Use of random sampling technique to reduce finger-coupled noise

• US 9,391,607 B2
• Filed: 01/07/2011
• Issued: 07/12/2016
• Est. Priority Date: 04/22/2010
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Joharapurkar, Ashutosh Ravindra, Chan, Patrick, Allen, David L., Viswanathan, Natarajan
• Primary Examiner(s): XAVIER, ANTONIO J
• Application Number:
  US12/987,008
• Publication Number:
  US 20110261008A1
• Time in Patent Office: 2,013 Days
• Field of Search: None
• US Class Current: 1/1
• 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:

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

sampling each channel in the plurality of channels according to a randomization algorithm during a first sampling cycle, wherein a randomly selected channel is sampled at a start of the first sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after a defined channel delay period;

sampling, after a defined first sampling cycle delay period between the first sampling cycle and a second sampling cycle, each channel in the plurality of channels according to the randomization algorithm during the second sampling cycle, wherein a randomly selected channel is sampled at a start of the second sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after the defined channel delay period, wherein the defined first sampling cycle delay period is greater than the defined channel delay period;

sampling, after a defined second sampling cycle delay period between the second sampling cycle and a third sampling cycle, each channel in the plurality of channels according to the randomization algorithm during the third sampling cycle, wherein a randomly selected channel is sampled at a start of the third sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after the defined channel delay period, wherein the defined second sampling cycle delay period is greater than the defined channel delay period, wherein the defined second sampling cycle delay period is equal to the defined first sampling cycle period;

matching sampled data sampled during the first sampling cycle for each channel of the plurality of channels to the sampled data sampled during the second sampling cycle and the third sampling cycle for the same channel;

for each channel, calculating a channel capacitance using sampled data, wherein calculating the channel capacitance for each channel comprises averaging the sampled data for each channel over multiple cycles; and

determining one or more touch events based upon the channel capacitances calculated for the plurality of channels,

wherein each channel in the plurality of channels is sampled in a sequential order during the first sampling cycle, the second sampling cycle, and the third sampling cycle.

2. 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.

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

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

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

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;

performing a first sampling cycle, wherein the first sampling cycle comprises sampling each channel in the plurality of channels, wherein a randomly selected channel is sampled at a start of the first sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after a defined channel delay period;

performing a second sampling cycle after a defined sampling cycle delay period, wherein the second sampling cycle comprises sampling each channel in the plurality of channels, wherein a randomly selected channel is sampled at a start of the second sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after the defined channel delay period, wherein the defined sampling cycle delay period is greater than the channel delay period;

matching sampled data sampled during the first sampling cycle for each channel of the plurality of channels sampled to the sampled data sampled during the second sampling cycle for the same channel;

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

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

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 4 wherein noise is distributed across a frequency response of the sampled channels.

6. The method of claim 4 wherein each channel comprises either a row sensor in the capacitive touch sensitive device or a column sensor in the capacitive touch sensitive device.

7. An apparatus for detecting one or more touch events on a touch panel comprising:

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

a processor configured to implement a randomization algorithm; and

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 during a first sampling cycle according to the randomization algorithm and to sample each channel in the plurality of channels during a second sampling cycle after a defined sampling cycle delay period according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after a defined channel delay period, wherein the defined sampling cycle delay period is greater than the defined channel delay period, wherein a randomly selected channel is sampled at a start of each sampling cycle according to the randomization algorithm, wherein the processor is configured to receive sampled data from the measuring circuit, to match sampled data sampled during a first sampling cycle for each channel of the plurality of channels to the sampled data sampled during a second sampling cycle for the same channel, 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, wherein the processor is configured to calculate the channel capacitance for each channel by averaging the sampled data for each channel over multiple cycles;

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.

8. The apparatus of claim 7 wherein each channel comprises either a row sensor in the capacitive touch sensitive device or a column sensor in the capacitive touch sensitive device.

9. The apparatus of claim 7 wherein the capacitive touch sensitive device comprises a two- dimensional touch panel.

10. The apparatus of claim 7 wherein the capacitive touch sensitive device comprises a one-dimensional virtual slider.

11. An apparatus for detecting one or more touch events on a touch panel comprising:

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

a processor configured to implement a randomization algorithm; and

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 during a first sampling cycle according to the randomization algorithm such that each channel is sampled and to sample each channel in the plurality of channels during second sampling cycle after a defined sampling cycle delay period according to the randomization algorithm such that each channel is sampled, wherein a randomly selected channel is sampled at a start of each sampling cycle according to the randomization algorithm, wherein each channel in the plurality of channels is sampled after a defined channel delay period, wherein the defined sampling cycle delay period is greater than the defined channel delay period, 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 match sampled data sampled during a first sampling cycle for each channel of the plurality of channels to the sampled data sampled during a second sampling cycle for the same channel, 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, wherein the processor is configured to calculate the channel capacitance for each channel by averaging the sampled data for each channel over multiple cycles;

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.