Storing baseline information in EEPROM

• US 8,736,577 B2
• Filed: 12/07/2012
• Issued: 05/27/2014
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Land, Brian Richards, Westerman, Wayne Carl, Hotelling, Steve Porter
• Primary Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US13/708,675
• Publication Number:
  US 20130093710A1
• Time in Patent Office: 536 Days
• Field of Search: 345173-178, 178 1801- 1806
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Pre-stored no-touch or no-hover (no-event) sensor output values can initially be used when a sensor panel subsystem is first booted up to establish an initial baseline of sensor output values unaffected by fingers or other objects touching or hovering over the sensor panel during boot-up. This initial baseline can then be normalized so that each sensor generates the same output value for a given amount of touch or hover, providing a uniform response across the sensor panel and enabling subsequent touch or hover events to be more easily detected. After the initial normalization process is complete, the pre-stored baseline can be discarded in favor of a newly captured no-event baseline that may be more accurate than the pre-stored baseline due to temperature or other variations.

Claims

1. A method for determining an adjustment interval for a touch sensor panel, comprising:

performing a scan of the touch sensor panel to obtain sensor output values;

identifying non-touch sensor output values indicative of an absence of a touch or hover event;

computing an average of the non-touch sensor output values; and

choosing a time interval for adjusting subsequent sensor output values as a function of the computed average.

2. The method of claim 1, wherein the adjusting of subsequent sensor output values includes baseline drift compensation.

3. The method of claim 1, further comprising choosing the adjustment interval to be a first time interval if the computed average is negative.

4. The method of claim 3, further comprising:

if the computed average took longer than a second time interval to change from negative to positive, setting the adjustment interval to the second time interval, the second time interval being longer than the first time interval; and

if the background average is neutral or took less than the second time interval to change from negative to positive, then

if a hover event was detected in a previous touch sensor panel scan, setting the adjustment interval to a fourth time interval longer than the second time interval,

if a touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a fifth time interval longer than the fourth time interval, and

if neither a hover nor touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a third time interval, the third time interval between the second and fourth time intervals in duration.

5. The method of claim 4, further comprising determining that the computed average is positive when the computed average is about two standard deviations above neutral.

6. The method of claim 3, further comprising determining that the computed average is negative when the computed average is about one standard deviation below neutral.

7. The method of claim 1, further comprising:

setting the adjustment interval to a first time interval if the computed average indicates that the touch sensor panel is warming up.

8. The method of claim 7, further comprising:

setting the adjustment interval to a second time interval longer than the first time interval if the computed average indicates that the touch sensor panel is cooling down; and

if the computed average is neutral or took less than the second time interval to change from negative to positive, then

setting the adjustment interval to a fourth time interval longer than the second time interval if a previous touch sensor panel scan indicates an occurrence of a hover event,

setting the adjustment interval to a fifth time interval longer than the fourth time interval if the previous touch sensor panel scan indicates an occurrence of a touch event, and

if neither a hover nor a touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a third time interval, the third time interval between the second and fourth time intervals in duration.

9. An apparatus for determining an adjustment interval for a touch sensor panel, comprising:

a processor capable of

performing a scan of the touch sensor panel to obtain sensor output values;

identifying non-touch sensor output values indicative of an absence of a touch or hover event;

computing an average of the non-touch sensor output values; and

choosing a time interval for adjusting subsequent sensor output values as a function of the computed average.

10. The apparatus of claim 9, wherein the adjusting of subsequent sensor output values includes baseline drift compensation.

11. The apparatus of claim 9, wherein the processor is further capable of choosing the adjustment interval to be a first time interval if the computed average is negative.

12. The apparatus of claim 11, the processor further capable of:

if the computed average took longer than a second time interval to change from negative to positive, setting the adjustment interval to the second time interval, the second time interval being longer than the first time interval; and

if the background average is neutral or took less than the second time interval to change from negative to positive, then

if a hover event was detected in a previous touch sensor panel scan, setting the adjustment interval to a fourth time interval longer than the second time interval,

if a touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a fifth time interval longer than the fourth time interval, and

if neither a hover nor touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a third time interval, the third time interval between the second and fourth time intervals in duration.

13. The apparatus of claim 12, the processor further capable of determining that the computed average is positive when the computed average is about two standard deviations above neutral.

14. The apparatus of claim 11, the processor further capable of determining that the computed average is negative when the computed average is about one standard deviation below neutral.

15. The apparatus of claim 9, the processor further capable of:

setting the adjustment interval to a first time interval if the computed average indicates that the touch sensor panel is warming up.

16. The apparatus of claim 15, the processor further capable of:

setting the adjustment interval to a second time interval longer than the first time interval if the computed average indicates that the touch sensor panel is cooling down; and

if the computed average is neutral or took less than the second time interval to change from negative to positive, then

setting the adjustment interval to a fourth time interval longer than the second time interval if a previous touch sensor panel scan indicates an occurrence of a hover event,

setting the adjustment interval to a fifth time interval longer than the fourth time interval if the previous touch sensor panel scan indicates an occurrence of a touch event, and

if neither a hover nor a touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a third time interval, the third time interval between the second and fourth time intervals in duration.

17. The apparatus of claim 9, the apparatus coupled to the touch sensor panel.

18. The apparatus of claim 9, the apparatus incorporated into a mobile telephone.

19. The apparatus of claim 9, the apparatus incorporated into a digital audio player.

20. A non-transitory computer-readable storage medium comprising program code for determining an adjustment interval for a touch sensor panel, the program code for causing performance of a method comprising:

performing a scan of the touch sensor panel to obtain sensor output values;

identifying non-touch sensor output values indicative of an absence of a touch or hover event;

computing an average of the non-touch sensor output values; and

choosing a time interval for adjusting subsequent sensor output values as a function of the computed average.

21. The non-transitory computer-readable storage medium of claim 20, wherein the adjusting of subsequent sensor output values includes baseline drift compensation.

22. The non-transitory computer-readable storage medium of claim 20, the method further comprising choosing the adjustment interval to be a first time interval if the computed average is negative.

23. The non-transitory computer-readable storage medium of claim 22, the method further comprising:

if the computed average took longer than a second time interval to change from negative to positive, setting the adjustment interval to the second time interval, the second time interval being longer than the first time interval; and

if the background average is neutral or took less than the second time interval to change from negative to positive, then

if a hover event was detected in a previous touch sensor panel scan, setting the adjustment interval to a fourth time interval longer than the second time interval,

if a touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a fifth time interval longer than the fourth time interval, and

if neither a hover nor touch event was detected in the previous touch sensor panel scan, setting the adjustment interval to a third time interval, the third time interval between the second and fourth time intervals in duration.

24. The non-transitory computer-readable storage medium of claim 23, the method further comprising determining that the computed average is positive when the computed average is about two standard deviations above neutral.

25. The non-transitory computer-readable storage medium of claim 22, the method further comprising determining that the computed average is negative when the computed average is about one standard deviation below neutral.