Negative touch recovery for mutual capacitance scanning systems

• US 9,285,932 B1
• Filed: 03/26/2012
• Issued: 03/15/2016
• Est. Priority Date: 07/28/2011
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Parade Technologies, Ltd.
• Inventors: Wavomba, Dennis
• Primary Examiner(s): Patel, Kumar
• Assistant Examiner(s): Ahn, Sejoon
• Application Number:
  US13/429,878
• Time in Patent Office: 1,450 Days
• Field of Search: 345173-175
• US Class Current: 1/1
• 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 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A device stores running baseline measurements and initial baseline measurements for a plurality of touch sensors. The device repeatedly takes measurements from the touch sensors during device operation, and counts a number of positive transitions of the measurements, and counts a number of negative transitions of the measurements, the transitions relative to the stored initial baseline measurements. The device re-initializes the stored initial baseline measurements if and only if the count of negative transitions differs from the count of positive transitions by a predetermined amount (a “negative touch state”).

Claims

1. A mobile communication device, comprising:

a touch-sensitive surface having a circuit configured for;

storing running baseline capacitance measurements and initial baseline capacitance measurements for a plurality of touch sensors of the touch-sensitive surface;

repeatedly taking capacitance measurements from the touch sensors during device operation, counting a number of positive transitions of the measurements, and counting a number of negative transitions of the measurements, wherein each positive transition includes capacitance measurements exceeding the stored initial baseline measurements by a predetermined first threshold amount, each negative transition includes capacitance measurements falling below the stored initial baseline measurements by a predetermined second threshold amount, and the predetermined first and second threshold amounts are specified independently;

determining that the count of negative transitions differs from the count of positive transitions by a predetermined amount; and

in response to determining that the count of negative transitions differs from the count of positive transitions by the predetermined amount, re-initializing the stored initial baseline capacitance measurements.

2. The mobile device of claim 1, wherein the circuit is further configured for:

continually altering the stored running baseline capacitance measurements during device operation, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

3. The mobile device of claim 1,

wherein the circuit is further configured for re-initializing the stored initial baseline capacitance measurements if and only if the count of negative transitions exceeds the count of positive transitions by a threshold amount.

4. The mobile device of claim 2,

wherein the circuit is further configured for continually altering the stored running baseline capacitance measurements during device operation according to changing environmental factors, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

5. The device of claim 4, wherein the circuit is further configured for determining

a touch or gesture by comparing current sensor measurements with the running baseline capacitance measurements, while determining if a negative touch state is present using the stored initial baseline capacitance measurements.

6. The device of claim 1,

wherein the circuit is further configured for continually re-initializing the stored initial baseline capacitance measurements until a negative touch state is cleared.

7. A device comprising a touch-sensitive surface having a circuit configured for:

storing running baseline capacitance measurements and initial baseline capacitance measurements for a plurality of touch sensors;

repeatedly taking capacitance measurements from the touch sensors during device operation, counting a number of positive transitions of the measurements, and counting a number of negative transitions of the measurements, wherein each positive transition includes capacitance measurements exceeding the stored initial baseline measurements by a predetermined first threshold amount, each negative transition includes capacitance measurements falling below the stored initial baseline capacitance measurements by a predetermined second threshold amount, and the predetermined first and second threshold amounts are specified independently; and

detecting a negative touch state in which the count of negative transitions differs from the count of positive transitions by a predetermined amount; and

in response to detecting the negative touch state, re-initializing the stored initial baseline capacitance measurements.

8. The device of claim 7, wherein the circuit is further configured for

continually altering the stored running baseline capacitance measurements during device operation, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

9. The device of claim 7,

wherein the circuit is further configured for re-initializing the stored initial baseline capacitance measurements if and only if the count of negative transitions exceeds the count of positive transitions by a threshold amount.

10. The device of claim 8,

wherein the circuit is further configured for continually altering the stored running baseline capacitance measurements during device operation according to changing environmental factors, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

11. The device of claim 10, wherein the circuit is further configured for

determining a touch or gesture by comparing current sensor measurements with the running baseline capacitance measurements, while determining if a negative touch state is present using the stored initial baseline capacitance measurements.

12. The device of claim 7,

wherein the circuit is further configured for continually re-initializing the stored initial baseline capacitance measurements until a negative touch state is cleared.

13. A method performed at a touch-sensitive device with a plurality of touch sensors, comprising:

upon transitioning the touch-sensitive device from a sleep state to an active state, scanning the plurality of touch sensors to establish baseline capacitance measurements;

after transitioning the touch-sensitive device from the sleep state to the active state;

storing running baseline capacitance measurements and initial baseline capacitance measurements for the plurality of touch sensors;

repeatedly taking capacitance measurements from the touch sensors during operation of the touch-sensitive device, counting a number of positive transitions of the capacitance measurements, and counting a number of negative transitions of the capacitance measurements, wherein each positive transition includes capacitance measurements exceeding the stored initial baseline capacitance measurements by a predetermined first threshold amount, each negative transition includes capacitance measurements falling below the stored initial baseline capacitance measurements by a predetermined second threshold amount, and the first and second threshold amounts are asymmetrical;

determining that the count of negative transitions differs from the count of positive transitions by a predetermined amount; and

in response to determining that the count of negative transitions differs from the count of positive transitions by a predetermined amount, re-initializing the stored initial baseline capacitance measurements.

14. The method of claim 13, further comprising:

continually altering the stored running baseline capacitance measurements during operation of the touch-sensitive device, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

15. The method of claim 13, further comprising:

re-initializing the stored initial baseline capacitance measurements if and only if the count of negative transitions exceeds the count of positive transitions by a threshold amount.

16. The method of claim 14, further comprising:

continually altering the stored running baseline capacitance measurements during operation of the touch-sensitive device according to changing environmental factors, while maintaining the stored initial baseline capacitance measurements unaltered until a negative touch state is determined.

17. The method of claim 16, further comprising:

determining a touch or gesture by comparing current sensor capacitance measurements with the running baseline capacitance measurements, while determining if a negative touch state is present using the stored initial baseline capacitance measurements.

18. The method of claim 13, wherein the predetermined first and second threshold amounts are set according to design environment, sensor type, and application.

19. The method of claim 13, wherein repeatedly taking measurements from the touch sensors during operation of the touch-sensitive device includes continually scanning for subsequent capacitance measurements after taking a first capacitance measurement.