Capacitive sense touch device with hysteresis threshold

• US 8,487,912 B1
• Filed: 03/31/2008
• Issued: 07/16/2013
• Est. Priority Date: 02/01/2008
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Peterson, Jonathan
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): Chow, Yuk
• Application Number:
  US12/060,203
• Time in Patent Office: 1,933 Days
• Field of Search: 345173-175, 178/18.06
• US Class Current: 345/175
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 3/0227 Cooperation and interconnection of the input arrangement with other functional units of a computer G06F3/023 - G06F3/037 take precedence
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

In one embodiment, control circuitry receives an indication of a current position of an input object on a capacitive touch sense device. The control circuitry determines whether a difference between a previous position and the current position exceeds a predetermined hysteresis threshold. If the determined difference does not exceed the predetermined hysteresis threshold, the control circuitry masks the current position of the input object on the capacitive touch sense device.

Claims

1. A system comprising:

a radial slider coupled to capacitive touch sense circuitry that is configured to output an indication of a position of an input object relative to a surface of the radial slider; and

control circuitry comprising a first position register, a second position register and a scrolling hysteresis module, the scrolling hysteresis module to;

receive a first signal from the capacitive touch sense circuitry, the first signal indicating a previous radial position of the input object on the surface of the radial slider;

mask the previous radial position from an output of the control circuitry;

store the previous radial position in the first position register;

receive a second signal from the capacitive touch sense circuitry, the second signal indicating a current radial position of the input object on the surface of the radial slider;

store the current radial position in the second position register;

determine a difference between the current radial position stored in the second position register and the previous radial position stored in the first position register;

compare the determined difference to a hysteresis value, wherein the hysteresis value is a threshold representing a specified amount of angle for outputting or masking the current radial position;

mask the current radial position from the output of the control circuitry when the determined difference is less than the hysteresis value; and

output the current radial position from the output of the control circuitry when the determined difference is not less than the hysteresis value.

2. The system of claim 1 further comprising a button located below the surface of the radial slider, the button configured to change positions if the input object is pressed against the surface of the radial slider using a force that exceeds a force threshold, and wherein the control circuitry is further operable to:

receive an indication that the input object pressed against the surface of the radial slider using a force that exceeds the force threshold; and

output the press indication independently of whether the current radial position is masked.

3. The system of claim 1 wherein the hysteresis value is programmable.

4. An apparatus comprising control circuitry, wherein the control circuit comprising a first position register, a second position register and a scrolling hysteresis module, the control circuitry operable to:

receive a first indication of a previous radial position of an input object on a radial slider of a capacitive touch sense device;

store the previous radial position in a first position register;

mask the previous radial position from an output of the control circuitry;

receive a second indication of a current radial position of the input object on the radial slider of the capacitive touch sense device;

store the current radial position in a second position register;

determine a difference between the current radial position stored in the first position register and the previous radial position stored in the second position register;

compare the determined difference to a threshold value, the threshold value representing a specified amount of angle for outputting or masking the current radial position; and

mask an output the current radial position according to the comparison, when the determined difference is less than the threshold value; and

output the current radial position when the determined difference is not less than the threshold value.

5. The apparatus of claim 4 wherein the control circuitry is further operable to:

output indications of input object presses without filtering; and

filter indications of input object touches according to the comparison.

6. The apparatus of claim 4 wherein the control circuitry is further operable to:

identify a first threshold position and a second threshold position, the threshold positions corresponding to the previous radial position;

compare the threshold positions to determine if said positions are adjacent to a predefined wrap-around position on the radial slider; and

if the threshold positions are not adjacent to the predefined wrap-around position, mask the current radial position if the current radial position is between the threshold positions.

7. The apparatus of claim 6 wherein the control circuitry is further operable to:

if the threshold positions are adjacent to the predefined wrap-around position, mask the current radial position if the current radial position is not between the threshold positions.

8. The apparatus of claim 6, wherein the control circuitry is further operable to:

determine whether the threshold positions are adjacent to a predefined wrap-around position on the radial slider according to whether the first threshold position is greater than the second threshold.

9. The apparatus of claim 4 wherein the threshold value is selected according to a user input.

10. The apparatus of claim 4 wherein the radial slider is mapped to three hundred and sixty positions.

11. The apparatus of claim 4 wherein the control circuitry is further operable to:

determine whether the previous radial position is less than the threshold value;

if the previous radial position is not less than the threshold value, determine a first threshold position by subtracting the threshold value from the previous radial position; and

if the previous radial position is less than the threshold value, determine the first threshold position by first subtracting the previous radial position from the threshold value, and then subtracting the difference from the number of radial positions mapped to the radial slider.

12. The apparatus of claim 11 wherein the control circuitry is further operable to:

determine whether the sum of the previous radial position and the number of radial positions mapped to the radial slider is greater than the threshold value;

if the sum is not greater than the threshold value, determine the second threshold position by adding the threshold value to the previous radial position; and

if the sum is greater than the threshold value, determine the second threshold position by subtracting the number of radial positions from the sum of the previous radial position and the threshold value.

13. The apparatus of claim 4, wherein the control circuitry is further operable to:

calculate a rate that the input object has moved across the radial slider by dividing the determined distance by an amount of time;

compare the calculated rate to a threshold rate; and

output the current radial position according to both of the comparisons.

14. A method comprising:

detecting a first radial position of an input object on a radial slider of a capacitive touch sense device;

storing the first radial position;

masking, by a control circuitry, wherein the control circuit comprising a first radial position register, a second radial position register and a scrolling hysteresis module, the first radial position from being output from the control circuitry;

detecting a second radial position of the input object on the radial slider of the capacitive touch sense device;

determining a difference between the detected second radial position and the previously detected first radial position;

comparing the determined difference to a hysteresis value, the hysteresis value representing a specified amount of angle for outputting or masking the detected second radial position; and

filtering the detected second radial position based at least in part on the determined difference being less than the hysteresis value.

15. The method of claim 14 further comprising:

receiving an indication that the input object pressed against the radial slider using an amount of force exceeding a force threshold; and

outputting the press indication independently of whether the detected radial position is filtered.

16. The method of claim 14 further comprising:

determining whether the previously detected radial position is less than a threshold value;

if the previously detected radial position is not less than the threshold value, determining a first threshold position by subtracting the threshold value from the previously determining radial position; and

if the previously detected radial position is less than the threshold value, determining the first threshold position by subtracting the previously detected radial position from the threshold value, and then subtracting the difference from the number of radial positions mapped to the radial slider.

17. The method of claim 16 wherein the control circuitry is further operable to:

determining whether the sum of the previously detected radial position and the number of radial positions mapped to the radial slider is greater than the threshold value;

if the sum is not greater than the threshold value, determining the second threshold position by adding the threshold value to the previously detected radial position; and

if the sum is greater than the threshold value, determining the second threshold position by subtracting the number of radial positions from the sum of the previously detected radial position and the threshold value.

18. The method of claim 17 further comprising:

comparing the threshold positions to determine if said positions are adjacent to a predefined wrap-around position on the radial slider;

if the threshold positions are not adjacent to the predefined wrap-around position, masking the current radial position if the current radial position is between the threshold positions.

19. The method of claim 18 further comprising:

if the threshold positions are adjacent to the predefined wrap-around position, masking the current radial position if the current radial position is not between the threshold positions.

20. The method of claim 14 wherein the detected radial position is filtered according to a movement rate threshold.