Method and apparatus for reducing noise in capacitive touch interfaces

• US 9,256,333 B2
• Filed: 04/15/2014
• Issued: 02/09/2016
• Est. Priority Date: 04/15/2014
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Singh, Ramya Bagavath, Naik, Sudhir
• Primary Examiner(s): Moon, Seokyun
• Application Number:
  US14/253,302
• Publication Number:
  US 20150293621A1
• Time in Patent Office: 665 Days
• Field of Search: None
• 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 3/044 by capacitive means

Abstract

A method for controlling a capacitive touch panel includes filtering differential capacitance data. The filtered data is integrated in a first direction of the touch panel to generate a first set of integrated data, and integrated in a second direction of the touch panel to generate a second set of integrated data. The first and second sets of integrated data are averaged, and a touch on the touch panel is detected based on the average of the first and second sets of integrated touch data.

Claims

1. A method of reducing noise in a capacitive touch sensing system, the method comprising:

receiving differential touch data corresponding to values of a plurality of differential sensing nodes of a touch panel;

filtering the touch data;

performing integration of the filtered touch data with respect to a reference node from a first end and a second end;

calculating a weighted average of the integrated touch data measured at the first end and the second end; and

detecting a touch on the touch panel based on the calculated weighted average of the integrated touch data.

2. The method as claimed in claim 1, wherein filtering the touch data comprises performing median filtering of the differential touch data to reduce noise in the touch data.

3. The method as claimed in claim 2, wherein filtering the touch data further comprises performing exponential filtering of the median filtered data to reduce noise in the median filtered data.

4. The method as claimed in claim 1, wherein integrating the filtered data from the first end comprises performing cumulative addition of the filtered touch data from a left side with one reference node at a left end.

5. The method as claimed in claim 4, wherein integrating the filtered data from the second end comprises performing cumulative subtraction of the filtered touch data from a right side with one reference node at a right end.

6. The method as claimed in claim 5, further comprising:

obtaining integrated data with minimal noise by taking an average of the integrated data using one of linear weights or non-linear weights.

7. The method as claimed in claim 6, wherein the weights used for the weighted averaging varies linearly based on location of one or more sensor electrodes with respect to the first end and the second end.

8. The method as claimed in claim 6, wherein, for data obtained by integration from the left side, nodes on the left side include high weight values in a descending pattern towards the right nodes.

9. The method as claimed in claim 6, wherein, for data obtained by integration from the right side, nodes on the left side include low weight values in an ascending pattern towards the right nodes.

10. An apparatus for reducing noise in a capacitive touch sensing system, the apparatus comprising:

an input interface to provide differential touch data corresponding to values of a plurality of differential sensing nodes associated with a touch panel;

a noise filter to filter the touch data to reduce noise;

an integrator module to integrate the filtered touch data with respect to a reference node from a first end and a second end; and

a linear weighted averaging filter to calculate a weighted average of the integrated touch data measured at the first end and the second end.

11. The apparatus as claimed in claim 10, wherein the noise filter includes a median filter and an exponential averaging filter.

12. A method for controlling a capacitive touch panel, comprising:

filtering differential capacitance data;

integrating the filtered data in a first direction of the touch panel to generate a first set of integrated data;

integrating the filtered data in a second direction of the touch panel to generate a second set of integrated data;

averaging the first and second sets of integrated data; and

detecting a touch on the touch panel based on the average of the first and second sets of integrated touch data.

13. The method as claimed in claim 12, wherein the differential capacitance data is based on values of a differential sensing node of the touch panel.

14. The method as claimed in claim 12, wherein filtering the differential capacitance data includes:

median averaging the differential capacitance data to achieve a first level of noise reduction; and

exponential averaging the median-averaged data to achieve a second level of noise reduction, wherein the filtered data to be integrated in each of the first and second directions is based on the exponentially averaged data.

15. The method as claimed in claim 12, wherein the first direction is from a left side to a right side of the touch panel.

16. The method as claimed in claim 15, wherein the second direction is from the right side to the left side of the touch panel.

17. The method as claimed in claim 12, wherein averaging the first and second sets of integrated data includes calculating a weighted average of the first and second sets of integrated data.

18. The method as claimed in claim 12, wherein the weighted average is calculated based on weight values that change over time.

19. The method as claimed in claim 18, wherein the weight values change exponentially over time.

20. The method as claimed in claim 12, wherein:

averaging the first set of integrated data is performed based on weight values that increase in the first direction; and

averaging the second set of integrated data is performed based on weight values that decrease in the second direction.