ELECTRONIC DEVICE AND METHOD FOR DETERMINING A TOUCH INPUT APPLIED TO A CAPACITIVE TOUCH PANEL SYSTEM INCORPORATED THEREIN

• US 20110157069A1
• Filed: 12/31/2009
• Published: 06/30/2011
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Alberth, William P. JR., Zhuang, Zhiming, Foo, Ken K.
• Granted Patent: US 8,542,202 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

An electronic device is operable to determine a touch input applied to a capacitive touch panel system thereof so as to account for time-varying noise affecting the touch panel system. The electronic device includes the touch panel system, an analog-to-digital conversion (ADC) unit, and a processing unit. The processing unit is operable to: receive digital signal values from the ADC unit representing capacitances detected by sensing points of the touch panel system; adjust at least one of the digital signal values based at least on a time-varying noise to produce at least one noise-adjusted value; and determine the touch input based on the at least one noise-adjusted value. In one embodiment, the electronic device determines the time-varying noise prior to adjusting the digital signal values. In another embodiment, the time-varying noise is produced by a display panel of a touchscreen display that also includes the touch panel system.

Claims

1. A method for an electronic device to determine a touch input applied to a capacitive touch panel system of the electronic device, the capacitive touch panel system including a plurality of sensing points, the method comprising:

detecting capacitance at each of the plurality of sensing points to produce a plurality of sensed values;

adjusting at least one sensed value of the plurality of sensed values based at least on a time-varying noise to produce at least one noise-adjusted value, the time-varying noise affecting the capacitive touch panel system; and

determining the touch input based on the at least one noise-adjusted value.

2. The method of claim 1, further comprising:

determining the time-varying noise affecting the capacitive touch panel system prior to adjusting the at least one sensed value.

3. The method of claim 2, wherein determining the time-varying noise comprises:

detecting time-varying noise at one or more input-protected sensing points of the plurality of sensing points, wherein the one or more input-protected sensing points are protected from application of the touch input.

4. The method of claim 2, wherein determining the time-varying noise further comprises:

adjusting at least one sensed value of the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain to produce at least one adjusted value; and

determining a time-varying noise value corresponding to the time-varying noise based on the at least one adjusted value.

5. The method of claim 4, wherein adjusting at least one sensed value of the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain comprises:

adjusting the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain to produce a plurality of adjusted values;

determining an average of the plurality of adjusted value to produce an average value;

comparing each adjusted value of the plurality of adjusted values to the average value to produce a plurality of comparison results;

determining a subset of the plurality of adjusted values based on the plurality of comparison results; and

determining an average of the subset of adjusted values to produce the time-varying noise value.

6. The method of claim 5, wherein adjusting at least one sensed value of the plurality of sensed values based at least on a time-varying noise comprises:

filtering the time-varying noise value from each of the plurality of sensed values to produce the at least one noise-adjusted value.

7. The method of claim 4, wherein adjusting at least one sensed value of the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain comprises:

normalizing the at least one sensed value to account for static, spatial-varying noise and static, spatial-varying gain to produce the at least one adjusted value.

8. A method for an electronic device to determine a touch input applied to a capacitive touch panel system of the electronic device so as to account for time-varying noise affecting the touch panel system, the touch panel system including a plurality of sensing points, the method comprising:

detecting a capacitance at each sensing point of the plurality of sensing points to produce a plurality of sensed values;

normalizing each of the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain to produce a plurality of normalized values;

determining an average of the plurality of normalized values to produce an average value;

comparing each of the plurality of normalized values to the average value to produce a plurality of comparison results;

determining a subset of the plurality of normalized values based on the plurality of comparison results;

determining an average of the subset of normalized values to produce a time-varying, common mode noise value; and

determining the touch input based on filtering of the time-varying, common mode noise value from each of the plurality of sensed values.

9. The method of claim 8, wherein the time-varying noise affecting the touch panel system results at least in part from operation of at least one electronic noise source, the method further comprising:

determining, based on the plurality of comparison results, whether the touch input is present;

responsive to determining that the touch input is present, slowing operation of the at least one electronic noise source on a temporary basis; and

while operation of the at least one electronic noise source is slowed and prior to determining the subset of normalized values, repeating the steps of detecting a capacitance at each sensing point of the plurality of sensing points, normalizing each of the plurality of sensed values, determining the average value, and comparing each of the plurality of normalized values to the average value.

10. The method of claim 9, wherein the at least one electronic noise source includes a display panel of the electronic device and wherein slowing operation of the at least one electronic noise source on a temporary basis comprises temporarily freezing operation of at least part of the display panel.

11. The method of claim 8, wherein determining whether the touch input is present comprises:

determining whether at least one of the plurality of normalized values is greater than the average value by a predetermined threshold.

12. The method of claim 8, wherein determining whether the touch input is present comprises:

determining whether at least one of the plurality of normalized values is less than the average value by a predetermined threshold.

13. The method of claim 8, wherein the plurality of sensing points includes a plurality of excitation nodes and a plurality of output nodes configured in a grid arrangement and wherein detecting a capacitance at each sensing point of the plurality of sensing points comprises:

applying a plurality of excitation signals to the plurality of excitation nodes;

scanning the plurality of output nodes to detect a corresponding plurality of output signals responsive to the plurality of excitation signals; and

determining the capacitance at each sensing point based on a corresponding output signal of the plurality of output signals.

14. The method of claim 13, wherein scanning the plurality of output nodes comprises:

scanning the plurality of output nodes in a predetermined order to detect the corresponding plurality of output signals responsive to the plurality of excitation signals.

15. The method of claim 13, wherein scanning the plurality of output nodes comprises:

scanning the plurality of output nodes in a random order to detect the corresponding plurality of output signals responsive to the plurality of excitation signals.

16. The method of claim 13, wherein scanning the plurality of output nodes comprises:

scanning the plurality of output nodes substantially simultaneously to detect the corresponding plurality of output signals responsive to the plurality of excitation signals.

17. The method of claim 8, wherein the capacitance detected at a particular time and at a particular sensing point of the plurality of sensing points is defined by the following equation:

R(n,t)=G(n)*S(n·

t)+G(n)*D(t)+B(n),

where

n is a location of the particular sensing point in the touch panel system;

t is the particular time;

R(n,t) is a sensed value corresponding to the capacitance detected at the particular sensing point at the particular time;

G(n) is static, spatial-varying gain at the location of the particular sensing point;

S(n,t) represents a touch input signal at the location of the particular sensing point at the particular time;

D(t) is a time-varying, common mode noise value at the particular time; and

B(n) is static, spatial-varying noise at the location of the particular sensing point.

18. The method of claim 17, wherein normalizing each of the plurality of sensed values comprises:

subtracting corresponding static, spatial-varying noise from each of the plurality of sensed values to produce a plurality of differences, wherein each of the plurality of differences is represented by R(n,t)−

B(n) for the particular time and the particular sensing point; and

dividing each of the plurality of differences by a corresponding static, spatial varying gain to produce the plurality of normalized values, wherein each of the plurality of normalized values is represented by R′

(n,t)=[R(n,t)−

B(n)]/G(n) for the particular time and the particular sensing point.

19. The method of claim 18, wherein the average of the plurality of normalized values is determined by the following equation:

AvgR′

(n,t)=Σ

R′

(n,t)/N=Σ

S(n,t)/N+Σ

D(t)/N,

where

AvgR′

(n,t) is the average value; and

N is a total quantity of the plurality of sensing points; and

wherein R′

(n,t) is determined and summed for all of the plurality of sensing points.

20. The method of claim 19, wherein the average of the subset of normalized values is determined according to the following equation:

D(t)=Σ

R″

(n,t)/N′

,

where

D(t) is the time-varying, common mode noise value; and

N′

is a quantity of the subset of normalized values and is less than or equal to N; and

wherein R″

(n,t)=[R(n,t)−

B(n)]/G(n) and is determined only for sensing points of the plurality of sensing points for which a touch input is absent based on the plurality of comparison results.

21. An electronic device comprising:

a capacitive touch panel system that includes a plurality of sensing points which are operable to receive a touch input from a user of the electronic device;

an analog-to-digital conversion (ADC) unit operably coupled to the plurality of sensing points for converting analog output signals from the plurality of sensing points to digital signal values; and

a processing unit operably coupled to the ADC unit and operable in accordance with a set of operating instructions to;

receive digital signal values from the ADC unit representing capacitances detected by the plurality of sensing points to produce a plurality of sensed values;

adjust at least one sensed value of the plurality of sensed values based at least on a time-varying noise to produce at least one noise-adjusted value, the time-varying noise affecting the capacitive touch panel system; and

determine the touch input based on the at least one noise-adjusted value.

22. The electronic device of claim 21, wherein the processing unit is further operable in accordance with the set of operating instructions to:

determine the time-varying noise affecting the capacitive touch panel system prior to adjusting the at least one sensed value.

23. The electronic device of claim 22, wherein the processing unit is further operable in accordance with the set of operating instructions to determine the time-varying noise affecting the capacitive touch panel system by:

normalizing each of the plurality of sensed values to account for static, spatial-varying noise and static, spatial-varying gain to produce a plurality of normalized values;

determining an average of the plurality of normalized values to produce an average value;

comparing each of the plurality of normalized values to the average value to produce a plurality of comparison results;

determining a subset of the plurality of normalized values based on the plurality of comparison results; and

determining an average of the subset of normalized values to produce a time-varying noise value corresponding to the time-varying noise.

24. The electronic device of claim 23, wherein the processing unit is further operable in accordance with the set of operating instructions to adjust at least one sensed value of the plurality of sensed values based at least on the time-varying noise by:

filtering the time-varying noise value from each of the plurality of sensed values to produce the at least one noise-adjusted value.

25. The electronic device of claim 23, further comprising:

at least one electronic noise source that is controllable by the processing unit, wherein the time-varying noise affecting the capacitive touch panel system results at least in part from operation of the at least one electronic noise source; and

wherein the processing unit is further operable in accordance with the set of operating instructions to;

determine, based on the plurality of comparison results, whether the touch input is present;

responsive to a determination that the touch input is present, slow operation of the at least one electronic noise source on a temporary basis; and

while operation of the at least one electronic noise source is slowed and prior to determining the subset of normalized values, repeat operations of detecting a capacitance at each sensing point of the plurality of sensing points, normalizing each of the plurality of sensed values, determining the average value, and comparing each of the plurality of normalized values to the average value.

26. The electronic device of claim 25, wherein the at least one electronic noise source includes a display panel, wherein the capacitive touch panel system and the display panel form a touchscreen display, and wherein the processing unit is operable to slow operation of the at least one electronic noise source by temporarily freezing operation of at least part of the display panel.