Methods and apparatus for click detection on a force pad using dynamic thresholds

1. A method for measuring force on a force enabled input device having a touch surface, the method comprising:

detecting force information associated with an input object contacting the touch surface;

determining a push event in response to the force information being a monotonic increase to a first force level, the first force level being a sum of a dynamic push threshold value and a low baseline value;

detecting a peak force value of the push event, wherein the peak force value is greater than the first force level;

computing a dynamic release force level as an intermediate value using the first force level and a second force level, the intermediate value being in between and non-inclusive of the first force level and the second force level,

the second force level defined by the dynamic push threshold value subtracted from the peak force level;

thereafter determining a first release event when the force information decreases below the dynamic release force level; and

initiating a first type of user interface action associated with the input object based on a determination of the push event and the first release event.

2. The method of claim 1 , wherein the first type of user interface action comprises determining a virtual button click.

3. The method of claim 1 , further comprising initiating a second type of user interface action if the push event is determined and the first release event is not determined.

4. The method of claim 3 , wherein the second type of user interface action comprises one of:

a button down event; and

a click and hold event.

5. The method of claim 3 , further comprising modifying the second type of user interface action based on positional information for at least one input object translating across the touch surface.

6. The method of claim 5 , wherein translating comprises one of a dragging action and a scrolling action, and further wherein the at least one input object comprises one of: the same finger used to push and translate; and a first finger used to push and a second finger used to translate.

7. The method of claim 3 , further comprising terminating the second type of user interface action based on a subsequent determination of the release event.

8. The method of claim 1 , further comprising determining the low baseline value based on one of:

the detected force information for a first predetermined period of time; and

a local minimum immediately preceding the substantially monotonic increase in the measured force.

9. The method of claim 1 , further comprising determining the peak force value based on the detected force information for a second predetermined period of time following determining the push event.

10. The method of claim 9 , wherein the peak force value is substantially adjacent to the push event.

11. The method of claim 9 , wherein the peak force value corresponds to a local maximum value associated with the push event.

12. The method of claim 1 , wherein a level of applied force at which a second release event is declared is greater than the peak force value corresponding to the first release event.

13. The method of claim 1 , wherein the intermediate value is declared is one of an average value, a weighted average value, a median value, and a midpoint of the first force level and the second force level.

14. An input device comprising:

a force enabled touch pad having a touch surface; and

a processing system communicatively coupled to the touch pad, the processing system configured to:

detect force information associated with an input object contacting the touch surface;

determine a push event in response to the force information increasing monotonically to a first force level, the first force level being a sum of a dynamic push threshold value and a low baseline value;

detect a peak force value of the push event, wherein the peak force value is greater than the first force level;

compute a dynamic release force level as an intermediate value using the first force level and a second force level, the intermediate value being in between and non-inclusive of the first force level and the second force level,

the second force level defined by the dynamic push threshold value subtracted from the peak force level; and

thereafter determine a release event when the force information decreases below the dynamic release force level.

15. The input device of claim 14 , wherein the processing system is further configured to determine the low baseline value based on one of:

the detected force information for a first predetermined period of time; and

a local minimum immediately preceding the substantially monotonic increase in the measured force.

16. The input device of claim 14 , wherein the processing system is configured to determine the peak force value based on the detected force information for a second predetermined period of time following determining the push event.

17. The input device of claim 16 , wherein the peak force value is substantially adjacent to the push event.

18. The input device of claim 17 , wherein the peak force value corresponds to a local maximum value associated with the push event.

19. The input device of claim 14 , wherein a level of applied force at which a second release event is declared is greater than the peak force value corresponding to the first release event.

20. The input device of claim 14 , wherein the intermediate value is declared is one of an average value, a weighted average value, a median value, and a midpoint of the first force level and the second force level.