein applying the plurality of gain mismatch values comprises scaling the capacitive measurements acquired using the plurality of ADCs by the normalized difference values.