Eliminating common mode noise in otuch applications

• US 9,110,552 B2
• Filed: 06/06/2013
• Issued: 08/18/2015
• Est. Priority Date: 03/11/2013
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Maharyta, Andriy, Karpin, Oleksandr, Boychuk, Yuriy, Ribeiro, Milton
• Primary Examiner(s): Sasinowski, Andrew
• Assistant Examiner(s): Truong, Nguyen H
• Application Number:
  US13/912,028
• Publication Number:
  US 20140253492A1
• Time in Patent Office: 803 Days
• Field of Search: 345173-178
• US Class Current: 1/1
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• 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 processing device scans, during a first operation, a first plurality of electrodes along a first axis in a capacitive sense array to generate a first plurality of signals corresponding to a mutual capacitance at electrode intersections of the capacitive sense array. During a second operation, the processing device scans a second plurality of electrodes along a second axis in the capacitive sense array to generate a second plurality of signals corresponding to the mutual capacitance at the electrode intersections of the capacitive sense array, wherein the second operation occurs during a different period of time than the first operation. The processing device determines a first coordinate of a conductive object proximate to the capacitive sense array based on the first plurality of signals and a second coordinate of the conductive object based on the second plurality of signals.

Claims

1. A method comprising:

scanning, during a first operation, a first plurality of electrodes along a first axis in a capacitive sense array to generate a first plurality of signals corresponding to a mutual capacitance at electrode intersections of the capacitive sense array, the first plurality of signals to identify a first coordinate of a conductive object proximate to the capacitive sense array;

scanning, during a second operation, a second plurality of electrodes along a second axis in the capacitive sense array to generate a second plurality of signals corresponding to the mutual capacitance at the electrode intersections of the capacitive sense array, the second plurality of signals to identify a second coordinate of the conductive object, wherein the second operation occurs during a different period of time than the first operation;

determining, by a processing device during a third operation, the first coordinate of the conductive object proximate to the capacitive sense array based on the first plurality of signals and the second coordinate of the conductive object based on the second plurality of signals, the first coordinate and the second coordinate comprising a first location of the conductive object on the capacitive sense array;

scanning, during the third operation, the first plurality of electrodes to generate a third plurality of signals, the third plurality of signals to identify a third coordinate of the conductive object, wherein each of the first plurality of electrodes are scanned during the third operation regardless of a result of the first and second; and

determining, during a fourth operation, a third coordinate of the conductive object based on the third plurality of signals, the second coordinate and the third coordinate comprising a second location of the conductive object on the capacitive sense array.

2. The method of claim 1, wherein scanning the first plurality of electrodes comprises:

driving one or more of the second plurality of electrodes along the second axis with a transmit signal; and

measuring a receive signal from the first plurality of electrodes along the first axis.

3. The method of claim 1, wherein scanning the second plurality of electrodes comprises:

driving one or more of the first plurality of electrodes along the first axis with a transmit signal; and

measuring a receive signal from the second plurality of electrodes along the second axis.

4. The method of claim 1, wherein the second operation occurs subsequent to the first operation and does not overlap in time with the first operation.

5. The method of claim 1, further comprising:

identifying a touch position equation, from a plurality of touch position equations, for use in determining the first coordinate and the second coordinate of the conductive object.

6. The method of claim 1, wherein the third coordinate corresponds to the first coordinate at a subsequent time.

7. The method of claim 1,

wherein the third plurality of electrodes overlaps the second plurality of electrodes by at least two electrodes.

8. An apparatus comprising:

a capacitive sense array; and

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

generate, during a first operation, a first plurality of signals from a first plurality of electrodes along a first axis in the capacitive sense array, the first plurality of signals corresponding to a mutual capacitance at electrode intersections of the capacitive sense array, the first plurality of signals to identify a first coordinate of a conductive object proximate to the capacitive sense array;

generate, during a second operation, a second plurality of signals from a second plurality of electrodes along a second axis in the capacitive sense array, the second plurality of signals corresponding to the mutual capacitance at the electrode intersections of the capacitive sense array, the second plurality of signals to identify a second coordinate of the conductive object, wherein the second operation occurs during a different period of time than the first operation;

determine, during a third operation, the first coordinate of the conductive object proximate to the capacitive sense array based on the first plurality of signals and the second coordinate of the conductive object based on the second plurality of signals, the first coordinate and the second coordinate comprising a first location of the conductive object on the capacitive sense array;

generate, during the third operation, a third plurality of signals from the first plurality of electrodes, the third plurality of signals to identify a third coordinate of the conductive object, wherein each of the first plurality of electrodes are scanned during the third operation regardless of a result of the first and second operations; and

determine, during a fourth operation, a third coordinate of the conductive object based on the third plurality of signals, the second coordinate and the third coordinate comprising a second location of the conductive object on the capacitive sense array.

9. The apparatus of claim 8, wherein to generate the first plurality of signals, the processing device is configured to:

drive one or more of the second plurality of electrodes along the second axis with a transmit signal; and

measure a receive signal from the first plurality of electrodes along the first axis.

10. The apparatus of claim 8, wherein to generate the second plurality of signals, the processing device is configured to:

drive one or more of the first plurality of electrodes along the first axis with a transmit signal; and

measure a receive signal from the second plurality of electrodes along the second axis.

11. The apparatus of claim 8, wherein the second operation occurs subsequent to the first operation and does not overlap in time with the first operation.

12. The apparatus of claim 8, wherein the processing device is further configured to:

identify a touch position equation, from a plurality of touch position equations, for use in determining the first coordinate and the second coordinate of the conductive object.

13. The apparatus of claim 8, wherein the third coordinate corresponds to the first coordinate at a subsequent time.

14. The apparatus of claim 8,

wherein the third plurality of electrodes overlaps the second plurality of electrodes by at least two electrodes.

15. An apparatus comprising:

a touch-sensor device, the touch-sensor device comprising an array of capacitive sense elements, the array comprising a plurality of transmit electrodes and a plurality of receive electrodes;

a transmit selection circuit coupled to the touch-sensor device, the transmit selection circuit to selectively apply a transmit signal to one or more of the transmit electrodes;

a receive selection circuit coupled to the touch-sensor device, the receive selection circuit to selectively measure a signal from one or more of the receive electrodes, wherein the measured signal corresponds to a mutual capacitance value between a transmit electrode and a receive electrode; and

a processing device coupled to the touch-sensor device, the processing device configured to;

measure, during a first operation, a capacitance value from the receive electrodes along a first axis in the capacitive sense array to determine a first coordinate of a conductive object proximate to the touch-sensor device;

switch an orientation of the transmit and receive electrodes;

measure, during a second operation, a capacitance value from the receive electrodes along a second axis in the capacitive sense array to determine a second coordinate of the conductive object, the first coordinate and the second coordinate comprising a first location of the conductive object on the touch-sensor device, wherein the second operation occurs during a different period of time than the first operation;

switch the orientation of the transmit and receive electrodes; and

measure, during a third operation, a capacitance value from the receive electrodes along the first axis to determine a third coordinate of the conductive object, wherein each of the receive electrodes are measured during the third operation regardless of a result of the first and second operations, the second coordinate and the third coordinate comprising a second location of the conductive object on the capacitive sense array.

16. The apparatus of claim 15, wherein to measure a capacitance value from the receive electrodes along the first axis, the processing device is configured to:

drive one or more of the transmit electrodes along the second axis with a transmit signal; and

measure a receive signal from the receive electrodes along the first axis.

17. The apparatus of claim 15, wherein to measure a capacitance value from the receive electrodes along the second axis, the processing device is configured to:

drive one or more of the transmit electrodes along the first axis with a transmit signal; and

measure a receive signal from the receive electrodes along the second axis.

18. The apparatus of claim 15, wherein the second operation occurs subsequent to the first operation and does not overlap in time with the first operation.

19. The apparatus of claim 15, wherein the processing device is further configured to:

identify a touch position equation, from a plurality of touch position equations, for use in determining the first coordinate and the second coordinate of the conductive object.

20. The apparatus of claim 15, wherein the processing device determines the first coordinate and the second coordinate during the third operation, and wherein the third coordinate corresponds to the first coordinate at a subsequent time.