Auto Scanning for Multiple Frequency Stimulation Multi-Touch Sensor Panels

• US 20090189867A1
• Filed: 01/30/2008
• Published: 07/30/2009
• Est. Priority Date: 01/30/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hotelling, Steve Porter, KRAH, Christoph Horst
• Granted Patent: US 10,969,917 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• 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

The use of multiple stimulation frequencies and phases is disclosed to detect touch events on a touch sensor panel in a low-power state. Simultaneously during every frame, a number of rows of the touch sensor panel can be driven with a positive phase of one or more stimulation signals, and the same number of different rows can be driven with the anti-phase of those same stimulation signals. Because the same number of rows are stimulated with the in-phase and anti-phase components of the one or more stimulation signals, the resulting charges injected into a given column cancel each other out. However, a touch event will create an imbalance, and a non-zero charge will be detected. The detection of the touch event can then trigger the system to wake up, activate a panel processor, and perform a full panel scan, where the location of the touch event can be identified.

Claims

1. A method for detecting whether a touch event has occurred on a touch sensor panel, comprising:

while maintaining a panel processor in an inactive state,

simultaneously driving a first group of rows of the touch sensor panel with one or more stimulation signals,

determining whether an output of one or more sense channels coupled to one or more columns of the touch sensor panel exceeds a predetermined threshold indicative of a touch event, and

if the output exceeds the threshold, triggering a subsequent capture of touch data for determining a location of the touch event.

2. The method of claim 1, further comprising:

driving the first group of rows driven with in-phase components of the one or more stimulation signals; and

simultaneously driving a second group of rows with anti-phase components of the one or more stimulation signals in a balanced manner so that in a no-touch condition, a net charge injected into each of one or more columns of the touch sensor panel is about zero.

3. The method of claim 2, the one or more first stimulation signals comprising two or more stimulation signals at different frequencies.

4. The method of claim 2, further comprising performing multiple scans of the touch sensor panel, each scan driving the rows of the touch sensor panel in a different balanced stimulation pattern.

5. The method of claim 2, further comprising balancing the one or more stimulation signals by driving a same number of rows with both the in-phase and anti-phase components of the one or more stimulation signals.

6. The method of claim 2, further comprising balancing the one or more stimulation signals by varying the number of rows driven by the in-phase and anti-phase components of the one or more stimulation signals and varying the amplitudes of the in-phase and anti-phase components of the one or more stimulation signals.

7. The method of claim 2, further comprising reducing a size of a feedback capacitor Cfb in the sense channel due to the balancing of the stimulation signals.

8. The method of claim 1, wherein the first group of rows include all of the rows in the touch sensor panel, and are simultaneously driven with a first stimulation signal of a same frequency and phase.

9. The method of claim 1, wherein one or more of the first stimulation signals are composite multi-frequency signals.

10. The method of claim 1, wherein one or more of the first stimulation signals are single-frequency signals.

11. The method of claim 1, further comprising setting the predetermined threshold to about a midpoint of a range of output values of the sense channels produced between the no-touch to a full-touch condition.

12. The method of claim 1, further comprising entering an advanced power management mode and applying a sequence of stimulation signals to the rows to over multiple frames and gathering data needed to determine a location of touch if it is determined that the output of one or more sense channels coupled to one or more columns of the touch sensor panel exceeds a predetermined threshold.

13. An apparatus for detecting whether a touch event has occurred on a touch sensor panel, comprising:

driver logic configured for providing stimulation signals to drive rows of the touch sensor panel;

a plurality of sense channels configured for detecting touch events on the touch sensor panel; and

auto-scan scan logic coupled to the driver logic and the plurality of sense channels, the auto-scan logic configured for

during an auto-scan cycle, and while maintaining a panel processor in an inactive state,

periodically triggering the driver logic to simultaneously drive a first group of rows of the touch sensor panel with one or more first stimulation signals,

determining whether an output of one or more sense channels exceeds a predetermined threshold indicative of a touch event, and

if the output exceeds the threshold, triggering a subsequent capture of touch data for determining a location of the touch event.

14. The apparatus of claim 13, the auto-scan logic further configured, during the auto-scan cycle, for:

periodically triggering the driver logic to simultaneously drive the first group of rows of the touch sensor panel with in-phase component of the one or more first stimulation signals, while simultaneously driving a second group of rows with anti-phase components of the one or more stimulation signals in a balanced manner so that in a no-touch condition, a net charge injected into each of one or more columns of the touch sensor panel is about zero.

15. The apparatus of claim 14, the one or more first stimulation signals comprising two or more stimulation signals at different frequencies.

16. The apparatus of claim 14, the auto-scan logic further configured for performing multiple scans of the touch sensor panel during the auto-scan cycle, each scan driving the rows of the touch sensor panel in a different balanced stimulation pattern.

17. The apparatus of claim 14, the auto-scan logic further configured for balancing the one or more first stimulation signals by driving a same number of rows with both the in-phase and anti-phase components of the one or more stimulation signals.

18. The apparatus of claim 14, the auto-scan logic further configured for balancing the one or more stimulation signals by varying the number of rows driven by the in-phase and anti-phase components of the one or more stimulation signals and varying the amplitudes of the in-phase and anti-phase components of the one or more stimulation signals.

19. The apparatus of claim 14, further comprising a feedback capacitor Cfb in each sense channel whose size is reduced as compared to the Cfb needed for unbalanced stimulation signals.

20. The apparatus of claim 13, wherein the first group of rows include all of the rows in the touch sensor panel, and are simultaneously driven with a first stimulation signal of a same frequency and phase.

21. The apparatus of claim 13, the driver logic further configured for providing composite multi-frequency first stimulation signals.

22. The apparatus of claim 13, the driver logic further configured for providing separate single-frequency first stimulation signals.

23. The apparatus of claim 13, the auto-scan logic further configured for detecting the touch event by determining whether an output value from one of the plurality of sense channel exceeds a threshold set at about a midpoint of a range of the output values of the sense channel produced between the no-touch to a full-touch condition.

24. The apparatus of claim 13, the auto-scan logic further configured for entering an advanced power management mode and applying a sequence of stimulation signals to the rows to over multiple frames and gathering data needed to determine a location of touch if it is determined that the output of one or more sense channels coupled to one or more columns of the touch sensor panel exceeds a predetermined threshold.

25. The apparatus of claim 24, wherein the advanced power management mode is entered while keeping the panel processing in the inactive state.

26. A computing system comprising the apparatus of claim 13.

27. A mobile telephone including an apparatus for detecting whether a touch event has occurred on a touch sensor panel, the apparatus comprising:

driver logic configured for providing stimulation signals to drive rows of the touch sensor panel;

a plurality of sense channels configured for detecting touch events on the touch sensor panel; and

auto-scan scan logic coupled to the driver logic and the plurality of sense channels, the auto-scan logic configured for

during an auto-scan cycle, and while maintaining a panel processor in an inactive state,

periodically triggering the driver logic to simultaneously drive a first group of rows of the touch sensor panel with one or more first stimulation signals,

determining whether an output of one or more sense channels exceeds a predetermined threshold indicative of a touch event, and

if the output exceeds the threshold, triggering a subsequent capture of touch data for determining a location of the touch event.

28. A digital audio player including an apparatus for detecting whether a touch event has occurred on a touch sensor panel, the digital audio player comprising:

driver logic configured for providing stimulation signals to drive rows of the touch sensor panel;

a plurality of sense channels configured for detecting touch events on the touch sensor panel; and

auto-scan scan logic coupled to the driver logic and the plurality of sense channels, the auto-scan logic configured for

during an auto-scan cycle, and while maintaining a panel processor in an inactive state,

periodically triggering the driver logic to simultaneously drive a first group of rows of the touch sensor panel with one or more first stimulation signals,

determining whether an output of one or more sense channels exceeds a predetermined threshold indicative of a touch event, and

if the output exceeds the threshold, triggering a subsequent capture of touch data for determining a location of the touch event.