Apparatus and method for recognizing a gesture on a sensing device

1. A method, comprising:

detecting a presence of a first stationary conductive object at a sensing device;

detecting a presence of a second conductive object at the sensing device while the first conductive object is present at the sensing device;

detecting a tap of the second conductive object while the first stationary conductive object is present at the sensing device, wherein a time duration of the tap is less than a threshold time; and

recognizing a gesture based on the detected presence of the first stationary conductive object, the detected tap of the second conductive object, and a direction, along an axis, of a difference between a position of the first stationary conductive object and a position of the second conductive object,

wherein recognizing the gesture comprises:

recognizing a tap gesture of the second conductive object;

determining a first position of the second conductive object; and

recognizing a scroll gesture based on the presence of a first conductive object, the first position and the tap gesture.

2. The method of claim 1 , wherein recognizing the gesture comprises:

recognizing a scroll gesture based on the direction.

3. The method of claim 1 , wherein detecting each presence of the first and second conductive objects comprises determining a capacitance of the conductive object on the sensing device over time, and wherein recognizing the gesture is based on the capacitance of the sensing device at least a first time and a second time.

4. The method of claim 1 , wherein detecting the presence of the first and second conductive objects comprises:

determining a capacitance of each of a plurality of sensor elements of the sensing device; and

determining an average capacitance based on the capacitance of each of the plurality of sensor elements, wherein recognizing the gesture is based on the average capacitance.

5. An apparatus, comprising:

a sensing device having a plurality of sensor elements to detect presences of first and second conductive objects; and

a processing device coupled to the sensing device, wherein the processing device is operable to recognize a gesture based on the presences of the first and second conductive objects, wherein the processing device is operable to recognizing the gesture by detecting a tap of the second conductive object independent of a location of the first conductive object and while the first conductive object is substantially stationary in proximity to the sensing device, wherein a time duration of the tap is less than a threshold time, and wherein the processing device is further configured to recognize the gesture based on a direction, along an axis, of a difference between a position of the first substantially stationary conductive object and a position of the second conductive object,

wherein the processing device is operable to determine the position of the second conductive object, and to recognize a scroll gesture based on the presence of the first conductive object and the position of the second conductive object.

6. The apparatus of claim 5 , wherein the processing device comprises one or more capacitance sensors coupled to a plurality of sensor elements of the sensing device, and wherein the one or more capacitance sensors are operable to measure capacitance on each sensor element.

7. The apparatus of claim 6 , wherein each of the one or more capacitance sensors comprises a relaxation oscillator coupled to the plurality of sensor elements, wherein the relaxation oscillator comprises:

a current source to provide a charge current to the plurality of sensor elements:

a selection circuit coupled to the plurality of sensor elements and the current source, wherein the selection circuit is configured to sequentially select a sensor element of the plurality of sensor elements to provide the charge current and to measure the capacitance of each sensor element of the sensing device;

a comparator coupled to the current source and the selection circuit, wherein the comparator is configured to compare a voltage on the selected sensor element and a threshold voltage; and

a reset switch coupled to the comparator, current source, and selection circuit, wherein the reset switch is configured to reset the charge current on the selected sensor element, wherein the one or more capacitance sensor further comprises a digital counter is configured to count at least one of a frequency or a period of a relaxation oscillator output received from the relaxation oscillator.

8. The apparatus of claim 7 , further comprising a component external to the processing device, wherein the processing device is configured to send data to the component when the gesture is recognized.

9. The apparatus of claim 8 , wherein the component external to the processing device is at least one of a processor, a driver of a processor, or an embedded controller.

10. The apparatus of claim 8 , wherein the data is at least of a command or a signal.

11. The apparatus of claim 5 , wherein the conductive object is at least one of a finger or a stylus.

12. The apparatus of claim 5 , wherein the sensing device is at least one of a touch-sensor pad, or a touch-sensor slider.

13. An apparatus, comprising:

means for detecting presences of a first conductive object and a second conductive object on a sensing device;

means for detecting a tap of the second conductive object while the first conductive object is substantially stationary on the sensing device, wherein a time duration of the tap is less than a threshold time;

means for recognizing a gesture based on a direction, along an axis, of a difference between a position of the first conductive object that is substantially stationary and a position of the detected tap of the second conductive object;

means for determining the position of the second conductive object; and

means for recognizing a scroll gesture based on the presence of the first conductive object and the position of the second conductive object.

14. The apparatus of claim 13 , further comprising means for increasing a sensing surface area of the sensing device.