Touch panel controller integrated with host processor for dynamic baseline image update

• US 9,921,668 B1
• Filed: 01/25/2013
• Issued: 03/20/2018
• Est. Priority Date: 01/25/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chadda, Trishabh, Shen, Guozhong, Pearson, Jon
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): Edwards, Mark
• Application Number:
  US13/749,829
• Time in Patent Office: 1,880 Days
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• 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 touch panel controller is disclosed herein. The controller includes output circuitry for driving a touch panel sensor and input circuitry for determining when an object performs a touch event over the touch panel sensor. The controller is configured to cause the output circuitry to generate drive signals having a different frequency characteristic when the controller determines noise present within the sensor is above a noise threshold. The controller communicates with a software device driver on a host processor to store signal baseline images for a range of frequencies during production test and power-up. The controller is configured to receive a signal baseline image from the host processor when the controller causes change to a different drive frequency. The controller is configured to cause change to the different drive frequency while the object is still performing the touch event over the touch panel sensor.

Claims

1. An apparatus comprising:

a touch panel controller configured to operatively couple to a touch panel sensor, the touch panel sensor including a plurality of drive electrodes and at least one sense electrode, a plurality of nodes being formed at intersections of the plurality of drive electrodes and the at least one sense electrode, the touch panel controller comprising;

output circuitry operatively coupled to the plurality of drive electrodes, the output circuitry capable of generating drive signals having a configurable frequency characteristic occurring within a range of frequencies to drive the touch panel sensor; and

input circuitry operatively coupled to the at least one sense electrode, the input circuitry capable of measuring capacitance formed at each intersection of the plurality of drive electrodes and of the at least one sense electrode,

wherein the apparatus is configured to;

obtain a plurality of signal baseline images during a power-up mode of the apparatus, the plurality of signal baseline images including a plurality of capacitance values measured at the intersections of the plurality of drive electrodes and the at least one sense electrode, each signal baseline image of the plurality of signal baseline images corresponding to a drive frequency;

store the plurality of signal baseline images in a storage device;

cause the output circuitry to generate drive signals at a first frequency;

determine when a first noise level of the touch panel is above a noise threshold while the output circuitry generates drive signals at the first frequency and, when the first noise level is above the noise threshold, determine noise levels at each of a plurality of drive frequencies;

select a second drive frequency that corresponds with a second noise level that is lower than the first noise level;

cause the output circuitry to generate drive signals at the second drive frequency; and

calculate a prediction of a signal baseline image corresponding with the second drive frequency, the prediction being based, at least in part, on a signal baseline image selected from the plurality of signal baseline images obtained and stored during the power-up mode of the apparatus.

2. The apparatus as recited in claim 1, further comprising a host processor, wherein the touch panel controller is capable of communicating with the host processor.

3. The apparatus as recited in claim 1, wherein the signal baseline image comprises a plurality of capacitive values measured at a selected drive frequency, each capacitive value corresponding to a node of the plurality of nodes.

4. The apparatus as recited in claim 1, wherein the output circuitry comprises a digital-to-analog converter coupled to a buffer the buffer coupled to at least one drive electrode of the plurality of drive electrodes.

5. The apparatus as recited in claim 1, wherein the input circuitry comprises a charge amplifier, the charge amplifier further comprising an operational amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal, the inverting input terminal coupled to at least one sense electrode;

and an integrating capacitor electrically coupled between the inverting input terminal and the output terminal.

16. The apparatus as recited in claim 1, wherein the apparatus is configured to use the prediction of the signal baseline image as a datum for detecting changes in capacitance caused by an object that is positioned in contact with or in proximity to the touch panel sensor.

17. The apparatus as recited in claim 1, wherein the apparatus is configured to calculate the prediction of the signal baseline image while one or more objects are positioned in contact with or in proximity to the touch panel sensor.

20. The apparatus as recited in claim 1, wherein the apparatus is configured to:

determine a composite baseline image based on a signal baseline image obtained during the power-up mode of the apparatus and a signal baseline image obtained during a previous time of touch panel calibration; and

calculate the prediction of the signal baseline image based, at least in part, on the composite baseline image.

6. A system comprising:

a touch panel sensor capable of detecting a change in capacitance associated with an object positioned over the touch panel sensor;

a touch panel controller operatively coupled to the touch panel sensor, the touch panel controller capable of;

obtaining a plurality of signal baseline images during a power-up mode of the system the plurality of signal baseline images including a plurality of capacitance values measured at intersections of a plurality of drive electrodes and at least one sense electrode of the touch panel sensor, each signal baseline image of the plurality of signal baseline images corresponding to a drive frequency;

storing the plurality of signal baseline images in a storage device;

causing the generation of at least one drive signal having a first frequency characteristic occurring within a range of drive frequencies to drive the touch panel sensor;

measuring noise present within the touch panel sensor; and

measuring a signal baseline image of the touch panel sensor within the range of drive frequencies;

a host processor operatively coupled to the touch panel controller, the host processor being capable of communicating with the touch panel controller; and

at least one storage device that is communicatively coupled to the host processor and capable of storing the signal baseline images

wherein the system is capable of;

determining when a first noise level of the touch panel is above a noise threshold while the output circuitry is generating drive signals at the first frequency characteristic and, when the first noise level is above the noise threshold, determining noise levels at each of a plurality of drive frequencies;

selecting a second drive frequency characteristic that corresponds with a second noise level that is lower than the first noise level;

calculating a prediction of a signal baseline image corresponding with the second drive frequency characteristic, the prediction being based, at least in part, on a signal baseline image selected from the plurality of signal baseline images obtained and stored during the power-up mode; and

causing the generation of at least one drive signal having the second drive frequency characteristic.

7. The system as recited in claim 6, wherein the baseline image comprises a plurality of capacitive values measured at a selected drive frequency occurring within the range of frequencies, each capacitive value corresponding to a capacitive node within the touch panel sensor.

8. The system as recited in claim 6, wherein touch panel controller includes output circuitry communicatively coupled to the touch panel sensor, the output circuitry capable of generating drive signals having frequency characteristics occurring within the range of frequencies.

9. The system as recited in claim 8, wherein the output circuitry comprises a digital-to-analog converter coupled to a buffer, the buffer coupled to at least one drive electrode of the plurality of drive electrodes.

10. The system as recited in claim 6, wherein the touch panel controller includes input circuitry communicatively coupled to the touch panel sensor, the input circuitry capable of determining when the object performs a touch event over the touch panel sensor.

11. The system as recited in claim 10, wherein the input circuitry comprises a charge amplifier, the charge amplifier further comprising an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal coupled to at least one sense electrode;

and an integrating capacitor electrically coupled between the inverting input terminal and the output terminal.

12. The system as recited in claim 6, wherein the host processor comprises an applications processor.

13. The system as recited in claim 6, wherein the system is controlled, at least in part, by a software module operating integrated to an operating system in the host processor.

18. The system as recited in claim 6, wherein the apparatus is configured to use the prediction of the signal baseline image as a datum for detecting changes in capacitance caused by an object that is positioned in contact with or in proximity to the touch panel sensor.

19. The system as recited in claim 6, wherein the apparatus configured to calculate the prediction of the signal baseline image while one or more objects are positioned in contact with or in proximity to the touch panel sensor.

14. A method comprising:

obtaining a plurality of signal baseline images during a power-up mode of a touch panel sensor, the plurality of signal baseline images including a plurality of capacitance values measured at the intersections of a plurality of drive electrodes and at least one sense electrode of the touch panel sensor, each signal baseline image of the plurality of signal baseline images corresponding to a drive frequency, each signal baseline image including capacitive values measured within the touch panel sensor at a corresponding drive frequency;

storing the plurality of signal baseline images in a storage device;

generating a drive signal having a first frequency characteristic to drive the touch panel sensor, the touch panel sensor including a plurality of drive electrodes and sense electrodes, a plurality of nodes formed at intersections of the plurality of drive electrodes and the plurality of sense electrodes, each node of the plurality of nodes having a corresponding capacitive value;

detecting noise having a noise level above a noise threshold value, the noise present within the touch panel sensor associated with the drive signal having the first frequency characteristic;

selecting a second frequency within the predefined frequency range having a lower noise level as compared to the noise level associated with the drive signal having the first frequency characteristic; and

calculating a prediction of a signal baseline image corresponding with the second drive frequency, the prediction being based, at least in part, on a signal baseline image selected from the plurality of signal baseline images obtained and stored during the power-up mode.

15. The method as recited in claim 14, wherein the calculating occurs during a time when one or more objects are in contact with or in proximity to a touch panel sensor.