USE OF RANDOM SAMPLING TECHNIQUE TO REDUCE FINGER-COUPLED NOISE

• US 20110261008A1
• Filed: 01/07/2011
• Published: 10/27/2011
• Est. Priority Date: 04/22/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Allen, David L., Viswanathan, Natarajan, Chan, Patrick, Joharapurkar, Ashutosh Ravindra
• Granted Patent: US 9,391,607 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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: H03K 17/96 Touch switches specially adapted for electronic time-pieces with no moving parts G04G21/08
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/96062 with tactile or haptic feedback

Abstract

Random sampling techniques include techniques for reducing or eliminating errors in the output of capacitive sensor arrays such as touch panels. The channels of the touch panel are periodically sampled to determine the presence of one or more touch events. Each channel is individually sampled in a round robin fashion, referred to as a sampling cycle. During each sampling cycle, all channels are sampled once. Multiple sampling cycles are performed such that each channel is sampled multiple times. Random sampling techniques are used to sample each of the channels. One random sampling technique randomizes a starting channel in each sampling cycle. Another random sampling technique randomizes the selection of all channels in each sampling cycle. Yet another random sampling technique randomizes the sampling cycle delay period between each sampling cycle. Still another random sampling technique randomizes the channel delay period between sampling each channel.

Claims

1. A method of detecting one or more touch events on a capacitive touch sensitive device comprising;

a. configuring a plurality of channels, each channel corresponding to the capacitive touch sensitive device;

b. sampling each channel in the plurality of channels according to a randomization algorithm;

c. for each channel, calculating a channel capacitance using sampled data; and

d. determining one or more touch events from the channel capacitances calculated for the plurality of channels.

2. The method of claim 1 wherein the randomization algorithm comprises performing multiple sampling cycles, each sampling cycle includes sampling each channel in the plurality of channels.

3. The method of claim 2 wherein the randomization algorithm further comprises starting each sampling cycle with a randomly selected channel.

4. The method of claim 3 wherein each channel in the plurality of channels is sampled in a predetermined sequential order, each sampling cycle starts at the randomly selected channel and sampling continues in the sequential order for a remainder of the sampling cycle.

5. The method of claim 2 wherein the randomization algorithm further comprises randomly selecting each channel within the sampling cycle.

6. The method of claim 2 wherein a sampling cycle delay period is included between each sampling cycle, further wherein the randomization algorithm comprises randomly changing the sampling cycle delay period between each sampling cycle.

7. The method of claim 2 wherein a channel delay period is included between each channel sampling, further wherein the randomization algorithm comprises randomly changing the channel delay period.

8. The method of claim 7 wherein the plurality of channels comprises N channels, and the randomization algorithm comprises randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples.

9. The method of claim 8 wherein M is less than N.

10. The method of claim 8 wherein M is greater than N.

11. The method of claim 2 wherein calculating the channel capacitance for each channel comprises averaging the measured capacitances from the multiple sampling cycles for the channel.

12. The method of claim 1 wherein each channel comprises either a row of touch sensors in the capacitive touch sensitive device or a column of touch sensors in the capacitive touch sensitive device.

13. The method of claim 1 wherein noise is distributed across a frequency response of the sampled channels.

14. The method of claim 1 wherein noise is distributed across multiple channels in the plurality of channels.

15. A method of detecting one or more touch events on a capacitive touch sensitive device comprising;

a. configuring a plurality of channels, each channel corresponding to the capacitive touch sensitive device;

b. sampling each channel in the plurality of channels according to a randomization algorithm such that each channel is sampled, wherein sampling each channel comprises measuring a capacitance of each channel;

c. performing multiple sampling cycles, wherein a sampling cycle comprises sampling each channel in the plurality of channels one time;

d. for each channel, calculating a channel capacitance using the measured capacitances from the multiple sampling cycles for the channel; and

e. determining one or more touch events from the channel capacitances calculated for the plurality of channels.

16. The method of claim 15 wherein the randomization algorithm comprises starting each sampling cycle with a randomly selected channel.

17. The method of claim 16 wherein each channel in the plurality of channels is sampled in a predetermined sequential order, each sampling cycle starts at the randomly selected channel and sampling continues in the sequential order for a remainder of the sampling cycle.

18. The method of claim 15 wherein the randomization algorithm comprises randomly selecting each channel within the sampling cycle.

19. The method of claim 15 wherein a sampling cycle delay period is included between each sampling cycle, further wherein the randomization algorithm comprises randomly changing the sampling cycle delay period between each sampling cycle.

20. The method of claim 15 wherein a channel delay period is included between each channel sampling, further wherein the randomization algorithm comprises randomly changing the channel delay period.

21. The method of claim 20 wherein the plurality of channels comprises N channels, and the randomization algorithm comprises randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples.

22. The method of claim 21 wherein M is less than N.

23. The method of claim 21 wherein M is greater than N.

24. The method of claim 15 wherein noise is distributed across a frequency response of the sampled channels.

25. The method of claim 15 wherein noise is distributed across multiple channels in the plurality of channels.

26. The method of claim 15 wherein calculating the channel capacitance for each channel comprises averaging the measured capacitances from the multiple sampling cycles for the channel.

27. The method of claim 15 wherein each channel comprises either a row sensor in the capacitive touch sensitive device or a column sensor in the capacitive touch sensitive device.

28. An apparatus for detecting one or more touch events on a touch panel comprising;

a. a capacitive touch sensitive device including a plurality of channels, each channel comprising a touch sensor;

b. a processor configured to implement a randomization algorithm; and

c. a measuring circuit coupled to the capacitive touch sensitive device and to the processor, wherein the measuring circuit is configured to sample each channel in the plurality of channels according to the randomization algorithm,

wherein the processor is configured to receive sampled data from the measuring circuit, to calculate a channel capacitance for each channel using the received sample data, and to determine one or more touch events from the channel capacitances calculated for the plurality of channels.

29. The apparatus of claim 28 wherein the randomization algorithm comprises performing multiple sampling cycles, each sampling cycle includes sampling each channel in the plurality of channels.

30. The apparatus of claim 29 wherein the randomization algorithm further comprises starting each sampling cycle with a randomly selected channel.

31. The apparatus of claim 30 wherein the processor and the measuring circuit are configured such that each channel in the plurality of channels is sampled in a predetermined sequential order, each sampling cycle starts at the randomly selected channel and sampling continues in the sequential order for a remainder of the sampling cycle.

32. The apparatus of claim 29 wherein the randomization algorithm further comprises randomly selecting each channel within the sampling cycle.

33. The apparatus of claim 29 wherein a sampling cycle delay period is included between each sampling cycle, further wherein the randomization algorithm comprises randomly changing the sampling cycle delay period between each sampling cycle.

34. The apparatus of claim 29 wherein a channel delay period is included between each channel sampling, further wherein the randomization algorithm comprises randomly changing the channel delay period.

35. The apparatus of claim 34 wherein the plurality of channels comprises N channels, and the randomization algorithm comprises randomly generating the channel delay period every M channel samples such that a same channel delay period is applied for each of M channel samples before a new channel delay period is randomly generated and applied to a next M channel samples.

36. The apparatus of claim 34 wherein M is less than N.

37. The apparatus of claim 34 wherein M is greater than N.

38. The apparatus of claim 28 wherein the processor is configured to calculate the channel capacitance for each channel by averaging the measured capacitances from the multiple sampling cycles for the channel.

39. The apparatus of claim 28 wherein each channel comprises either a row sensor in the capacitive touch sensitive device or a column sensor in the capacitive touch sensitive device.

40. The apparatus of claim 28 wherein the capacitive touch sensitive device comprises a two-dimensional touch panel.

41. The apparatus of claim 28 wherein the capacitive touch sensitive device comprises a one-dimensional virtual slider.

42. An apparatus for detecting one or more touch events on a touch panel comprising;

a. a capacitive touch sensitive device including a plurality of channels, each channel comprising a touch sensor;

b. a processor configured to implement a randomization algorithm; and

c. a measuring circuit coupled to the capacitive touch sensitive device and to the processor, wherein the measuring circuit is configured to sample each channel in the plurality of channels according to the randomization algorithm such that each channel is sampled, wherein sampling each channel comprises measuring a capacitance of each channel, and multiple sampling cycles are performed, wherein a sampling cycle comprises sampling each channel in the plurality of channels one time,

wherein the processor is configured to receive measured capacitance data from the multiple sampling cycles, to calculate a channel capacitance for each channel using the received measured capacitance data, and to determine one or more touch events from the channel capacitances calculated for the plurality of channels.