Methods and apparatus for performing capacitive touch sensing and proximity detection

• US 20110120784A1
• Filed: 11/21/2009
• Published: 05/26/2011
• Est. Priority Date: 11/21/2009
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Mejia, Simon, Teegarden, Craig R., Osoinach, Bryce T.
• Granted Patent: US 8,558,802 B2
• Time in Patent Office: Days
• US Class Current: 178/18.06
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

Embodiments include methods and apparatus for performing capacitive touch sensing and proximity detection. Electrode selection circuitry establishes a first connection with an individual electrode of a plurality of individual electrodes in order to receive one or more first signals indicating a state of the individual electrode, and establishes second connections with a proximity electrode that comprises multiple ones of the plurality of individual electrodes in order to receive one or more second signals indicating a state of the proximity electrode. A processing system performs a first analysis on the first signals to determine whether to perform a first updating process for an individual electrode baseline value, and performs a second analysis on the second signals to determine whether to perform a second updating process for a proximity electrode baseline value. In an embodiment, the first analysis and the second analysis are different from each other.

Claims

1. A method for performing capacitive touch sensing and proximity detection, the method comprising the steps of:

establishing a first connection with an individual electrode of a plurality of individual electrodes in order to receive one or more first signals indicating a state of the individual electrode;

performing a first analysis of the one or more first signals to determine whether to perform a first updating process for an individual electrode baseline value;

establishing second connections with a proximity electrode that comprises multiple ones of the plurality of individual electrodes in order to receive one or more second signals indicating a state of the proximity electrode; and

performing a second analysis on the one or more second signals to determine whether to perform a second updating process for a proximity electrode baseline value, wherein the first analysis and the second analysis are different from each other.

2. The method of claim 1, wherein the first analysis includes a first filtering process, and the second analysis includes a second filtering process, the method further comprising:

prior to performing the first analysis, storing first filtering parameters that constrain the first filtering process; and

prior to performing the second analysis, storing second filtering parameters that constrain the second filtering process, wherein the first filtering parameters are different from the second filtering parameters.

3. The method of claim 2, wherein:

storing the first filtering parameters comprises storing a first filter delay limit value that specifies a number of the one or more first signals that will be used to determine a first comparison value for use in the first filtering process; and

storing the second filtering parameters comprises storing a second filter delay limit value that specifies a number of the one or more second signals that will be used to determine a second comparison value for use in the second filtering process, wherein the first filter delay limit value and the second filter delay limit value are different from each other.

4. The method of claim 2, wherein:

storing the first filtering parameters comprises storing a first maximum half delta value that specifies a largest difference between a first comparison value and the individual electrode baseline value that classifies the first comparison value as non-noise; and

storing the second filtering parameters comprises storing a second maximum half delta value that specifies a largest difference between a second comparison value and the proximity electrode baseline value that classifies the second comparison value as non-noise, wherein the first maximum half delta value and the second maximum half delta value are different from each other.

5. The method of claim 4, wherein:

storing the first filtering parameters comprises storing a first noise count limit value that specifies a number of consecutive first comparison values that have a difference with the individual electrode baseline value that is greater than the first maximum half delta value before a determination of non-noise drift is made; and

storing the second filtering parameters comprises storing a second noise count limit value that specifies a number of consecutive second comparison values that have a difference with the proximity electrode baseline value that is greater than the second maximum half delta value before a determination of non-noise drift is made, wherein the first noise count limit value and the second noise count limit value are different from each other.

6. The method of claim 2, wherein:

storing the first filtering parameters comprises storing a first noise half delta value that specifies a magnitude by which the individual electrode baseline value is to be adjusted when performing the first updating process; and

storing the second filtering parameters comprises storing a second noise half delta value that specifies a magnitude by which the proximity electrode baseline value is to be adjusted when performing the second updating process, wherein the first noise half delta value and the second noise half delta value are different from each other.

7. The method of claim 1, further comprising:

performing an individual electrode charging process by charging the individual electrode according to first charging parameters;

determining a first voltage value for the individual electrode, which results from the individual electrode charging process;

determining whether the first voltage value meets a first criterion;

when the state of the individual electrode is a no-touch state and when the first voltage value meets the first criterion, transitioning the state of the individual electrode to a touch state;

performing a proximity electrode charging process by charging the proximity electrode according to second charging parameters;

determining a second voltage value for the proximity electrode, which results from the proximity electrode charging process;

determining whether the second voltage value meets a second criterion; and

when the state of the proximity electrode is a non-proximal state and when the second voltage value meets the second criterion, transitioning the state of the proximity electrode to a proximal state.

8. The method of claim 7, further comprising:

determining whether the first voltage value meets a third criterion;

when the state of the individual electrode is a touch state and when the first voltage value meets the third criterion, transitioning the state of the individual electrode to a no-touch state;

determining whether the second voltage value meets a fourth criterion; and

when the state of the proximity electrode is a proximal state and when the second voltage value meets the fourth criterion, transitioning the state of the proximity electrode to a non-proximal state.

9. The method of claim 7, wherein:

the first charging parameters include a first charging current; and

the second charging parameters include a second charging current that is different from the first charging current.

10. The method of claim 7, wherein:

the first charging parameters include a first charging interval; and

the second charging parameters include a second charging interval that is different from the first charging interval.

11. The method of claim 1, wherein the multiple ones of the plurality of individual electrodes comprising the proximity electrode are in a close proximity to each other.

12. The method of claim 1, further comprising:

determining whether the proximity electrode is enabled or disabled; and

when the proximity electrode is disabled, bypassing the steps of establishing the second connections and performing the second analysis.

13. The method of claim 1, wherein the first analysis includes a first filtering process, and the second analysis includes a second filtering process, and wherein:

the first filtering process has a first frequency response; and

the second filtering process has a second frequency response that is different from the first frequency response.

14. A method for performing capacitive touch sensing and proximity detection, the method comprising the steps of:

storing first charging parameters and first analysis parameters associated with performing first charging and sensing processes for an individual electrode of a plurality of individual electrodes;

storing second charging parameters and second analysis parameters associated with performing second charging and sensing processes for a proximity electrode that comprises multiple ones of the plurality of individual electrodes, wherein the first charging and sensing operations are configured differently from the second charging and sensing operations;

establishing a first connection with the individual electrode;

charging the individual electrode in accordance with the first charging parameters;

receiving a first signal indicating a state of the individual electrode;

determining, based on the first signal, whether to perform a first updating process for an individual electrode baseline value by performing a first analysis that is constrained by the first analysis parameters;

establishing second connections with the proximity electrode;

charging the proximity electrode in accordance with the second charging parameters;

receiving a second signal indicating a state of the proximity electrode; and

determining, based on the second signal, whether to perform a second updating process for a proximity electrode baseline value by performing a second analysis that is constrained by the second analysis parameters.

15. The method of claim 14, wherein the first charging parameters are different from the second charging parameters.

16. The method of claim 14, wherein the first analysis parameters are different from the second analysis parameters.

17. The method of claim 14, further comprising:

determining whether the proximity electrode is enabled or disabled; and

when the proximity electrode is disabled, bypassing the steps of establishing the second connections, charging the proximity electrode, receiving the second signal, and determining whether to perform the second updating process.

18. A capacitive touch and proximity sensor system comprising:

electrode selection circuitry configured to establish a first connection with an individual electrode of a plurality of individual electrodes in order to receive one or more first signals indicating a state of the individual electrode, and to establish second connections with a proximity electrode that comprises multiple ones of the plurality of individual electrodes in order to receive one or more second signals indicating a state of the proximity electrode; and

a processing system, operatively coupled with the electrode selection circuitry, and configured to perform a first analysis on the one or more first signals to determine whether to perform a first updating process for an individual electrode baseline value, and to perform a second analysis on the one or more second signals to determine whether to perform a second updating process for a proximity electrode baseline value, wherein the first analysis and the second analysis are different from each other.

19. The capacitive touch and proximity sensor system of claim 18, wherein the electrode selection circuitry comprises:

a multiplexer configured to establish the first connection in response to a first control signal from the processing system, and to establish the second connections in response to a second control signal from the processing system.

20. The capacitive touch and proximity sensor system of claim 18, further comprising:

a current source, operatively coupled to the processing system and to the electrode selection circuitry, and configured to supply a first charging current to the individual electrode and to supply a second charging current to the proximity electrode, wherein the first charging current and the second charging current are different from each other.