Water robustness and detection on capacitive buttons

Patent metadata

Field	Value
Publication number	US-10146371-B2
Application number	US-201715471322-A
Country	US
Kind code	B2
Filing date	Mar 28, 2017
Priority date	Mar 29, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A method for touch detection includes identifying a high-pass filtered sequence from a plurality of sensor measurements, accumulating a number of samples from a first high-pass filtered sequence into an accumulated value, comparing the first accumulated value against a threshold of accumulated values, and, based upon a determination whether the accumulated value is greater than the threshold of accumulated values, identify whether the sensor has been approached.

First claim

The invention claimed is:

1. At least one non-transitory computer-readable medium containing instructions, the instructions, when loaded and executed by a processor, cause the processor to:
identify a first high-pass filtered sequence from a plurality of sensor measurements;
accumulate a plurality of samples from the first high-pass filtered sequence into a first accumulated value;
compare the first accumulated value against a first threshold of accumulated values;
based upon a determination whether the first accumulated value is greater than the first threshold of accumulated values, identify whether the sensor has been approached;
reset the first accumulated value when:
the first high-pass filtered sequence changes its sign; or
a result of low-pass filtering the high-pass filtered sequence changes its sign;

count a number of resets of the first accumulated value, wherein a given reset occurred after the first accumulated value exceeded an accumulation threshold during a defined time interval; and
determine, through comparing the number of resets of the accumulated value within the defined time interval to a counting threshold, whether moving moisture is present on the sensor.

2. The medium of claim 1 , further comprising instructions for causing a first low-pass filtering of the sensor measurements before or after the high-pass filtering.

3. The medium of claim 1 , further comprising instructions for causing the processor to:
identify a second high-pass filtered sequence from the plurality of sensor measurements;
accumulate a plurality of samples from the second high-pass filtered sequence into a second accumulated value;
compare the second accumulated value against a second threshold of accumulated values; and
based upon a determination whether the second accumulated value is greater than the second threshold of accumulated values, identify whether the sensor has been approached.

4. The medium of claim 1 , where the first high-pass filtered sequence is computed by computing a sequence of differentials between sensor measurements.

5. The medium of claim 1 , further comprising instructions for causing the processor to reset the first accumulated value when the high-pass filtered sequence reaches a reset threshold.

6. The medium of claim 1 , further comprising instructions for causing the processor to:
input the high-pass filtered sequence into a Schmitt trigger with user-defined trigger hysteresis thresholds, wherein the first accumulated value is reset when the Schmitt trigger output is in one pre-defined level of a possible two output levels.

7. The medium of claim 1 , further comprising instructions for causing the processor to determine, through the sensor measurements, whether moving moisture is present on the sensor.

8. The medium of claim 1 , further comprising instructions for causing the processor to debounce the identification of whether the sensor has been approached based on whether moving moisture is present on the sensor.

9. The medium of claim 1 , further comprising instructions for causing the processor to debounce the identification of whether the sensor has been approached based on whether the first accumulated value has decreased.

10. The medium of claim 1 , further comprising instructions for causing the processor to extend a time for debouncing the identification of whether the sensor has been approached based on whether moving moisture is present on the sensor.

11. An apparatus, comprising:
a processor; and
at least one non-transitory computer-readable medium containing instructions, the instructions, when loaded and executed by a processor, cause the processor to:
identify a first high-pass filtered sequence from a plurality of sensor measurements;
accumulate a plurality of samples from the first high-pass filtered sequence into a first accumulated value;
compare the first accumulated value against a first threshold of accumulated values;
based upon a determination whether the first accumulated value is greater than the first threshold of accumulated values, identify whether the sensor has been approached;
count a number of resets of the first accumulated value, wherein a given reset occurred after the first accumulated value exceeded an accumulation threshold during a defined time interval; and
determine, through comparing the number of resets of the accumulated value within the defined time interval to a counting threshold, whether moving moisture is present on the sensor.

12. The apparatus of claim 11 , further comprising instructions for causing a first low-pass filtering of the sensor measurements before or after the high-pass filtering.

13. The apparatus of claim 11 , further comprising instructions for causing the processor to:
identify a second high-pass filtered sequence from the plurality of sensor measurements;
accumulate a plurality of samples from the second high-pass filtered sequence into a second accumulated value;
compare the second accumulated value against a second threshold; and
based upon a determination whether the second accumulated value is greater than the second threshold, identify whether the sensor has been approached.

14. The apparatus of claim 11 , where the first high-pass filtered sequence is computed by computing a sequence of differentials between sensor measurements.

15. The apparatus of claim 11 , further comprising instructions for causing the processor to reset the first accumulated value when:
the first high-pass filtered sequence changes its sign; or
a result of low-pass filtering the high-pass filtered sequence its sign.

16. The apparatus of claim 11 , further comprising instructions for causing the processor to reset the first accumulated value when high-pass filtered sequence reaches a reset threshold.

17. The apparatus of claim 11 , further comprising instructions for causing the processor to:
input the high-pass filtered sequence into a Schmitt trigger with user-defined trigger hysteresis thresholds, wherein the first accumulated value is reset when the Schmitt trigger output is in one pre-defined level of a possible two output levels.

18. The apparatus of claim 11 , further comprising instructions for causing the processor to determine, through the sensor measurements, whether moving moisture is present on the sensor.

19. The apparatus of claim 11 , further comprising instructions for causing the processor to debounce the identification of whether the sensor has been approached based on whether moving moisture is present on the sensor.

20. The apparatus of claim 11 , further comprising instructions for causing the processor to debounce the identification of whether the sensor has been approached based on whether the first accumulated value has decreased.

21. The apparatus of claim 11 , further comprising instructions for causing the processor to extend a time for debouncing the identification of whether the sensor has been approached based on whether moving moisture is present on the sensor.

22. A method for detecting proximity, comprising:
identifying a first high-pass filtered sequence from a plurality of sensor measurements;
accumulating a plurality of samples from the first high-pass filtered sequence into a first accumulated value;
comparing the first accumulated value against a first threshold of accumulated values;
based upon a determination whether the first accumulated value is greater than the first threshold of accumulated values, identifying whether t

Assignees

• Microchip Tech Germany Gmbh
• Microchip Tech Inc

Inventors

• Heim Axel
• Ferreira Joao

Classifications

• G06F2203/04108

  Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction · CPC title

• G06F3/0418 Primary

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/0441 Primary

  using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals · CPC title