Capacitive touch sensor with polarity normalization

• US 9,798,432 B2
• Filed: 10/13/2015
• Issued: 10/24/2017
• Est. Priority Date: 03/27/2015
• Status: Active Grant

• Current Assignee: Displax S.A.
• Original Assignee: Displax S.A.
• Inventors: Marques, Pedro Luis Fernandes, Fonseca, Miguel Angelo Magalhaes, Peixoto de Oliveira, Jos Miguel Fernandes, Babo de Carvalho, Antnio Augusto
• Primary Examiner(s): Nguyen, Kevin M
• Application Number:
  US14/882,003
• Publication Number:
  US 20160282986A1
• Time in Patent Office: 742 Days
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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

This application relates to a projected capacitive touch sensor with polarity normalization. The sensor includes a sensor grid including one or more electrically conductive rows and one or more electrically conductive columns. The sensor further includes a first column multiplexer that is connected to a first portion of the one or more electrically conductive columns. The sensor further includes a second column multiplexer that is connected to a second portion of the one or more electrically conductive columns. The sensor further includes a polarity switching circuit that is configured to determine a polarity of a differential signal generated from an output of the first column multiplexer and an output of the second column multiplexer, and based on determining the polarity of the differential signal, determining whether to switch the polarity of the differential signal.

Claims

1. A projected capacitive touch sensor, comprising:

a sensor grid including one or more electrically conductive rows and one or more electrically conductive columns;

a first column multiplexer that is connected to a first portion of the one or more electrically conductive columns;

a second column multiplexer that is connected to a second portion of the one or more electrically conductive columns;

a polarity switching circuit that is configured to;

receive a first address signal provided to the first column multiplexer;

receive a second address signal provided to the second column multiplexer;

compare the first address signal to the second address signal;

based on comparing the first address signal to the second address signal, determine a polarity of a differential signal generated from an output of the first column multiplexer and an output of the second column multiplexer; and

based on determining the polarity of the differential signal, determining whether to switch the polarity of the differential signal.

2. The sensor of claim 1, wherein the polarity switching circuit is configured to determine a polarity of the differential signal based on (i) a first location of a first electrically conductive column selected as the output of the first column multiplexer and (ii) a second location of a second electrically conductive column selected as the output of the second column multiplexer.

3. The sensor of claim 1, wherein the first portion of the one or more electrically conductive columns and the second portion of the one or more electrically conductive columns are interleaved.

4. The sensor of claim 1, wherein an electrically conductive column located on an edge of the sensor grid is connected to both the first column multiplexer and the second column multiplexer.

5. The sensor of claim 1, wherein:

determining the polarity of the differential signal comprises determining that the differential signal is based on the output of the first column multiplexer minus the output of the second column multiplexer, and

determining whether to switch the polarity of the differential signal comprises determining not to switch the polarity of the differential signal.

6. The sensor of claim 1, wherein:

determining the polarity of the differential signal comprises determining that the differential signal is based on the output of the second column multiplexer minus the output of the first column multiplexer, and

determining whether to switch the polarity of the differential signal comprises determining to switch the polarity of the differential signal.

7. The sensor of claim 1, comprising:

a third column multiplexer that is connected to a third portion of the one or more electrically conductive columns;

a fourth column multiplexer that is connected to a fourth portion of the one or more electrically conductive columns; and

an additional polarity switching circuit that is configured to;

determine a polarity of an additional differential signal generated from an output of the third column multiplexer and an output of the fourth column multiplexer; and

based on determining the polarity of the additional differential signal, determining whether to switch the polarity of the differential signal,

wherein a first block of consecutive electrically conductive columns of the sensor grid includes the first portion of the one or more electrically conductive columns and the second portion of the one or more electrically conductive columns, and

wherein a second block of consecutive electrically conductive columns of the sensor grid includes the third portion of the one or more electrically conductive columns and the fourth portion of the one or more electrically conductive columns.

8. The sensor of claim 7, wherein an electrically conductive column located in the first block is connected to both the first column multiplexer and the third column multiplexer.

9. The sensor of claim 7, wherein a first electrically conductive column selected as the output of the third column multiplexer is adjacent to a second electrically conductive column selected as the output of the fourth column multiplexer, the first electrically conductive column being located in the second block and the second electrically conductive column being located in the first block.

10. The sensor of claim 1, wherein the polarity switching circuit is a double pole double throw switch.

11. The sensor of claim 1, wherein a first electrically conductive column selected as the output of the first column multiplexer is adjacent to a second electrically conductive column selected as the output of the second column multiplexer.

12. The sensor of claim 1, wherein the first column multiplexer includes one more input than the second column multiplexer.

13. A method comprising:

determining a differential signal that is based on an output of a first column multiplexer and an output of a second column multiplexer, wherein the first column multiplexer is connected to a first portion of one or more electrically conductive columns of a sensor grid and the second column multiplexer is connected to a second portion of the one or more electrically conductive columns of the sensor grid;

receiving a first address signal provided to the first column multiplexer;

receiving a second address signal provided to the second column multiplexer;

comparing the first address signal to the second address signal;

based on comparing the first address signal to the second address signal, determining a polarity of the differential signal; and

based on determining the polarity of the differential signal, determining whether to switch the polarity of the differential signal.

14. The method of claim 13, wherein determining a polarity of the differential signal is based on (i) a first location of a first electrically conductive column selected as the output of the first column multiplexer and (ii) a second location of a second electrically conductive column selected as the output of the second column multiplexer.

15. The method of claim 13, wherein:

determining the polarity of the differential signal comprises determining that the differential signal is based on the output of the second column multiplexer minus the output of the first column multiplexer, and

determining whether to switch the polarity of the differential signal comprises determining to switch the polarity of the differential signal.

16. The method of claim 13, wherein a first electrically conductive column selected as the output of the first column multiplexer is adjacent to a second electrically conductive column selected as the output of the second column multiplexer.

17. The method of claim 13, comprising:

determining an additional differential signal that is based on an output of a third column multiplexer and an output of a fourth column multiplexer, wherein the third column multiplexer is connected to a third portion of one or more electrically conductive columns of a sensor grid and the fourth column multiplexer is connected to a fourth portion of the one or more electrically conductive columns of the sensor grid;

determining a polarity of the additional differential signal; and

based on determining the polarity of the additional differential signal, determining whether to switch the polarity of the additional differential signal,

wherein a first block of consecutive electrically conductive columns of the sensor grid includes the first portion of the one or more electrically conductive columns and the second portion of the one or more electrically conductive columns, and

wherein a second block of consecutive electrically conductive columns of the sensor grid includes the third portion of the one or more electrically conductive columns and the fourth portion of the one or more electrically conductive columns.

18. A method comprising:

receiving an output of a first column multiplexer and an output of a second column multiplexer, wherein the first column multiplexer is connected to a first portion of one or more electrically conductive columns of a sensor grid and the second column multiplexer is connected to a second portion of the one or more electrically conductive columns of the sensor grid;

receiving a bit of a first address signal provided to the first column multiplexer;

receiving a bit of a second address signal provided to the second column multiplexer;

comparing the bit of the first address signal provided to the first column multiplexer with the bit of the second address signal provided to the second column multiplexer; and

based on comparing the bit of the first address signal provided to the first column multiplexer with the bit of the second address signal provided to the second column multiplexer, determining whether to switch a polarity of a differential signal generated based on the output of the first column multiplexer and the output of the second column multiplexer.

19. The method of claim 18, wherein determining whether to switch a polarity of a differential signal generated based on the output of the first column multiplexer and the output of the second column multiplexer comprises determining to switch the polarity of the differential signal generated based on the output of the first column multiplexer and the output of the second column multiplexer in response to comparing the bit of the first address signal provided to the first column multiplexer that matches the bit of the second address signal provided to the second column multiplexer.

20. The method of claim 18, wherein determining whether to switch a polarity of a differential signal generated based on the output of the first column multiplexer and the output of the second column multiplexer comprises determining not to switch the polarity of the differential signal generated based on the output of the first column multiplexer and the output of the second column multiplexer in response to comparing the bit of the first address signal provided to the first column multiplexer that does not match the bit of the second address signal provided to the second column multiplexer.