Injected touch noise analysis

• US 8,874,396 B1
• Filed: 12/19/2013
• Issued: 10/28/2014
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Olson, Dana, Maharyta, Andriy, Kolokowsky, Steve
• Primary Examiner(s): TSAI, CAROL S W
• Application Number:
  US14/134,406
• Time in Patent Office: 313 Days
• Field of Search: 702/69, 345/173, 345/174
• US Class Current: 702/69
• CPC Class Codes: G06F 2203/04809 Textured surface identifying touch areas, e.g. overlay structure for a virtual keyboard
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G06F 3/04886 by partitioning the display area of the touch-screen or the surface of the digitising tablet into independently controllable areas, e.g. virtual keyboards or menus
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe

Abstract

A processing device configured to induce, during a listening scan of a sense array, an injected touch to produce similar data as would be present during a touch scan of the sense array with a conductive object at a known location on the sense array. The processing device is further configured to compute, using the data, an estimate of a noise metric based on the injected touch.

Claims

1. A method comprising:

performing a listening scan on a sense array to compute an estimate of a noise metric;

inducing, by a processing device during the listening scan of the sense array, an injected touch signal, the injected touch signal induced, at the processing device, independent from signals received from the sense array;

measuring, by the processing device, a signal, wherein the measured signal comprises the injected touch signal and a second signal originating from the sense array;

converting the measured signal into first data; and

computing the estimate of the noise metric in the measured signal based on the injected touch signal, wherein computing the estimate of the noise metric comprises comparing the first data and second data corresponding to the injected touch signal, the second data representing expected data that would result from a conductive object proximate to a known location on the sense array during a touch scan of the sense array.

2. The method of claim 1, wherein the known location comprises a cell of a plurality of cells of the sense array where a detected touch proximate the sense array occurs.

3. The method of claim 1, wherein the listening scan is performed independent of a transmitted stimulus signal.

4. The method of claim 1, wherein the performing of the listening scan comprises measuring the noise metric for a plurality of frequencies.

5. The method of claim 4, wherein the measuring is performed for the plurality of frequencies in parallel.

6. The method of claim 1, wherein the inducing comprises inducing the injected touch internal to a receiving circuit, and wherein the data of the injected touch is processed in an equivalent signal path to touch data from a touch proximate the sense array present during the touch scan of the sense array.

7. The method of claim 6, wherein a capacitance-sensing circuit comprises the receiving circuit.

8. The method of claim 1, further comprising

selecting a stimulus signal from a plurality of stimulus signals for the touch scan, wherein the touch scan measures the touch proximate the sense array, and wherein the selection of the stimulus signal is based on the noise metric, wherein the noise metric is indicative of noise characteristics of noise on the sense array.

9. The method of claim 8, wherein the selected stimulus signal has a minimum noise response.

10. An apparatus comprising

a processing device, the processing device configured to:

perform a listening scan on a sense array to compute an estimate of a noise metric;

induce, during the listening scan of the sense array, an injected touch signal, the injected touch signal induced, at the processing device, independent from signals received from the sense array;

measure a signal, wherein the measured signal comprises the injected touch signal and a second signal originating from the sense array;

convert the measured signal into first data; and

compute the estimate of the noise metric in the measured signal based on the injected touch signal, wherein computing the estimate of the noise metric comprises comparing the first data and second data corresponding to the injected touch signal, the second data representing expected data that would result from a conductive object proximate to a known location on a the sense array during a touch scan of the sense array.

11. The apparatus of claim 10, wherein the known location comprises a cell of a plurality of cells of the sense array where a detected touch proximate the sense array occurs.

12. The apparatus of claim 10, wherein the listening scan is performed independent of a transmitted stimulus signal.

13. The apparatus of claim 10, wherein the listening scan is performed for a plurality of frequencies.

14. The apparatus of claim 13, wherein the listening scan is performed for a plurality of frequencies in parallel.

15. The apparatus of claim 10, wherein the processing device is further configured to induce the injected touch internal to a receiving circuit, and wherein the processing device is further to process the data of the injected touch in an equivalent signal path to touch data from a touch proximate the sense array present during the touch scan of the sense array.

16. The apparatus of claim 15, further comprising a capacitance-sensing circuit comprising a receiving circuit.

17. The apparatus of claim 10, wherein the processing device is further to select a stimulus signal from a plurality of stimulus signals for the touch scan, wherein the touch scan measures the touch proximate the sense array, and wherein the selection of the stimulus signal is based on the noise metric, wherein the noise metric is indicative of noise characteristics of noise on the sense array.

18. The apparatus of claim 17, wherein the selected stimulus signal has a minimum noise response.

19. A system comprising:

a capacitive sense array configured to generate touch data for a touch detected proximate to the capacitive sense array, the touch data represented as a plurality of cells; and

a processing device coupled to the capacitive sense array, wherein the processing device is configured to;

perform a listening scan on the capacitive sense array to determine an estimate of a noise metric;

induce, during the listening scan of the capacitive sense array, an injected touch signal, the injected touch signal induced, at the processing device, independent from signals received from the capacitive sense array;

measure a signal, wherein the measured signal comprises the injected touch signal and a second signal originating from the capacitive sense array;

convert the measured signal into first data; and

compute the estimate of the noise metric in the measured signal based on the injected touch signal, wherein computing the estimate of the noise metric comprises comparing the first data and second data corresponding to the injected touch signal, the second data representing expected data that would result from a conductive object proximate to a known location on the capacitive sense array during a touch scan of the capacitive sense array.

20. The system of claim 19, wherein the processing device is further to

select a stimulus signal from a plurality of stimulus signals for the touch scan, wherein the touch scan measures the touch proximate the sense array, and wherein the selection of the stimulus signal is based on the noise metric.