Dynamic mode switching for fast touch response

1. A method comprising:

performing a first scan of a first set of electrodes of a touch-sensing surface, wherein the first set of electrodes comprises only row electrodes or only column electrodes of the touch-sensing surface, wherein performing the first scan comprises measuring a self capacitance for each electrode in the first set of electrodes;

determining a presence of at least one conductive object proximate to the touch-sensing surface based on the first scan;

repeating the performing the first scan until the at least one conductive object is proximate to the touch-sensing surface;

when the at least one conductive object is proximate to the touch-sensing surface based on the first scan, performing a second scan of a second set of electrodes of the touch-sensing surface, wherein the second set of electrodes comprises the other one of only the column electrodes or only the row electrodes of the touch-sensing surface, wherein performing the second scan comprises measuring a self capacitance for each electrode in the second set of electrodes;

in response to determining the presence of the at least one conductive object, performing a third scan of a third set of electrodes of the touch-sensing surface, wherein performing the third scan comprises measuring a mutual capacitance between at least one pair of electrodes of the third set of electrodes; and

repeating the performing the third scan without repeating the performing the first scan and the second scan until the at least one conductive object is no longer proximate to the touch-sensing surface.

2. The method of claim 1 , wherein measuring the self capacitance for each electrode in the first set of electrodes comprises:

for each electrode in the first set,

charging the respective electrode with a capacitance sensor; and

discharging the respective electrode with the capacitance sensor, wherein the determining the presence comprises detecting a change in a rate of charge of the respective electrode when the presence of the at least one conductive object is proximate to the touch-sensing surface.

3. The method of claim 1 , wherein the third set of electrodes comprises all the row electrodes and all the column electrodes.

4. The method of claim 1 , further comprising determining a possible location of the at least one conductive object based on the first scan and the second scan, and wherein the third scan is a resolve scan to identify an actual location of the at least one conductive object.

5. The method of claim 1 , further comprising determining a possible location of the at least one conductive object based on the first scan and the second scan, and wherein the third set of electrodes comprises electrodes adjacent to the possible location of the at least one conductive object at the touch-sensing surface.

6. The method of claim 1 , further comprising determining a possible location of the at least one conductive object based on the first scan and the second scan, and wherein each of the electrodes of the third set of electrodes intersects another electrode within a threshold distance from the possible location of the at least one conductive object at the touch-sensing surface.

7. The method of claim 1 , wherein performing the first scan comprises measuring the self capacitance of the first set of electrodes at a single sense channel.

8. The method of claim 1 , wherein the first set of electrodes comprises at least one measured electrode and a plurality of non-measured electrodes, and wherein performing the first scan comprises driving each of the non-measured electrodes with a shield drive signal.

9. The method of claim 1 , wherein the first set of electrodes is divided into a plurality of zones, wherein each of the plurality of zones comprises a subset of electrodes from the first set of electrodes, and wherein performing first scan comprises scanning each of the plurality of zones according to a predetermined sequence.

10. The method of claim 9 , wherein electrodes of a first zone of the plurality of zones are interleaved with electrodes of a second zone of the plurality of zones.

11. The method of claim 1 , wherein at least one electrode of the first set of electrodes is included in the second set of electrodes.

12. A touch sensor controller comprising:

processing logic circuitry;

a plurality of inputs configured to couple the processing logic circuitry with each of a plurality of electrodes of a touch-sensing surface; and

a capacitance sensor coupled with the plurality of inputs, wherein the capacitance sensor is configured to:

perform a first scan of a first set of the plurality electrodes of the touch-sensing surface to determine a presence of at least one conductive object proximate to the touch-sensing surface, the first set comprising only row electrodes or only column electrodes of the touch-sensing surface, the first scan being a self-capacitance scan,

repeat the first scan until the at least one conductive object is proximate to the touch-sensing surface,

when the at least one when the at least one conductive object is proximate to the touch-sensing surface based on the first scan, perform a second scan of a second set of the plurality of electrodes, the second set of electrodes comprising the other one of only the column electrodes or only the row electrodes of the touch-sensing surface, and the second scan being a self-capacitance scan,

in response to determining the presence of the at least one conductive object, perform a third scan of a third set of the plurality of electrodes of the touch-sensing surface, and

repeat the third scan without repeating the first scan and the second scan until the at least one conductive object is no longer proximate to the touch-sensing surface.

13. The touch sensor controller of claim 12 , wherein the first set of electrodes and the second set of electrodes comprise all the row electrodes and all the column electrodes and the third set comprises less than all the row electrodes and less than all the column electrodes.

14. The touch sensor controller of claim 12 , wherein the capacitance sensor comprises an amplifier coupled to a voltage reference and a respective one of the first set of the plurality of electrodes during the first scan, wherein the capacitance sensor is configured to charge and discharge the respective one of the first set of the plurality of electrodes during a plurality of charge and discharge cycles, and wherein the capacitance sensor is configured to detect a change in a rate of charge of the respective one of the first set of the plurality of electrodes when the presence of the at least one conductive object is proximate to the touch-sensing surface.

15. A touch-sensor controller comprising:

a plurality of inputs configured to couple with each of a plurality of electrodes of a touch-sensing surface; and

a capacitance sensor coupled with the plurality of inputs, wherein the capacitance sensor is configured to perform a first self-capacitance scan of a first set of the plurality of electrodes to detect a presence of a conductive object proximate to the touch-sensing surface, wherein the first set comprises only row electrodes or only column electrodes of the plurality of electrodes, wherein the capacitance sensor is further configured to repeat the first self-capacitance scan until the presence of the conductive object is proximate to the touch-sensing surface, wherein the capacitance sensor is further configured to perform a second self-capacitance scan of a second set of the plurality of electrodes to determine a possible location of the conductive object when the presence of the conductive object is proximate to the touch-sensing surface based on the first scan, wherein the second set comprises the other one of only the column electrodes or only the row electrodes of the touch-sensing surface, wherein the capacitance sensor is further configured to perform a mutual capacitance scan between at least one pair of the plurality of electrodes to determine an actual position of the conductive object proximate to the touch-sensing surface, and wherein the capacitance sensor is further configured to repeat the mutual capacitance scan without repeating the first self-capacitance scan and the second self-capacitance scan until the conductive object is no longer proximate to the touch-sensing surface.

16. The touch-sensor controller of claim 15 , wherein the capacitance sensor is further configured to identify a plurality of possible locations of one or more conductive objects based on the first self-capacitance scan and the second self-capacitance scan and to identify at least one of a plurality of possible locations as an actual location of the one or more conductive objects based on the mutual capacitance scan.

17. The touch-sensor controller of claim 15 , wherein the capacitance sensor is further configured to perform the mutual capacitance scan on electrodes adjacent to the possible location of the conductive object at the touch-sensing surface based on the first self-capacitance scan and the second self-capacitance scan.

18. The touch-sensor controller of claim 15 , wherein the capacitance sensor comprises an amplifier coupled to a voltage reference and a respective one of the first set of the plurality of electrodes during the first self-capacitance scan, wherein the capacitance sensor is configured to charge and discharge the respective one of the plurality of electrodes during a plurality of charge and discharge cycles, and wherein the capacitance sensor is configured to detect a change in a rate of charge of the respective one of the plurality of electrodes when the presence of the at least one conductive object is proximate to the touch-sensing surface.