001-92239_AN92239_Proximity_Sensing_with

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Document No. 001-92239 Rev. *B

AN92239

Proximity Sensing with CapSense

Author: Chethan

Associated Project: Yes

Associated Part Family: PSoC

4 Series

Software Version:

PSoC Creator™ 3.2 SP1 or later

Related Application Notes: For a complete list,

click here

To get the latest version of this application note, or the associated project file, please
visit

http://www.cypress.com/AN92239

AN92239 shows how to implement capacitive proximity-sensing applications using PSoC

CapSense

. It explains how

to  design  a  proximity  sensor  and  tune  it  to  achieve  a  large  proximity-sensing  distance  and  liquid-tolerant  proximity
sensing.  This  application  note  also  explains  how  to  implement  gesture  detection  based  on  proximity  sensing  and  the
wake-on-approach  method  to  reduce  device  power  consumption.  Example  projects  demonstrate  tuning  proximity
sensors  for  a  large  proximity-sensing  distance  and  liquid  tolerance,  and  implementing  gesture  detection  for  PSoC  4
series devices.

Contents

Introduction ............................................................... 2

Proximity Sensing with CapSense ............................ 2

Proximity-Sensing Applications Based on CapSense

Implementing Proximity Sensing with CapSense ..... 5

Challenges in Implementing Proximity Sensing

Based on CapSense ......................................................... 8

Layout Guidelines ..................................................... 8

6.1

Sensor Design ................................................. 8

6.2

Sensor Size ..................................................... 9

6.3

Sensor Layout ................................................ 10

Tuning CapSense CSD Parameters for a Large

Proximity-Sensing Distance ............................................ 11

7.1

Set Optimum CapSense CSD Parameters .... 11

7.2

Ensure SNR is Greater Than or Equal to 5:1 . 13

7.3

Set Optimum Threshold Parameters ............. 15

Firmware Filters for Reducing Noise ...................... 15

8.1

Advanced Low-Pass Filter ............................. 15

Tuning for Liquid Tolerance .................................... 17

9.1

Implementing Gesture Detection with Proximity

Sensors ...................................................................... 20

9.2

Sensor Design and Placement ...................... 20

9.3

Sensor Tuning ............................................... 20

9.4

Firmware Design ........................................... 20

Design Consideration to Achieve 30-cm Proximity-

Sensing Distance ............................................................ 21

Implementing Low-Power Systems Using the Wake-

on-Approach.................................................................... 22

Implementing the Wake-on-Approach Using Sensor

Ganging .......................................................................... 24

Example Projects ................................................... 26

13.1

Example Project 1

– Proximity Distance ........ 26

13.2

Example Project 2

– Liquid-Tolerant Proximity

13.3

Example Project 3

– Proximity Gestures ....... 33

Glossary ................................................................. 38

Summary ................................................................ 42

Document History ............................................................ 61

Worldwide Sales and Design Support ............................. 62

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Document No. 001-92239 Rev. *B

Introduction

A proximity sensor detects the presence of a nearby object without any physical contact. There are various types of
proximity sensors such as capacitive, inductive, magnetic, Hall effect, optical, and ultrasonic sensors, each of which
has its own advantages and disadvantages. Capacitive proximity sensing has gained huge popularity because of its
low cost, high reliability, low power, sleek aesthetics, and seamless integration with existing user interfaces.

Cyp

ress’s CapSense devices support self-capacitance based proximity sensing and can achieve up to a 30-cm

proximity-sensing distance. The process of setting CapSense Sigma Delta (CSD) parameters to achieve optimum
performance is called

“tuning.” See

Tuning CapSense CSD Parameters for a Large Proximity-Sensing Distance.

This application note explains how to:



Design a proximity sensor and tune the CSD parameters to achieve large proximity-sensing distances



Tune the CSD parameters for a proximity sensor to achieve liquid tolerance



Implement proximity-based gesture detection



Implement the wake-on-approach feature to reduce the power consumption of the device

Example Projects

demonstrate tuning for the maximum proximity-sensing distance, tuning for liquid tolerance, and

implementing proximity-based gesture detection. These example projects are designed to operate on the

CY8CKIT-

024 CapSense Proximity Shield

with the

CY8CKIT-040 PSoC 4000 Pioneer Kit

or the

CY8CKIT-042 PSoC 4 Pioneer

Kit

This application note is for advanced CapSense users. I

t assumes that you are familiar with Cypress’s CapSense

technology. If you are new to CapSense technology, refer to the

Getting Started with CapSense

design guide to learn

the basics of CapSense technology. To learn the basics of proximity sensing based on CapSense, refer to the
“Proximity Sensing” section in the

Getting Started with CapSense

design guide. To learn about the implementation of

CapSense technology in a specific device family, refer to the device-specific CapSense design guides available at

CapSense Design Guides

The initial sections of this application note cover the basics of tuning a proximity sensor and implementing gesture
detection. If you want to evaluate the example projects, proceed to the

Example Projects

section

Proximity Sensing with CapSense

The proximity-sensing technique based on CapSense involves measuring the change in the capacitance of a
proximity sensor when a target object approaches the sensor. The target object can be a human finger, hand, or any
conductive object. Proximity sensors based on CapSense can be constructed using a conductive (usually copper or
indium tin oxide) pad or trace laid on a nonconductive material like PCB or glass. The intrinsic capacitance of the
PCB trace or other connections to a capacitive sensor results in a sensor parasitic capacitance (C

When a proximity sensor based on CapSense is excited by a voltage source, an electric field is created around the
sensor. A small number of electric field lines couple to the nearby ground, while most of the electric field lines are
projected into the nearby space, as shown in

Figure 1

Figure 1. Proximity Sensing

PCB

Ground

Overlay

Proximity

Sensor

= C

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Document No. 001-92239 Rev. *B

When a target object approaches the sensor, some of the electric field lines couples to the target object and add a
small amount of finger capacitance (C

) to the existing C

, as shown in

Figure 2

. This change in capacitance is

measured by the CapSense circuitry to detect the proximity of the target object.

Figure 2. Electric Field Lines Coupling to Finger

PCB

Ground

Overlay

Proximity

Sensor

= C

+ C

= Total capacitance measured by the proximity-sensing system based on CapSense

= Sensor parasitic capacitance

= Capacitance added by a nearby target object

Proximity-Sensing Applications Based on CapSense

Proximity sensing based on CapSense is used in a variety of applications such as the following:



Face detection in mobile phones and tablets



Specific absorption rate (SAR) regulation in tablets and mobile phones



Wake-on-approach feature in battery-powered applications



Gesture detection in a human-machine interface (HMI)



Replacement for infrared (IR) sensors in applications such as automatic door openers, backlight control in control

panels, towel dispensers, faucets, and soap dispensers

Face detection in mobile phones and tablets

: Face detection is a feature in mobile phones that disables the

phone’s touchscreen and dims the brightness of the display when a user answers a phone call, as

Figure 3

shows.

Face detection prevents false touches when the phone is placed on the ear and optimizes the device

’s power

consumption. Using proximity sensing based on CapSense in this application offers advantages over IR proximity
sensing because it does not require cutouts in the overlay material, which reduces the tooling cost and improves the
aesthetics of the end product.

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Document No. 001-92239 Rev. *B

Figure 3. Face Detection in Mobile Phones

SAR regulation in tablets and mobile phones:

SAR is a measure of the rate at which energy is absorbed by the

human  body  when  exposed  to  an  RF  electromagnetic  field.  Regulatory  bodies  like  the  Federal  Communications
Commission  (FCC)  require  devices  to  limit  the  absorption  of  RF  energy  by  reducing  the  RF  transmit  power  of  the
device  when  the  device  is  in  close  proximity  to  the  human  body,  as

Figure 4

shows. Proximity sensors based on

CapSense can be used to detect the proximity of the human body and reduce RF power.

Figure 4. SAR Regulation in Tablets

Wake-on-approach:

This feature activates the system from the sleep or standby mode when an object approaches

the system, as

Figure 5

shows. Wake-on-approach is also used to control the backlight LEDs when the user

approaches the system. This feature reduces system wakeup time, improves device responsiveness, reduces device
power consumption, and improves aesthetics. It is useful in battery-operated applications such as mice and
keyboards.

Figure 5. Wake-on-Approach Implemented in a Mouse

Gesture detection:

Gesture detection is the technique of interpreting human body movements and providing

gesture-type information to the device. Gesture-based user interfaces provide an intuitive way for the user to interact
with the system, improving the user experience. Gesture detection is used in applications such as laptops, tablets,
and mobile phones for controlling the user interface.

Proximity sensors based on CapSense can be used in these applications to detect gestures without any physical
contact between the user and the device.

Figure 6

shows an example of an implementation of gesture detection in a

laptop where proximity sensors placed near the trackpad are used for the pan movement of the onscreen map.

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Document No. 001-92239 Rev. *B

Figure 6. Gesture Detection Implementation in a Laptop

IR replacement:

Proximity sensors based on CapSense can replace IR proximity sensors in applications such as

faucets and soap dispensers, as

Figure 7

shows

Proximity sensing based on CapSense offers the following advantages over IR proximity sensing:



It is a low-cost solution compared to IR proximity sensing. Proximity sensors based on CapSense can be

constructed using a copper trace on the PCB, whereas IR proximity sensing requires extra IR sensors.



Proximity sensors based on CapSense do not require any cutout in the overlay material to detect proximity

sensing, unlike IR proximity sensors. Therefore, proximity sensing based on CapSense reduces the tooling cost
and improves the aesthetics of the end product.



They consume less power than IR proximity sensors.



They are immune to ambient light, whereas IR-based proximity sensors can have performance issues with

varying ambient light.

Figure 7. Proximity Sensing Based on CapSense in a Soap Dispenser

Implementing Proximity Sensing with CapSense

Figure 8

shows the steps for designing a proximity-sensing system based on CapSense.

Understand proximity sensing:

See the

“Proximity Sensing” section in the

Getting Started with CapSense

design guide for an explanation of how proximity sensing based on CapSense works and a description of the
parameters that affect the proximity-sensing distance.

Evaluate how proximity sensing works:

Use

Cypress’s CY8CKIT-024 CapSense Proximity Shield.

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Document No. 001-92239 Rev. *B

Specify the proximity-sensing requirements:

After evaluating the proximity sensor performance, specify the

proximity-sensing requirements such as the required proximity-sensing distance, area available on the PCB for
sensor construction, system power consumption requirements, and EMI/ESD performance. These requirements
help you to select the right CapSense device and design the sensor layout.

Select the right CapSense device:

After the requirements are finalized, refer to the

“CapSense Selector Guide”

chapter in the

Getting Started with CapSense

design guide to select the right CapSense device based on the

required proximity-sensing distance.

Design the schematic and layout:

After selecting the CapSense device, design the schematic and layout. See

Layout Guidelines

, the device datasheet, and device-specific

CapSense Design Guides

Build the prototype:

After the schematic and layout design is completed, build the prototype of the design to

check if the design meets the performance requirements.

Tune:

Tune the prototype board to achieve the required performance. See

Tuning CapSense CSD Parameters

for a Large Proximity-Sensing Distance

and device-specific

CapSense Design Guides

After tuning the sensor, check if the proximity sensor performance meets the requirements. If the requirements
are met, proceed to

Step 11

otherwise continue with

Step 8

Redesign if necessary:

If the proximity sensor does not provide the required performance after you have set

the optimum parameters, increase the sensor size or reduce the noise in the system by shielding the sensor from
noise sources and continue with

Step 9.

Retune:

After redesigning the proximity sensor, retune the sensor and check if the sensor performance meets

the requirements. If the requirements are met, proceed to

Step 11

; otherwise continue with

Step 10.

10.

Revisit the design or requirements:

If the proximity sensor does not meet the required performance even after

you have changed the sensor dimensions to the maximum possible value and tuned it with the optimum
parameters, you need to revisit the requirements.

If you are not able to achieve the required proximity-sensing distance, select a device that has a better proximity
performance than the current device.

If you are not able to achieve the required proximity-sensing distance even with the best device, you need to
change the proximity sensor requirements, such as the area available for the sensor or the required proximity-
sensing distance, and repeat the procedure from

Step 3

11.

Proceed to mass production:

If the proximity sensor meets the required performance, you can proceed to

mass production.

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Document No. 001-92239 Rev. *B

Figure 8. Design Flow of a Proximity-Sensing System Based on CapSense

Start

Evaluate the Proximity

Sensing using a kit

Understand the Basics

of Proximity Sensing

Specify Proximity

Sensing Requirements

Study Feasibility and

Select Part

Design CapSense

schematic, Layout and

Mechanical Structure

Proximity

Performance is

Satisfactory?

Build Prototype

Tune the Prototype

Mass Production

End

Tune the Prototype

Proximity

Performance is

Satisfactory?

Increase Sensor Size or

Reduce Noise in the

System

Re-visit Proximity

Requirements

Yes

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Document No. 001-92239 Rev. *B

Challenges in Implementing Proximity Sensing Based on CapSense

As a designer, you may face several challenges, such as the following, when implementing a proximity-sensing
system based on CapSense.



Achieving a large proximity-sensing distance:

Proximity-sensing applications based on CapSense require a

proximity-sensing distance of 1 to 20 cm. Achieving a large proximity-sensing distance in an end system is a
challenge because the proximity-sensing distance depends on various factors such as the sensor layout, sensor
tuning, presence of noise sources, and floating or grounded conductive objects. Refer to the

“Proximity Sensing”

section in the

Getting Started with CapSense

design guide for a detailed explanation of the factors that affect the

proximity-sensing distance.



Reducing the noise:

Proximity sensors are more susceptible to noise because of their large sensor area and

high-sensitivity setting. High noise makes it difficult to achieve a signal-to-noise ratio (SNR) greater than 5:1,
which is required for reliable proximity sensing.



Implementing liquid-tolerant proximity sensing:

Proximity sensors are used in applications such as faucets

and soap dispensers. These applications require a robust operation even in the presence of water droplets and
other liquids. In these applications, the proximity sensor should be carefully tuned to avoid false triggers when
liquid droplets fall on the proximity sensor.



Implementing gesture detection with proximity sensors:

Reliable gesture detection based on proximity

sensing requires a large proximity-sensing distance. Choosing the right type of proximity sensor, sensor size,
and sensor placement plays an important role in implementing a reliable gesture detection system.

Layout Guidelines

The sensor layout plays a crucial role in achieving the required proximity-sensing distance. Following the layout best
practices helps in achieving low sensor C

, a large proximity-sensing distance, and low power consumption. A

proximity sensor with a low C

value has a high sensitivity and a large proximity-sensing distance.

6.1

Sensor Design

Proximity sensors can be constructed using one of the following methods:



Button sensor



Sensor ganging



PCB trace



Wire loop

These sensor implementation methods are explained in detail in the

“Proximity Sensing” section in the

Getting

Started with CapSense

design guide. Selection of the sensor type depends on the required proximity-sensing

distance and the area available for the sensor on the PCB.

Table 1

shows when to select a particular sensor

implementation method.

Table 1. Selecting the Proximity Sensor Type

Proximity

Sensor Type

When to Use

Button sensor

Use this method when the required proximity-sensing distance or the area available for
the sensor is very small.

Sensor
ganging

Use this method when there is no sensor pin or area available on the PCB for
implementing a proximity sensor. Ganging sensors can achieve a larger proximity-
sensing distance compared to using button sensors. See

Implementing the Wake-on-

Approach Using Sensor Ganging

PCB trace

Use this method when the required proximity-sensing distance is very large. This
method is preferred in most cases.

Wire loop

Use this method when the required proximity-sensing distance is very large. This
method has the disadvantage of higher manufacturing cost compared to the
implementation with PCB trace.

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Document No. 001-92239 Rev. *B

6.2

Sensor Size

The proximity sensor size depends on various factors such as the required proximity-sensing distance, presence of
noise sources, and floating or grounded conductive objects. Noise sources and floating or grounded conductive
objects reduce the SNR and the proximity-sensing distance. Therefore, large proximity sensors are needed to
achieve the proximity-sensing distance required in your design.

It is very difficult to derive a relationship between the sensor size and the  proximity-sensing distance. Depending on
the  end-system  environment,  the  proximity-sensing  distance  may  vary  for  a  specific  sensor  size.  You  can  find  the
sensor size required to achieve a  required proximity-sensing distance by making sensor prototypes. You can use a
copper foil, as

Figure 9

shows, to make a quick sensor prototype to determine the sensor size required to achieve the

required proximity-sensing distance.

Figure 9. Proximity Sensor Prototype Using Copper Tape on a Plastic Substrate

As a rule of thumb, start with a sensor loop diameter (in the case of a circular loop) or a diagonal (in the case of a
square loop) equal to the required proximity-sensing distance. If you are not able to achieve the required proximity-
sensing distance with this design, you can increase the sensor loop diameter or diagonal until the required proximity-
sensing distance is achieved.

For a loop sensor, the minimum recommended width of the PCB trace is 1.5 mm. For a wire-loop sensor, you can
use either a single-stranded or multistranded wire as the proximity sensor. The thickness of the wire has a very small
impact on the proximity-sensing distance.

Table 2

summarizes the proximity sensor layout guidelines. If the area available for the proximity sensor is less than

the area required to achieve the required proximity-sensing distance, you can implement firmware filters such as the

Advanced Low-Pass Filter

(ALP). The ALP filter attenuates the noise in the sensor raw count and increases the SNR.

An increase in SNR results in a large proximity-sensing distance.

Table 2. Proximity Sensor Layout Recommendations

Details

Minimum

Recommendation

Proximity sensor loop
diameter or diagonal

The sensor loop diameter or diagonal should
at least be equal to the required proximity-
sensing distance if the ALP filter is disabled.

If the ALP filter is enabled, the sensor loop
diameter or diagonal should at least be equal
to half of the required proximity-sensing
distance.

Start with a sensor loop diameter or diagonal
equal to the required proximity-sensing
distance and increase the diameter or diagonal
until the required proximity-sensing distance is
achieved.

Proximity sensor trace
width

1.5 mm

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Document No. 001-92239 Rev. *B

6.3

Sensor Layout

Keep the

following points in mind while designing the proximity sensor layout:



Maximize the size of the sensor:

The proximity-sensing distance is directly proportional to the sensor area. The

larger the proximity sensor area, the larger the proximity-sensing distance. However, a large sensor area results
in a high sensor C

and high noise, and thus reduces the proximity-sensing distance. Using a loop sensor

instead of a solid-fill sensor results in a low sensor C

, low noise and thus a large proximity-sensing distance.

Also, loop sensors require less sensor area, providing more space to place components on the PCB.



Reduce the noise:

Noise in the sensor raw count reduces the SNR and the proximity-sensing distance. To

attenuate the noise in the sensor output and improve the ESD performance, surround the proximity sensor with a
ground loop, as

Figure 10

shows. However, keep in mind that a ground loop around the sensor reduces the

proximity-sensing distance. The minimum recommended width for the ground loop is 1.5 mm, and the minimum
recommended clearance between the proximity sensor and the ground loop is 1 mm.

Figure 10. Ground Loop Surrounding the Proximity Sensor

PCB

Ground Loop

Proximity Sensor



Reduce sensor parasitic capacitance

The proximity-sensing distance depends on the ratio of the C

to the C

The proximity-sensing distance increases with an increase in the C

ratio. For a given sensor size, the value

of C

depends on the distance between the sensor and the target object. To maximize this ratio, you need to

increase C

and decrease C

. The C

of the sensor can be minimized by selecting an optimum sensor area,

reducing the sensor trace length, and minimizing the coupling of the sensor electric field lines to the ground.

To reduce the coupling of sensor electric field lines to the ground, drive the hatch pattern in the top and bottom
layer of the PCB (if there is any) with the driven shield signal. A hatch pattern that is connected to the driven
shield signal is called a

“shield electrode.” The driven shield signal is a replica of the sensor signal.

For shield electrode layout guidelines, refer to the

“Shield Electrode and Guard Sensor” section in the

Getting

Started with CapSense

design guide.

To minimize the sensor trace length and thereby the sensor C

, place the CapSense device as close as possible

to the sensor.



Eliminate the effect of floating or grounded conductive objects

The proximity-sensing distance is reduced

drastically if there is any nearby floating or grounded conductive object. You should either remove the nearby
conductive object or use a shield electrode to isolate the proximity sensor from the conductive object.

Note

Surrounding the sensor with a ground loop with a small trace width (1.5 mm) will not reduce the proximity-

sensing distance by a drastic amount.

For more details on the effect of floating or grounded conductive objects on the proximity-sensing distance, refer
to the

“Proximity Sensing” section in the

Getting Started with CapSense

design guide. For shield-electrode layout

guidelines, refer to the

“Shield Electrode and Guard Sensor” section in the

Getting Started with CapSense

design

guide.

In addition to these guidelines, you should also follow the layout best practices mentioned in the

“PCB Layout

Guidelines

” section in the

Getting Started with CapSense

design guide.

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Document No. 001-92239 Rev. *B

Tuning CapSense CSD Parameters for a Large Proximity-Sensing Distance

After you have completed the proximity sensor layout, the next step is to implement the firmware and tune the
CapSense CSD parameters for the proximity sensor to achieve an optimum performance.

Cypress’s

PSoC Creator

™

integrated design environment (IDE) provides a CapSense CSD Component to simplify CapSense system design.
See the

CapSense Component datasheet

The capacitance added by a target object at a distance from the proximity sensor is in tens of femtofarads, unlike
touching a button sensor, where the capacitance added is in hundreds of femtofarads. To detect a small change in
capacitance, the CapSense circuitry should be tuned for high sensitivity, and the threshold parameters should be set
to the optimum values. The process of setting CapSense CSD parameters for an optimum sensor performance is
called “tuning.” This section shows you how to tune the CapSense CSD parameters in the

PSoC Creator

IDE for a

proximity sensor to achieve optimum performance.

This section assumes that you are familiar with the PSoC 4 CapSense Component. If you are new to CapSense
design in PSoC 4, refer to the

CapSense Component datasheet

Figure 11

shows the high-level steps for tuning a proximity sensor implemented with a

PSoC 4

device. You can follow

the same procedure for tuning proximity sensors in other

CapSense devices

. Refer to the device-specific design

guides at

CapSense Design Guides

for tuning procedures.

Tuning a proximity sensor in PSoC Creator is similar to tuning a button sensor and can be performed in three high-
level steps:

Set Optimum CapSense CSD Parameters

Ensure SNR is Greater Than or Equal to 5:1

Set Optimum Threshold Parameters

7.1

Set Optimum CapSense CSD Parameters

1. Determine the sense clock divider and modulator clock divider values for the proximity sensor.

The sense clock divider determines the frequency of the precharge switch output, while the modulator clock
divider determines the CapSense

CSD modulator input frequency. Using Cypress’s SmartSense™ algorithm,

you can easily determine the sense clock divider and modulator clock divider values for a given sensor layout.
Refer to

Appendix A: Determining the Sense Clock Divider and Modulator Clock Divider Using SmartSense

for

details on how to set these parameters using the SmartSense algorithm.

2. Set the general properties of the CapSense Component.

In the PSoC Creator

TopDesign.cysch

window, double-click on the CapSense Component to configure the

CapSense CSD parameters. In the CapSense Component

General

configuration window, set the following

parameters to the values listed in

Table 3

3. Add a proximity sensor to your design.

Click the

Add proximity sensor

button in the CapSense Component

Widgets Config

window. Set the

resolution of each proximity sensor to 16 bits to achieve a large proximity-sensing distance. Leave the other
parameters unchanged. These parameters will be set in

Step 9

4. Set the advanced properties of the CapSense Component.

In the CapSense Component

Advanced

configuration window, set the parameters to the values listed in

Table 4.

Leave the other parameters unchanged. These parameters will be set in

Step 9

Refer to the

PSoC 4 CapSense Component datasheet

PSoC 4 CapSense Design Guide

for more details on

these parameters

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Document No. 001-92239 Rev. *B

Figure 11. Proximity Sensor Tuning Flow Chart

Start

Set CSD Tuning Parameters

Compute the SNR

Set Thresholds

SNR > 5:1?

Enable Firmware Filters

Scan Time Meets

Requirement?

SNR > 5:1?

Check the Layout for

Improvement. If Possible Increase

the Proximity Sensor Size

Decrease Resolution by

1-bit or Decrease

Modulation Divider

Yes

Configure the Device

and Compute SNR

SNR > 5:1?

Restore the Previous

Resolution or

Modulation Divider

End

Yes

Test and Retune

Table 3. CapSense Component General Configuration Window

Parameter

Value

Rationale

Tuning method

Manual with run-
time tuning

The manual method with the run-time tuning option allows you to change the tuning parameters
during run time.

Raw-data noise filter

None

Filters will be enabled in

Step 7

, depending on the SNR of the sensor.

Compensation IDAC

Enabled

Enabling the compensation IDAC selects the dual-IDAC mode operation of the CSD. Dual-IDAC
mode gives higher signal values compared to single-IDAC mode.

Auto-calibration

Checked

Enabling auto-calibration maintains the tuning by automatically calibrating the IDACs when the
sensor C

value varies from one PCB to another.

Waterproofing and
detection

Unchecked

This parameter should be enabled when your design has a guard sensor to eliminate sensor
false triggers due to liquid flow over the sensor.

Enable built-in self-
test

Unchecked

This parameter is not enabled because you are not using the C

measurement API to measure

the sensor C

value. You are using SmartSense to determine the sensor parameters.

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Document No. 001-92239 Rev. *B

Table 4. CapSense Component Advanced Configuration Window

Parameter

Value

Rationale

Current source

IDAC sourcing
(default)

The IDAC sourcing mode is recommended for most applications, as it is free from power supply
noise compared to the IDAC sinking mode.

IDAC range

The 4x range is sufficient for most applications. You can use the 8x range if C

is very high.

Analog switch drive
source

PRS-Auto

The pseudo random sequence (PRS) clock reduces the effects of external EMI on CapSense and
reduces sensor scan emissions.

Individual frequency
settings

Enabled

This option is enabled to specify the sense clock divider and modulator clock divider for each
sensor in the

Scan order

tab.

Sensor auto reset

Disabled
(default)

This option is set to

“Disabled” to ensure that the baseline is not always updated. Updating the

baseline may result in a reduced proximity-sensing distance when the target object approaches
the sensor very slowly.

Widget resolution

16-bit

Proximity sensors may have a difference count with a value greater than 255 (8-bit). Therefore, a
widget resolution of 16-bit is selected to ensure that the difference count is not truncated when it
is greater than 255. Set this value to 8-bit if you are expecting the difference count value to be
less than 255.

Shield

Enabled

This option allows you to drive the shield electrode with the driven shield signal.

Shield signal delay

None
(default)/OFF

For PSoC 4000 devices, set this parameter to

“OFF.” When the driven shield signal is not in

phase with the sensor signal, this parameter should be set to either

“10 ns” or “50 ns.”

For PSoC 4200 devices, set this parameter to

“None (default).” When the driven shield signal is

not in phase with the sensor signal, this parameter should be set to either

“1 cycle” or “2 cycle.”

Shield tank capacitor
enable

Enabled

It is recommended to use the shield-tank capacitor to reduce switching transients when the shield
electrode is charged and discharged.

Guard sensor

Disabled

The guard sensor should be enabled only when you need to eliminate false triggers due to liquid
flow over the sensor.

Inactive sensor
connection

Shield

Inactive sensors are connected to shield instead of ground because a nearby inactive sensor
creates grounding effects on the active proximity sensor and reduces the proximity-sensing
distance.

Shield tank capacitor
Precharge Settings

Precharge by IO
buffer

The precharge by IO buffer option is recommended for the Csh_tank capacitor because it can
quickly charge the capacitor.

7.2

Ensure SNR is Greater Than or Equal to 5:1

After the hardware parameters are set, you need to measure the sensor SNR and ensure that it is greater
than or equal to 5:1. An SNR of 5:1 ensures robust operation under all conditions.

SNR is the ratio of the sensor signal and the peak-to-peak noise counts, as shown in Equation 1.

SNR =

Equation 1

Where:

Signal = Raw count (with hand)

– raw count (without hand)

Peak-to-Peak Noise = Peak-to-peak noise of raw count measured over 3,000 samples, as shown in

Figure

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Document No. 001-92239 Rev. *B

Figure 12. Computing SNR

3460

3480

3500

3520

3540

3560

3580

3600

3620

3640

3660

200

400

600

800

1000

1200

1400

1600

Baseline

Raw

Cou

# Samples

3000

1500

4500

6000

1,550

1,500

1,600

1,650

1,700

Signal

Noise

oun

You can compute the SNR using two methods:



CapSense Tuner: Using the CapSense Tuner is the easiest method for computing the SNR. However,

this method supports only I

C communication to read the sensor data and requires you to run a specific

set of APIs in the firmware. See the

“Tuner GUI Interface”

section in the

PSoC 4 CapSense Component

datasheet.



Bridge Control Panel

(BCP): The BCP is a tool provided by Cypress to read data from a slave device

via an I

C/SPI/UART interface. For more details on how to use the BCP for reading data from a slave

device, refer to

AN2397

– CapSense Data Viewing Tools.

Appendix B: Reading Sensor Debug Data in

the Bridge Control Panel

shows you how to measure the SNR using the BCP tool.

Depending on your requirements, select a suitable method for measuring the SNR and implement the
firmware. The

Example Projects

provided with this application note implement both methods. You can use

that section as a reference and implement the method for computing the SNR. Steps

show you how to

achieve an SNR greater than 5:1.

5. Program the device with the settings shown in Steps

6. To compute the SNR, acquire 3,000 raw count samples, as

Figure 12

shows, and measure the peak-to-

peak noise count. Place your hand at the required proximity-sensing distance and measure the shift in
raw counts. The signal will be equal to the raw count (after placing the hand) minus the raw count
(before placing the hand.)

7. If the SNR computed in

Step 6

is greater than 5:1, proceed to

Step 8

; otherwise, enable the ALP filter

and measure the SNR.

Simple filters such as median, average, and infinite impulse response (IIR) may not be able to attenuate
the high noise in proximity sensors, so you need to use the ALP filter. The ALP filter is designed
specifically for attenuating noise in the proximity sensor and providing a fast response time.

If the SNR is not greater than 5:1 after enabling  the ALP filter, check for layout improvements such as
shielding  the  sensor  from  noise  sources  to  reduce  noise  or  increasing  the  sensor  loop  diameter  or
diagonal to increase the signal.

Restart from

Step 1

if you increase the sensor loop diameter or diagonal.

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Document No. 001-92239 Rev. *B

8. Once the SNR is greater than 5:1, check if the scan time and power consumption meet the

requirements.

If the scan time and power consumption meet the requirements, proceed to

Step 9

; otherwise, decrease

the sensor resolution or modulator clock divider and repeat from

Step 5

7.3

Set Optimum Threshold Parameters

9. If the SNR is greater than 5:1 and the scan time and power consumption requirements are met, set the

threshold parameters listed in

Table 5.

Table 5. Sensor Threshold Parameters

Threshold
Parameter

Tab Present

Recommended Value

Finger threshold

Widgets Config

80 percent of signal

Noise threshold

40 percent o

signal

Negative noise
threshold

Advanced

40 percent of signal

Hysteresis

Widgets Config

10 percent of signal

Debounce

Widgets Config

Set this parameter to ‘1’ if you
are using the ALP filter;
otherwise, set it to ‘3’

Low baseline reset

Advanced

Example Project 1

– Proximity Distance

follows this procedure and shows how to achieve a 10-cm proximity-

sensing distance with a square-loop proximity sensor whose diagonal length is 10.3 cm.

Firmware Filters for Reducing Noise

As explained previously, proximity sensors are susceptible to noise because of their large sensor area and
high-sensitivity setting. Filters help to reduce the noise in raw count and improve the SNR. A higher SNR
implies a large proximity-sensing distance.

The CapSense Component supports the following types of filters: median, average, and first-order IIR. Refer
to the

CapSense Component datasheet

for more details on these filters. The noise attenuation factor of

these filters depends on the order of the filter. The higher the filter order, the higher the noise attenuation will
be. However, higher order filters require more memory and result in a slower response.

To achieve high noise attenuation and improve the response time, you need to use intelligent adaptive filters
such as the ALP filter, as explained in the next section.

8.1

Advanced Low-Pass Filter

The ALP filter is a combination of multiple low-pass filters specifically designed to attenuate the noise in the
proximity sensor raw count.

Figure 13

shows the block diagram of the ALP filter. The ALP filter switches

between multiple low-pass filters depending on the sensor signal and values of the threshold parameters to
achieve the maximum noise attenuation and provide a fast response time.

The  ALP  filter  has  a  slow-response  filter  and  a  fast-response  filter.  The  slow-response  filter  provides  the
maximum  noise  attenuation,  but  its  response  time  is  slow.  On  the  other  hand,  the  fast-response  filter
provides a fast response time but results in less noise attenuation. By switching between these two filters,
the ALP filter provides the maximum noise attenuation and a fast response time.

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Document No. 001-92239 Rev. *B

Figure 13. ALP Filter Block Diagram

Average Filter

IIR filter

Decision Logic

K-Value

Proximity-Positive

Threshold

Proximity-Negative

Threshold

Raw Count

Average

Filtered Data

ALP Filtered

Data

ALP Filter

The inputs to the ALP filter are as follows:



Raw count:

The raw count of the sensor is the digital measurement of the capacitance of the sensor.



K-value:

The K-value of the ALP filter determines noise attenuation in the proximity sensor raw count.

The K-value can be one of the following:



IIR_K_16



IIR_K_32



IIR_K_64

Noise attenuation decreases in the following order:

IIR_K_64 > IIR_K_32 > IIR_K_16



Proximity-positive threshold:

This parameter determines the turn-on time of the proximity sensor

when a hand approaches it. When the sensor signal is greater than this value, the ALP filter switches to
the fast-response filter from the slow-response filter.



Proximity-negative threshold:

This parameter determines the turn-off time of the proximity sensor

when a hand is withdrawn from it. When the sensor signal is less than this value, the ALP filter switches
to the fast-response filter from the slow-response filter.

The outputs of the ALP filter are as follows:



Average filtered data:

Average filtered data is used to set the proximity-positive threshold and

proximity-negative threshold parameters.



ALP filtered data:

The ALP filtered data is the final output of the filter, that is, the raw count with very

low noise.

8 . 1 . 1

A d d i n g a n AL P F i l t e r t o t h e P r o j e c t

Refer to

Appendix D: Adding the ALP Filter Library to Any CapSense Project

for adding ALP filter to your

project.

Note:

The ALP filter requires all the proximity sensors to occupy a scan order 0 through (n-1) in the

CapSense

Component. Here, N is the total number of proximity sensors in the design. For proximity

sensors to occupy the scan order from 0, place the proximity sensor widget first followed by other sensor
widgets.

8 . 1 . 2

A L P F i l t e r T u n i n g

The ALP filter requires you to specify the K-value, proximity-positive threshold, and proximity-negative
threshold for proper operation. Follow these steps to set the ALP filter parameters.

1. Measure the peak-to-peak noise using the raw count without any nearby target object and filters.

2. Set the K-value per the mapping in

Table 6.

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Document No. 001-92239 Rev. *B

Table 6. Selecting the K-Value

Peak-to-Peak Noise

Recommended

K-Value

Less than 32 counts

IIR_K_16

Greater than 32 counts and less than 64
counts

IIR_K_32

Greater than 64 counts

IIR_K_64

3. Enable the ALP filter and program the device. Measure the peak-to-peak noise in the

ALP filter’s

average filtered data.

4. Set the proximity-positive threshold as equal to 1.5 × peak-to-peak noise of the average filtered data.

5. Set the proximity-negative threshold as equal to 0.5 × peak-to-peak noise of the average filtered data.

6. Set the finger threshold parameter as equal to the proximity-positive threshold. After tuning the ALP

filter, the finger threshold parameter should be set to the value listed in

Table 5.

7. Program the device with these settings and measure the peak-to-peak noise using the raw count for

3,000 samples.

8. Place your hand at the required proximity-sensing distance and measure the signal, that is, the shift in

the raw count when the hand approaches the sensor.

9. Compute the SNR. If the SNR is greater than 5:1, check if the sensor turn-off time is acceptable. If the

sensor turn-off time is very slow, increase the proximity-negative threshold value. The maximum limit for
the proximity-negative threshold parameter is equal to the proximity-positive threshold value.

10. If the SNR is greater than 5:1 and the sensor response time meets the requirements, proceed to set the

threshold parameters listed in

Table 5

; otherwise, check for layout improvements to minimize the noise

or increase the proximity sensor size to increase the signal.

Example Project 1

– Proximity Distance

shows how to use the ALP filter. The ALP filter is provided as a

library file. You can call the ALP filter APIs to apply the ALP filter on the sensor raw count. The ALP filter API
definitions are provided in

Appendix C: Advanced Low-Pass Filter API Definitions

Tuning for Liquid Tolerance

Water droplets or any other liquids may create false triggers when they fall on the proximity sensor. When a
liquid falls on the proximity sensor, it adds a capacitance and results in a signal (i.e. shift in raw count) that is
equal  to  the  signal  when  a  hand  is  placed  over  the  proximity  sensor  at  a  certain  distance  from  it.  To
eliminate  false  triggers  due  to  liquid  droplets,  Cypress  recommends  that  you  tune  the  CapSense  CSD
parameters in such a way that when a hand is placed over the proximity sensor (at the required proximity-
sensing  distance),  the  signal  is  at  least  three  times  greater  than  the  signal  due  to  liquid  droplets.  This
ensures that the sensor will operate reliably in all conditions throughout the life cycle.

Figure 14

shows the steps to tune a proximity sensor for liquid tolerance.

1. Connect the inactive sensor, hatch pattern, or any trace that is surrounding the proximity sensor to the

driven shield instead of connecting them to ground. This will minimize the signal due to the liquid
droplets when they fall on the sensor. The driven shield is a signal that replicates the sensor-switching
signal.

Refer to the “Shield Electrode and Guard Sensor” section in the

PSoC 4 CapSense Design

Guide

for details on how the driven shield works in a

PSoC 4

device.

2. Follow the tuning steps explained in the

Tuning CapSense CSD Parameters for a Large Proximity-

Sensing Distance

section to tune the CapSense CSD parameters to achieve an SNR greater than 5:1.

This step is to ensure that the SNR of the proximity sensor is greater than 5:1 without liquid droplets.

3. Place a liquid droplet (quantity depends on requirements) over the proximity sensor and measure the

signal, that is, the shift in the raw count when a liquid droplet falls on the sensor.

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Document No. 001-92239 Rev. *B

4. Bring your hand towards the sensor and find the distance at which the signal due to the hand is at least

three  times  greater  than  the  signal  due  to  the  liquid  droplet.  This  distance  is  the  maximum  possible
proximity-sensing  distance  that  can  be  achieved  with  liquid  tolerance  for  this  sensor  layout.  If  the
achieved  proximity-sensing  distance  meets  your  requirement,  proceed  to

Step

; otherwise, increase

the sensor loop diameter or diagonal to achieve the required proximity-sensing distance and restart
from

Step 1.

Note

There should not be any liquid droplets on the sensor while measuring the signal due to the hand.

5. To reduce the scan time and power consumption, reduce the resolution by one bit and check for the

following conditions:



SNR is greater than or equal to 5:1.



The signal due to the liquid droplet and the signal due to the hand at the new proximity-sensing

distance (measured in

Step

) meet the following requirement:

Signal (hand) > 3 * Signal (liquid droplet)

If these conditions are met, you can further reduce the resolution until one of the conditions fails. If
either of the conditions fails, restore the resolution to the previous value and continue with

Step

6. After the signal due to the hand is greater than three times the signal due to the liquid droplet, set the

threshold parameters to the values indicated in

Table 5. Example Project 2

– Liquid-Tolerant Proximity

shows you how to tune a proximity sensor for liquid tolerance.

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Document No. 001-92239 Rev. *B

Figure 14. Flow Chart for Tuning Proximity Sensor for Liquid Tolerance

Start

Drive Inactive Sensor and

Hatch Pattern with Driven

Shield

Tune Sensor For Maximum

Proximity Distance Without

Liquid Tolerance

Measure Signal Due to

Liquid Droplets

Measure the Proximity

Distance at Which Signal

(Hand) > 3 * Signal (Liquid)

Scan Time and Power
Optimization Required

Reduce Resolution by 1-Bit

Measure Signal (Liquid) and

Signal (Hand)

Signal (Hand) >

3 * Signal (Liquid) &

SNR > 5:1

Restore Resolution to

Previous Value

Set Thresholds

Yes

Stop

Proximity Distance

meets Requirements?

Increase Proximity Sensor

loop diameter

Yes

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Document No. 001-92239 Rev. *B

9.1

Implementing Gesture Detection with Proximity Sensors

Implementing gesture detection with a proximity sensor based on CapSense involves the following three
steps:

Sensor Design and Placement

Sensor Tuning

Firmware Design

9.2

Sensor Design and Placement

Proximity sensors detect gestures without any contact with the user. The proximity-sensing distance
depends on the sensor type and size. For detecting gestures at a long distance, you can use a PCB trace
(

Figure 15

) to implement a proximity sensor. Refer to the

“Proximity Sensing” section in the

Getting Started

with CapSense

design guide for guidelines on the type of sensor to select for a required proximity-sensing

distance.

Proximity sensor placement depends on the type of gesture that should be detected. For example, to detect
gestures such as horizontal swipes in the X-axis, you can use two proximity sensors, PS1 and PS2, which
are placed parallel to the horizontal hand movement in the X-axis, as

Figure 15

shows. Similarly, to detect

horizontal swipes in the Y-axis, you can place two proximity sensors, PS3 and PS4, parallel to the horizontal
hand movement in the Y-axis, as

Figure 15

shows.

9.3

Sensor Tuning

After the sensor layout is completed, sensor tuning plays an important role in achieving the required
proximity-sensing distance. Follow the steps explained in the

Tuning CapSense CSD Parameters for a

Large Proximity-Sensing Distance

section to tune the sensors to achieve the required proximity-sensing

distance.

9.4

Firmware Design

When an object is detected, the firmware algorithm interprets the sensor data and reports the gesture type.
There are various firmware techniques to detect gestures based on the sensor data (difference count and
sensor status).

A  simple  method  to  detect  gestures  is  to  compare  the  difference  count  or  sensor  status  of  the  proximity
sensors with respect to time. Each type of gesture will have a unique pattern in  the difference count or the
sensor status with respect to time. By detecting the difference count or sensor status pattern, you can easily
determine the type of gesture.

For example, when a left-to-right swipe is performed in the X-axis, the signal from the two proximity sensors,
PS1 and PS2, varies as

Figure 16

shows. The hand position can be determined by splitting the difference

counts of both the sensors into different regions as follows:



Region A: Sensor PS1 is ON and PS2 is OFF. The hand is close to sensor PS1 and farther from sensor
PS2.



Region B: Both PS1 and PS2 are ON. The hand is between PS1 and PS2.



Region C: PS2 is ON and PS1 is OFF. The hand is close to PS2 and farther from PS1.

When a left-to-right swipe is performed, PS1 will be triggered first, followed by PS2. You can determine this
trigger pattern to interpret the gesture. This method can also be applied to the sensor status of proximity
sensors PS3 and PS4 for detecting swipe gestures in the Y-axis.

Example Project 3

– Proximity Gestures

shows how to implement gesture detection using proximity sensors

based on CapSense.

Proximity Sensing with CapSense ®

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Document No. 001-92239 Rev. *B

Figure 15. Proximity Sensor Design and Placement for Gesture Detection

PS1

PS2

PS3

PS4

– Proximity Sensor

Figure 16.

Horizontal Gesture Detection

Time

Difference Count

– PS1

Difference Count

– PS2

Finger Threshold

Design Consideration to Achieve 30-cm Proximity-Sensing Distance

CapSense devices support a proximity-sensing distance of up to 30-cm under ideal conditions. The ideal
conditions required for achieving a 30-cm proximity sensing distance are:

a) There should not be any noise sources surrounding the sensor.

b) There are no grounded/floating metal objects within the vicinity of the proximity sensor.

The 30-cm proximity-sensing distance was achieved under ideal conditions using the following:



Sensor Design

: A wire loop of 17-cm diameter or a copper trace of 1.5-mm width and 17-cm diameter

was used as proximity sensor.



Sensor Tuning

: The tuning procedure mentioned in section

Tuning CapSense CSD Parameters for a

Large Proximity-Sensing Distance

was followed to tune CapSense CSD parameter.

Proximity Sensing with CapSense ®

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Document No. 001-92239 Rev. *B



ALP Filter Tuning

: To reduce the noise and provide a fast response time, the ALP filter was applied on

sensor raw counts. See

Firmware Filters for Reducing Noise

for details on using ALP filter.

Implementing Low-Power Systems Using the Wake-on-Approach

Low-power embedded design is motivated by the need to run applications for as long as possible while
consuming minimum power. In a battery-powered system, this need is magnified. Furthermore, low power
implies a lower cost of operation and a smaller battery size to make applications more mobile. When energy
comes at a premium as it does with today’s green initiatives, ensuring that an embedded system consumes
as little energy as possible is even important for wall-powered applications.

In an embedded system, to reduce power consumption, designers use low-power modes such as sleep and
deep-sleep. In an embedded system, the device performs its operation and enters a low-power mode. To
perform the operations required by the system, the device must wake up from the low-power mode.

Typical applications use one of the following methods:

1. Periodically wake up and perform the required operations and remain in the low-power mode for most of

the time. In this case, the system wakes up from low-power mode due to a periodic interrupt source.
One such source is a watchdog timer.

2. Remain in the low power mode unless an external event such as a GPIO interrupt is triggered or an I

address match needs attention.

These methods are conventional ways to achieve low  average power. Method 2 has lower average power
consumption compared to method 1 because  in method 2, the system is in low-power mode until the user
interacts with the system. However,  with method 2, the response of the  system is very slow. An intelligent
system  should  detect the  presence  of the user  before  the user interacts  with  the system  and  wake  up  the
system from a low-power mode. This method of waking the system from a low-power mode by detecting the
presence of a user is called

“wake-on-approach.”

The wake-on-approach feature uses proximity sensors to detect the presence of a user to wake the system.
This results in very low average power consumption and provides a quick response to user interactions.

This feature is useful in the following cases:

1. To reduce the power consumption of the entire system: In this case, the entire system except the

CapSense device can be put in sleep mode. The proximity sensor implemented with the CapSense
device detects the presence of a user and wakes the system up.

2. To reduce the average power consumption of the CapSense device: In this case, instead of scanning all

the CapSense sensors in the system, you can implement a proximity sensor and scan only the
proximity sensor. Alternatively, you can gang all the sensors and scan only the ganged sensor to check
for proximity. When proximity is detected, you can scan all the sensors and detect finger touches.

Method 1 is very easy to implement. You need to use the ON/OFF status of a proximity sensor to switch the
system between active mode and sleep mode. Method 2 is useful only in a few cases. This section shows
you when and how to implement method 2 to reduce the power consumption of a CapSense system.

In a CapSense system, the wake-on-approach feature is useful only when the total time taken to scan all the
sensors (excluding the time taken to scan the proximity sensors used for this feature) is greater than the
time taken to scan the proximity sensor, which will be used to implement it. The scan time of a sensor
depends on the sensor C

, CSD resolution, and modulator clock frequency.

Consider a CapSense application that has 10 CapSense buttons. Let the resolution of each sensor be 13-bit
and the modulator clock divider be

‘2’. As

Figure 17

shows, the time taken to scan each sensor is 1.365 ms,

and the total time taken to scan all 10 sensors is 13.652 ms.

Consider a CapSense system that has a proximity sensor surrounding all 10 button sensors. Let the
proximity sensor resolution be 16-bit and the modulator clock divider be

‘1’. As

Figure 18

shows, the time

taken to scan only the proximity sensor is 5.461 ms.

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Document No. 001-92239 Rev. *B

Figure 18. Estimating Proximity Sensor Scan Time

Implementing the Wake-on-Approach Using Sensor Ganging

You can implement a proximity sensor by ganging multiple button sensors or proximity sensors. Ganging
refers to simultaneously connecting multiple sensors to the CapSense circuitry and scanning them as a
single proximity sensor, as

Figure 19

shows

Ganging multiple sensors increases the effective sensor area

and results in a large proximity-sensing distance.

When a user is not interacting with the system, you can gang all the sensors in the system and scan them
as a single proximity sensor. When proximity is detected, the device can stop scanning the ganged sensor
and scan each sensor individually and detect finger touches. Sensor ganging reduces the total sensor scan
time and device power consumption.

The CapSense Component provides an easy method to implement sensor ganging. Consider a CapSense
system that has five button sensors. To gang these sensors, you add a proximity widget in the

Widgets

Config

tab in the CapSense Component configuration window. In the

Scan Order

tab, click on the proximity

sensor. A drop-down list will appear, as

Figure 20

shows. This drop-down list allows you to specify which

sensors in the system should be ganged and scanned as a single proximity sensor.

Refer to the application note

AN90114

– PSoC 4000 Family Low-Power System Design Techniques

for

details on how to implement a low-power CapSense system using sensor ganging.

Proximity Sensing with CapSense ®

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Document No. 001-92239 Rev. *B

Example Projects

This application note contains three example projects that demonstrate how to:



Tune proximity sensors for maximum proximity-sensing distance



Tune proximity sensors for liquid tolerance



Detect gestures using proximity sensors

The following are required for testing the example projects:



CY8CKIT-024 CapSense Proximity Shield Kit

: The CY8CKIT-024 is a shield that has proximity sensors

to evaluate the proximity-sensing performance of

Cypress’s PSoC CapSense devices. The CY8CKIT-

024 has Arduino

™-compatible headers and can be connected to

CY8CKIT-040 PSoC 4000 Pioneer

Development Kit

and

CY8CKIT-042 PSoC 4 Pioneer Kit



The

CY8CKIT-040

kit (with the PSoC 4000 part) or the

CY8CKIT-042

kit (with the PSoC 4200 part):

These kits connect to the

CY8CKIT-024

shield.



PSoC Creator software installed on your PC: The PSoC Creator IDE is required to view and edit these

example projects. You can download the latest version of PSoC Creator from the

PSoC Creator web

page



PSoC Programmer and the BCP: The PSoC Programmer software is used to program the PSoC

devices on the

CY8CKIT-040

kit and

CY8CKIT-042

kit with the hex files. The BCP software is used to

view the CapSense sensor data such as raw count, baseline, and difference count. The BCP software
is installed along with PSoC Programmer. You can download PSoC Programmer at

www.cypress.com/go/psocprogrammer

Two sets of example projects are provided to operate on CY8CKIT-024 with the PSoC Pioneer Kits
CY8CKIT-040 and CY8CKIT-042. The example projects are available at

AN92239

on Cypress’s website.

To open an example project in PSoC Creator, navigate to the folder where you have extracted the example
project and double-click on the <

Project.cywrk

13.1

Example Project 1

– Proximity Distance

The Proximity_Distance_040 project is designed to operate on CY8CKIT-040 with CY8CKIT-024, while the
Proximity_Distance_042 project is designed to operate on CY8CKIT-042 with CY8CKIT-024. These two
projects demonstrate how to tune the PROX proximity sensor (square loop with a diagonal length of 10.3
cm) on CY8CKIT-024 to achieve a proximity-sensing distance of 10 cm. The example projects show how to
set optimum CapSense CSD parameters for a proximity sensor and apply an

Advanced Low-Pass Filter

achieve a proximity-sensing distance of 10 cm.

The proximity of the user is indicated by driving the LEDs (LED1

–LED5) with a PWM signal. The LEDs glow

at minimum brightness when the hand is at a 10-cm proximity-sensing distance, and the brightness
increases as the hand approaches the sensor.

1 3 . 1 . 1 P r o j e c t D e t a i l s

The behavior of the project is described in a flow chart in

Figure 21

. The procedure explained in the

Tuning

CapSense CSD Parameters for a Large Proximity-Sensing Distance

section was followed to tune the

CapSense CSD parameters for the PROX sensor.

The Proximity_Distance_04x projects use only the PROX sensor. The PS1, PS2, PS3, and PS4 sensors are
not scanned in the firmware and are always connected to ground to reduce noise in the proximity sensor raw
count. The GND/SHIELD loop is connected to the shield pin of the PSoC 4 device. As the

Eliminate the

effect of floating or grounded conductive objects

list item explains, driving a nearby conductive object

(GND/SHIELD loop) with the driven shield signal eliminates the effect of these conductive objects on the
proximity-sensing distance and provides a large proximity-sensing distance.

The following steps show how the CapSense CSD parameters were tuned to achieve a 10-cm proximity-
sensing distance with CY8CKIT-040.

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Document No. 001-92239 Rev. *B

Figure 21. Proximity Distance Project Flow Chart

Start

Enable Global Interrupt

Set ALP Filter

Thresholds

Initialize CapSense

Scan Proximity Sensor

Update Proximity

Sensor Baseline

Control LED Brightness

Apply ALP filter on Raw

Counts

Enable Proximity

Sensor

Initialize ALP Filter

History, Set ALP K-

Value

Tuner

Enabled ?

Run Tuner

Yes

Start Timer to Generate

Software PWM

TX8 Enabled?

Send Sensor Data Via

TX8

Yes

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Document No. 001-92239 Rev. *B

1. In the CapSense CSD Component, the tuning method is selected as SmartSense to determine the

sense clock divider and modulator clock divider value for the PROX sensor.

2. Shield is enabled in the

Advanced

tab to drive the, hatch pattern in the bottom layer and the

GND/SHIELD loop on

CY8CKIT-024

with the driven shield signal. The driven shield signal reduces the

effect of floating conductive objects on the PROX sensor proximity-sensing distance and helps in
achieving a large proximity-sensing distance.

3. Tuner is enabled to read the sense clock divider and modulator clock divider values. The sense clock

divider is

set to ‘2’, and the modulator clock divider is set to ‘1’.

4. In the CapSense Component

General

configuration window, the parameters are set to the values

shown

Table 3

5. In the

Widgets Config

section, the resolution for the PROX sensor is set to 16 bits. All other settings

retain their default values.

6. TX8 communication (Software Transmit UART) is established with the PSoC 4000 device on CY8CKIT-

040 to view the sensor data such as the raw count, baseline, and difference count to measure the SNR.
Refer to

Appendix B: Reading Sensor Debug Data in the Bridge Control Panel

for details on how to

view sensor debug data via UART in the

BCP

tool.

7. Using this configuration, the SNR for the proximity sensor PROX is measured. The noise is measured

to  be  approximately  100  counts.  The  signal  at  a  10-cm  proximity-sensing  distance  is  measured  to  be
approximately  220.  Therefore,  the  SNR  =  220/100  =  2.2.  Because  the  SNR  is  less  than  5:1,  the  ALP
filter is enabled to attenuate the noise and increase the SNR.

8. The ALP filter parameters are tuned as explained in the

ALP Filter Tuning

section. With the ALP filter,

the noise is measured to be approximately 10 counts and the SNR at a 10-cm distance is 220/10 =22:1.

To achieve an SNR of 5:1 with a noise count of 10, the signal should be 50. Therefore, the threshold
parameters are set to the values listed in

Table 5

, assuming a signal of 50. With a finger-threshold value

of 40, a proximity-sensing distance of 12 cm is achieved.

1 3 . 1 . 2 H a r d w a r e C o n f i g u r a t i o n

To test the project with CY8CKIT-040, remove jumper J14 and connect the kit to CY8CKIT-024, as

Figure

shows. When the two kits are connected, the J1, J2, J3, and J4 headers on CY8CKIT-040 connect to the

J1, J2, J3, and J4 headers on CY8CKIT-024 respectively.

Similarly, to test the project with CY8CKIT-042, connect the kit to CY8CKIT-024, as

Figure 23

shows.

When the two kits are connected, the J1, J2, J3, and J4 headers on CY8CKIT-042 connect to the J1, J2, J3,
and J4 headers on CY8CKIT-024 respectively. If you want to read the proximity sensor data via UART,
connect a jumper wire between pin P0[1] on the J2 header and P12[6] on the J8 header using a wire, as

Figure 24

shows.

On CY8CKIT-024, slide SW1 to select SHIELD to drive the GND/SHIELD loop and the bottom hatch pattern
with the driven shield signal.

Table 7

lists the pin connections for the example projects.

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Document No. 001-92239 Rev. *B

Table 7. Pin Connections for Proximity_Distance_040 Project and Proximity_Distance_042 Project

Pin Name in Project

Pin Name on CY8CKIT-024

Pin Number

CY8CKIT-040

CY8CKIT-042

PROX_0_PROX

PROX

P0[3]

P0[0]

PS1_BTN

PS1

P1[7]

P0[6]

PS2_BTN

PS2

P0[5]

P0[4]

PS3_BTN

PS3

P0[1]

P2[1]

PS4_BTN

PS4

P1[0]

Cmod

–

P0[4]

P4[2]

Shield

SHIELD

P0[6]

P0[5]

Cshield_tank

–

P0[2]

P4[3]

LED1

P1[5]

P3[6]

LED2

P1[4]

P2[6]

LED3

P0[7]

LED4

P2[0]

P2[7]

LED5

P0[0]

P2[0]

EzI2C:SCL

–

P1[2]

P3[0]

EzI2C:SDA

–

P1[3]

P3[1]

Tx8

–

P3[0]

P0[1]

1 3 . 1 . 3 T e s t i n g t h e P r o x i m i t y_ D i s t a n c e P r o j e c t

To test the project on CY8CKIT-040, program the PSoC 4000 device with the

Proximity_Distance_040.hex

file. Similarly, to test the project on CY8CKIT-042, program the PSoC 4200 device with the

Proximity

_Distance_042.hex

file

For details on programming the PSoC 4000 and PSoC 4200 devices, refer to the

CY8CKIT-040 User Guide

and

CY8CKIT-042 User Guide

respectively.

Note the following:



Connect CY8CKIT-024 to CY8CKIT-040/ CY8CKIT-042 before programming.



Press the reset switch, SW1, on CY8CKIT-040/CY8CKIT-042 whenever you change the slide switch,

SW1, position on CY8CKIT-024 or when you place a ruler near the kit to measure the proximity-sensing
distance, as

Figure 25

shows.

To measure the proximity-sensing distance, hover your hand over the kit at approximately 10 cm, as

Figure

shows

The LEDs (LED1

–LED5) glow at their minimum brightness, showing that proximity is detected.

Bring your hand towards the kit and verify that the LED brightness increases, indicating closer proximity of
the hand with respect to the proximity sensor.

Note

When UART (software TX8) communication is enabled in the project for reading the CapSense sensor

data, the LEDs flicker. This is because the software TX8 disables the global interrupt during data
transmission. When the global interrupt is disabled, the timer ISR will not be serviced and the PWM
frequency varies, resulting in LED flickering.

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Document No. 001-92239 Rev. *B

Figure 25. Measuring Proximity-Sensing Distance

10 cm

13.2

Example Project 2

– Liquid-Tolerant Proximity

The Liquid_Tolerant_Proximity_040 project is designed to operate on CY8CKIT-040 with CY8CKIT-024, and
the Liquid_Tolerant_Proximity_042

project

is designed to operate on CY8CKIT-042 with CY8CKIT-024.

These two projects demonstrate how to tune the proximity sensor, PROX, on CY8CKIT-024 for liquid
tolerance. The project is tuned for a proximity-sensing distance of 3 cm with liquid tolerance. The proximity
of the user hand is indicated by turning on the LEDs (LED1

–LED5).

1 3 . 2 . 1 P r o j e c t D e t a i l s

The  Liquid_Tolerant_Proximity_04x  projects  use  only  the  PROX  sensor.  PS1,  PS2,  PS3,  and  PS4  are not
scanned in the firmware and are always  connected to the driven shield signal along with the GND/SHIELD
loop.  As  explained  in  the

Eliminate the effect of floating or grounded conductive objects

list item, driving

nearby sensors or PCB traces (GND/SHIELD loop, hatch pattern in the bottom layer) with the driven shield
signal helps in reducing the signal (i.e. shift in raw count) due to liquid droplets.

The proximity sensor, PROX, is tuned by following the steps mentioned in the

Tuning for Liquid Tolerance

section. The following steps show how the sensor was tuned for liquid tolerance with CY8CKIT-040.

1. The resolution of the PROX sensor is set to 16 bits, and a water droplet is poured over the PROX

sensor. The signal due to the water droplet is noted.

2. A hand is brought towards the proximity sensor, and it is found that at a 3-cm distance from the sensor,

the signal due to the hand is three times the signal due to the water droplet. Therefore, for the present
sensor layout, the maximum proximity-sensing distance that can be achieved with water tolerance is 3
cm.

3. To optimize the scan time and power consumption, the resolution is decreased by one bit and the SNR

is measured at 3 cm. It is found that with a resolution of 13 bits, a proximity-sensing distance of 3 cm
can be achieved with an SNR greater than 5:1.

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Document No. 001-92239 Rev. *B

1 3 . 2 . 2 H a r d w a r e C o n f i g u r a t i o n

To test the project, follow the steps explained in the

Hardware Configuration

section in

Page 28

Table 8

lists

the pin mapping for Liquid_Tolerant_04x projects.

Table 8. Pin Connections for Liquid_Tolerant_Proximity_040 and Liquid_Tolerant_Proximity_042 Projects

Pin Name in

Project

Pin Name on

CY8CKIT-024

Pin Number

CY8CKIT-040

CY8CKIT-042

PROX_0_PROX

PROX

P0[3]

P0[0]

PS1_BTN

PS1

P1[7]

P0[6]

PS2_BTN

PS2

P0[5]

P0[4]

PS3_BTN

PS3

P0[1]

P2[1]

PS4_BTN

PS4

P1[0]

Cmod

–

P0[4]

P4[2]

Shield

SHIELD

P0[6]

P0[5]

Cshield_tank

–

P0[2]

P4[3]

LED1

P1[5]

P3[6]

LED2

P1[4]

P2[6]

LED3

P0[7]

LED4

P2[0]

P2[7]

LED5

P0[0]

P2[0]

EzI2C:SCL

–

P1[2]

P3[0]

EzI2C:SDA

–

P1[3]

P3[1]

Tx8

–

P3[0]

P0[1]

1 3 . 2 . 3 T e s t i n g t h e L i q u i d _ T o l e r a n t _ P r o x i m i t y P r o j e c t

test

the

project

CY8CKIT-040,

program

the

PSoC

4000

device

with

the

Liquid_Tolerant_Proximity_040.hex

file. Similarly, to test the project on CY8CKIT-042, program the PSoC

4200 device with the

Liquid_Tolerant_Proximity_042.hex

file

For details on programming the PSoC 4000 and PSoC 4200 devices, refer to the

CY8CKIT-040 User Guide

and

CY8CKIT-042 User Guide

respectively.

Note the following:



Connect CY8CKIT-024 to CY8CKIT-040/CY8CKIT-042 before programming.



Press the reset switch, SW1, on CY8CKIT-040/CY8CKIT-042 whenever you change the slide switch,

SW1, position on CY8CKIT-024 or when you place a ruler near the kit to measure the proximity-sensing
distance, as

Figure 25

shows.

To place the water droplets on the proximity sensor (as

Figure 26

shows), use the liquid dropper

provided with CY8CKIT-024. After placing the water droplet, verify that the LEDs (LED1

–LED5) do not

turn on when water droplets are present on the sensor. Hover your hand over the kit at a distance of 3
cm, as

Figure 27

shows, and verify that the LEDs (LED1

–LED5) are turned ON to indicate proximity

detection.

Note:

When placing the water droplet, if the hand is within proximity-sensing distance (3 cm), proximity

will be detected and the LEDs will be turned ON. The LEDs will be turned off when you remove your
hand after placing the water droplet, indicating that the water droplet is not causing false triggers.

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Document No. 001-92239 Rev. *B

Figure 26. Placing Water Droplet over Proximity Sensor

Water Droplet

Figure 27. Proximity Detection in Presence of Water Droplet

Water Droplet

13.3

Example Project 3

– Proximity Gestures

The project Proximity_Gestures_040 is designed to operate on CY8CKIT-040 with CY8CKIT-024, and the
project Proximity_Gestures_042 project is designed to operate on CY8CKIT-042 with CY8CKIT-024. The
projects demonstrate how to detect swipe gestures in the X-axis and Y-axis using the proximity sensors on

CY8CKIT-024

The Proximity_Gestures_04x projects use only the PS1, PS2, PS3, and PS4 proximity sensors, as

Figure 28

shows. The PROX sensor is not scanned in the firmware and is always connected to the driven shield along
with the GND/SHIELD loop. A nearby floating or grounded conductive object reduces the proximity-sensing
distance of the active proximity sensors. As explained in the

Eliminate the effect of floating or grounded

conductive objects

list item, driving nearby sensors and PCB traces with the driven shield signal reduces the

effect of floating or grounded conductive objects on the proximity-sensing distance of the active sensors.
The proximity sensors PS1, PS2, PS3, and PS4 on CY8CKIT-024 are used to detect swipe gestures in the
X-axis and Y-axis. PS1 and PS2 are used for detecting swipe gestures in the X-axis, while PS3 and PS4 are
used for detecting swipe gestures in the Y-axis.

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Document No. 001-92239 Rev. *B

Figure 28. Sensor Placement in CY8CKIT-024

The projects contain two macros, GESTURE_AXIS and LED_DRIVE_SEQUENCE, in the

gestures.h

file.

These macros are used to select the type of gesture to be detected and the LED drive sequence
respectively.



GESTURE_AXIS:

This macro determines the type of gesture detected by the device. Set this macro to

“XAXIS” to detect swipe gestures in the X-axis, and set it to “YAXIS” to detect swipe gestures in the
Y-axis. By default, the macro is set to

“XAXIS” to detect swipe gestures in the X-axis.



LED_DRIVE_SEQUENCE:

This macro determines how the LEDs are driven when a gesture is

detected. Set this macro to

“LED_DRIVE_DURING_GESTURE” to drive the LEDs based on the current

position of the hand, and set it to

“LED_DRIVE_AFTER_GESTURE” to drive the LEDs after a gesture is

detected. By default, the macro is set to

“LED_DRIVE_DURING_GESTURE.”

When the macro is set to “LED_DRIVE_DURING_GESTURE,” the LEDs (LED1–LED5) are driven as
listed in

Table 9

When the macro is set to

“LED_DRIVE_AFTER_GESTURE,” the LEDs (LED1–LED5)

are driven as listed in

Table 10

Table 9. LED Turn-ON Sequence for LED_DRIVE_DURING_GESTURE

Gesture

Direction

LED Activated

Horizontal Swipe

Left

LED1

Middle

LED2

Right

LED3

Vertical Swipe

Bottom

LED5

Middle

LED2

Top

LED4

Table 10. LED Turn-ON Sequence for LED_DRIVE_AFTER_GESTURE

Gesture

Gesture Direction

LED Sequence

Horizontal
Swipe

Left to right

LED1



LED2



LED3

Right to left

LED3



LED2



LED1

Vertical

Top to bottom

LED4



LED2



LED5

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Document No. 001-92239 Rev. *B

Swipe

Bottom to top

LED5



LED2



LED4

1 3 . 3 . 1 P r o j e c t D e t a i l s

The behavior of the project is described in the flow chart in

Figure 29

. In Proximity_Gestures_04x projects,

the status of sensors PS1 and PS2 is compared to determine the swipe gesture in the X-axis, and the status
of sensors PS3 and PS4 is compared to determine the swipe gesture in the Y-axis. The sensor status is
tracked with respect to the time to determine the type of gesture performed. When the gesture is detected,
the LEDs are turned ON in a sequence based on the gesture type and LED drive type, as listed in

Table 9

and

Table 10

1 3 . 3 . 2 H a r d w a r e C o n f i g u r a t i o n

To test the project, follow the steps explained in the

Hardware Configuration

section.

Table 11

lists the

connections for Proximity_Gestures_04x

projects.

Figure 29. Proximity Gestures Project Flow Chart

Start

Enable Global Interrupt and

Initialize Gesture Variables

Enable All Proximity Sensors

Initialize CapSense

Component

Scan All Proximity Sensors

Update Baselines of All

Sensors

Detect Gestures and Drive

LEDs

Tuner

Enabled ?

Run Tuner

TX8 Enabled?

Send Sensor Data Via

TX8

Yes

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Document No. 001-92239 Rev. *B

Table 11. Pin Connections for Proximity_Gestures_040 and Proximity_Gestures_042 Projects

Pin Name in Project

Pin Name on CY8CKIT-024

Pin Number

CY8CKIT-040

CY8CKIT-042

PS1_0_PROX

PS1

P1[7]

P0[6]

PS2_0_PROX

PS2

P0[5]

P0[4]

PS3_0_PROX

PS3

P0[1]

P2[1]

PS4_0_PROX

PS4

P1[0]

PROX_0_PROX

PROX

P0[3]

P0[0]

Cmod

–

P0[4]

P4[2]

Shield

SHIELD

P0[6]

P0[5]

Cshield_tank

–

P0[2]

P4[3]

LED1

P1[5]

P3[6]

LED2

P1[4]

P2[6]

LED3

P0[7]

LED4

P2[0]

P2[7]

LED5

P0[0]

P2[0]

EzI2C:SCL

–

P1[2]

P3[0]

EzI2C:SDA

–

P1[3]

P3[1]

Tx8

–

P3[0]

P0[1]

1 3 . 3 . 3 T e s t i n g t h e P r o x i m i t y_ G e s t u r e s P r o j e c t

To test the project on CY8CKIT-040, program the PSoC 4000 device with the

Proximity_Gestures_040.hex

file. Similarly, to test the project on CY8CKIT-042, program the PSoC 4200 device with the

Proximity_Gestures_042.hex

file

For details on programming the PSoC 4000 and PSoC 4200 devices, refer to the

CY8CKIT-040 User Guide

and

CY8CKIT-042 User Guide

respectively.

Note the following:



Connect CY8CKIT-024 to CY8CKIT-040/CY8CKIT-042 before programming.



Press the reset switch, SW1, on CY8CKIT-040/CY8CKIT-042 whenever you change the slide switch,

SW1, position on CY8CKIT-024.

To verify the swipe gesture performed in the X-axis, hover your hand over the kit at a distance of 2 cm and
move the hand from left to right, as

Figure 30

shows, or from right to left. Observe that the LEDs turn on in

the sequence listed in

Table 9.

Similarly, to verify the swipe gestures performed in the Y-axis, set the macro GESTURE_AXIS to

“YAXIS”

and program the device. Hover your hand over the kit at a distance of 2 cm and move it from top to bottom,
as

Figure 31

shows, or from bottom to top. Observe that the LEDs turn on in the sequence listed in

Table 9

To drive the LEDs after the gesture is completed, set the macro LED_DRIVE_SEQUENCE to
“LED_DRIVE_AFTER_GESTURE” and repeat this procedure using

Table 10

as a guide.

Note:

When the macro LED_DRIVE_SEQUENCE is set to

“LED_DRIVE_AFTER_GESTURE,” the LEDs will

be turned ON only when the gesture is completed, that is, when the hand has completely moved away from
the kit.

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Document No. 001-92239 Rev. *B

Glossary

AMUXBUS

Analog multiplexer bus available inside PSoC that helps to connect I/O pins with multiple internal analog
signals.

SmartSense™ Auto-Tuning

A CapSense algorithm that automatically sets sensing parameters for optimal performance after the design
phase and continuously compensates for system, manufacturing, and environmental changes.

Baseline

A value resulting from a firmware algorithm that estimates a trend in the Raw Count when there is no human
finger present on the sensor. The Baseline is less sensitive to sudden changes in the Raw Count and
provides a reference point for computing the Difference Count.

Button or Button Widget

A widget with an associated sensor that can report the active or inactive state (that is, only two states) of the
sensor. For example, it can detect the touch or no-touch state of a finger on the sensor.

Difference Count

The difference between Raw Count and Baseline. If the difference is negative, or if it is below Noise
Threshold, the Difference Count is always set to zero.

Capacitive Sensor

A conductor and substrate, such as a copper button on a printed circuit board (PCB), which reacts to a touch
or an approaching object with a change in capacitance.

CapSense

Cypress’s touch-sensing user interface solution. The industry’s No. 1 solution in sales by 4x over No. 2.

CapSense Mechanical Button Replacement (MBR)

Cypress’s configurable solution to upgrade mechanical buttons to capacitive buttons, requires minimal
engineering effort to configure the sensor parameters and does not require firmware development. These
devices include the CY8CMBR3XXX and CY8CMBR2XXX families.

Centroid or Centroid Position

A number indicating the finger position on a slider within the range given by the Slider Resolution. This
number is calculated by the CapSense centroid calculation algorithm.

Compensation IDAC

A programmable constant current source, which is used by CSD to compensate for excess sensor C

. This

IDAC is not controlled by the Sigma-Delta Modulator in the CSD block unlike the Modulation IDAC.

CSD

CapSense Sigma Delta (CSD) is a Cypress-patented method of performing self-capacitance (also called
self-cap) measurements for capacitive sensing applications.

In CSD mode, the sensing system measures the self-capacitance of an electrode, and a change in the self-
capacitance is detected to identify the presence or absence of a finger.

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Debounce

A parameter that defines the number of consecutive scan samples for which the touch should be present for
it to become valid. This parameter helps to reject spurious touch signals.

A finger touch is reported only if the Difference Count is greater than Finger Threshold + Hysteresis for a
consecutive Debounce number of scan samples.

Driven-Shield

A technique used by CSD for enabling liquid tolerance in which the Shield Electrode is driven by a signal
that is equal to the sensor switching signal in phase and amplitude.

Electrode

A conductive material such as a pad or a layer on PCB, ITO, or FPCB. The electrode is connected to a port
pin on a CapSense device and is used as a CapSense sensor or to drive specific signals associated with
CapSense functionality.

Finger Threshold

A parameter used with Hysteresis to determine the state of the sensor. Sensor state is reported ON if the
Difference Count is higher than Finger Threshold + Hysteresis, and it is reported OFF if the Difference Count
is below Finger Threshold

– Hysteresis.

Ganged Sensors

The method of connecting multiple sensors together and scanning them as a single sensor. Used for
increasing the sensor area for proximity sensing and to reduce power consumption.

To  reduce  power  when  the  system  is  in  low-power  mode,  all  the  sensors  can  be  ganged  together  and
scanned as a single sensor taking less time instead of scanning all the sensors individually. When the user
touches  any  of  the  sensors,  the  system  can  transition  into  active  mode  where  it  scans  all  the  sensors
individually to detect which sensor is activated.

PSoC supports sensor-ganging in firmware, that is, multiple sensors can be connected simultaneously to
AMUXBUS for scanning.

Gesture

Gesture is an action, such as swiping and pinch-zoom, performed by the user. CapSense has a gesture
detection feature that identifies the different gestures based on predefined touch patterns. In the CapSense
component, the Gesture feature is supported only by the Touchpad Widget.

Guard Sensor

Copper trace that surrounds all the sensors on the PCB, similar to a button sensor and is used to detect a
liquid stream. When the Guard Sensor is triggered, firmware can disable scanning of all other sensors to
prevent false touches.

Hatch Fill or Hatch Ground or Hatched Ground

While designing a PCB for capacitive sensing, a grounded copper plane should be placed surrounding the
sensors for good noise immunity. But a solid ground increases the parasitic capacitance of the sensor which
is not desired. Therefore, the ground should be filled in a special hatch pattern. A hatch pattern has closely-
placed, crisscrossed lines looking like a mesh and the line width and the spacing between two lines
determine the fill percentage. In case of liquid tolerance, this hatch fill referred as a shield electrode is driven
with a shield signal instead of ground.

Hysteresis

A parameter used to prevent the sensor status output from random toggling due to system noise, used in
conjunction with the Finger Threshold to determine the sensor state. See

Finger Threshold

IDAC (Current-Output Digital-to-Analog Converter)

Programmable constant current source available inside PSoC, used for CapSense and ADC operations.

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Liquid Tolerance

The ability of a capacitive sensing system to work reliably in the presence of liquid droplets, streaming
liquids or mist.

Linear Slider

A widget consisting of more than one sensor arranged in a specific linear fashion to detect the physical
position (in single axis) of a finger.

Low Baseline Reset

A parameter that represents the maximum number of scan samples where the Raw Count is abnormally
below the Negative Noise Threshold. If the Low Baseline Reset value is exceeded, the Baseline is reset to
the current Raw Count.

Manual-Tuning

The manual process of setting (or tuning) the CapSense parameters.

Matrix Buttons

A widget consisting of more than two sensors arranged in a matrix fashion, used to detect the presence or
absence of a human finger (a touch) on the intersections of vertically and horizontally arranged sensors.

If M is the number of sensors on the horizontal axis and N is the number of sensors on the vertical axis, the
Matrix Buttons Widget can monitor a total of M x N intersections using ONLY M + N port pins.

When using the CSD sensing method (self-capacitance), this Widget can detect a valid touch on only one
intersection position at a time.

Modulation Capacitor (CMOD)

An external capacitor required for the operation of a CSD block in Self-Capacitance sensing mode.

Modulator Clock

A clock source that is used to sample the modulator output from a CSD block during a sensor scan. This
clock is also fed to the Raw Count counter. The scan time (excluding pre and post processing times) is given
by
(2

– 1)/Modulator Clock Frequency, where N is the Scan Resolution.

Modulation IDAC

Modulation IDAC is a programmable constant current source, whose output is controlled (ON/OFF) by the
sigma-delta modulator output in a CSD block to maintain the AMUXBUS voltage at V

REF

. The average

current supplied by this IDAC is equal to the average current drawn out by the sensor capacitor.

Mutual-Capacitance

Capacitance associated with an electrode (say TX) with respect to another electrode (say RX) is known as
mutual capacitance.

Negative Noise Threshold

A threshold used to differentiate usual noise from the spurious signals appearing in negative direction. This
parameter is used in conjunction with the Low Baseline Reset parameter.

Baseline is updated to track the change in the Raw Count as long as the Raw Count stays within Negative
Noise Threshold, that is, the difference between Baseline and Raw count (Baseline

– Raw count) is less

than Negative Noise Threshold.

Scenarios that may trigger such spurious signals in a negative direction include: a finger on the sensor on
power-up, removal of a metal object placed near the sensor, removing a liquid-tolerant CapSense-enabled
product from the water; and other sudden environmental changes.

Noise (CapSense Noise)

The variation in the Raw Count when a sensor is in the OFF state (no touch), measured as peak-to-peak
counts.

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Noise Threshold

A parameter used to differentiate signal from noise for a sensor. If Raw Count

– Baseline is greater than

Noise Threshold, it indicates a likely valid signal. If the difference is less than Noise Threshold, Raw Count
contains nothing but noise.

Overlay

A non-conductive material, such as plastic and glass, which covers the capacitive sensors and acts as a
touch-surface. The PCB with the sensors is directly placed under the overlay or is connected through
springs. The casing for a product often becomes the overlay.

Parasitic Capacitance (C

)

Parasitic capacitance is the intrinsic capacitance of the sensor electrode contributed by PCB trace, sensor
pad, vias, and air gap. It is unwanted because it reduces the sensitivity of CSD.

Proximity Sensor

A sensor that can detect the presence of nearby objects without any physical contact.

Radial Slider

A widget consisting of more than one sensor arranged in a specific circular fashion to detect the physical
position of a finger.

Raw Count

The unprocessed digital count output of the CapSense hardware block that represents the physical
capacitance of the sensor.

Refresh Interval

The time between two consecutive scans of a sensor.

Scan Resolution

Resolution (in bits) of the Raw Count produced by the CSD block.

Scan Time

Time taken for completing the scan of a sensor.

Self-Capacitance

The capacitance associated with an electrode with respect to circuit ground.

Sensitivity

The change in Raw Count corresponding to the change in sensor capacitance, expressed in counts/pF.
Sensitivity of a sensor is dependent on the board layout, overlay properties, sensing method, and tuning
parameters.

Sense Clock

A clock source used to implement a switched-capacitor front-end for the CSD sensing method.

Sensor

See

Capacitive Sensor

Sensor Auto Reset

A setting to prevent a sensor from reporting false touch status indefinitely due to system failure, or when a
metal object is continuously present near the sensor.

When Sensor Auto Reset is enabled, the Baseline is always updated even if the Difference Count is greater
than the Noise Threshold. This prevents the sensor from reporting the ON status for an indefinite period of
time. When Sensor Auto Reset is disabled, the Baseline is updated only when the Difference Count is less
than the Noise Threshold.

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Sensor Ganging

See

Ganged Sensors

Shield Electrode

Copper fill around sensors to prevent false touches due to the presence of water or other liquids. Shield
Electrode is driven by the shield signal output from the CSD block. See

Driven-Shield

Shield Tank Capacitor (C

)

An optional external capacitor (C

Tank Capacitor) used to enhance the drive capability of the CSD shield,

when there is a large shield layer with high parasitic capacitance.

Signal (CapSense Signal)

Difference Count is also called Signal. See Difference Count.

Signal-to-Noise Ratio (SNR)

The ratio of the sensor signal, when touched, to the noise signal of an untouched sensor.

Slider Resolution

A parameter indicating the total number of finger positions to be resolved on a slider.

Touchpad

A Widget consisting of multiple sensors arranged in a specific horizontal and vertical fashion to detect the X
and Y position of a touch.

Trackpad

See

Touchpad

Tuning

The process of finding the optimum values for various hardware and software or threshold parameters
required for CapSense operation.

REF

Programmable reference voltage block available inside PSoC used for CapSense and ADC operation.

Widget

A user-interface element in the CapSense component that consists of one sensor or a group of similar
sensors. Button, proximity sensor, linear slider, radial slider, matrix buttons, and touchpad are the supported
widgets.

Summary

This application note explained how to design a proximity sensor and tune the CapSense CSD parameters for a large
proximity-sensing distance and liquid tolerance. It also provided details on how to implement gesture detection based
on proximity sensing and the wake-on-approach feature.

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Appendix A: Determining the Sense Clock Divider and Modulator Clock
Divider Using SmartSense

For proper CapSense operation, you need to set the sense clock divider and modulator clock divider in the CapSense
CSD Component configuration window. The values for these parameters depend on the C

of the sensor. To

determine the sense clock divider and modulator clock divider values for a sensor using the SmartSense algorithm,
follow these steps.

1. In the PSoC Creator

TopDesign.cysch

window, place the CapSense CSD Component (if not placed already).

Double-click on the CapSense Component to configure the CapSense CSD parameters.

2. In the CapSense Component

General

tab, set the parameters to the values shown in

Figure 32

Figure 32. General Settings Tab in CapSense Component Configuration Window

3. In the CapSense Component

Widgets Config

tab, select the

“Proximity sensors” widget and click

Add

proximity sensor

. Add more proximity sensors as required in your design.

4. In the CapSense Component

Advanced

configuration windows, do the following:

a. If the shield electrode is used in your design, select the

“Enabled” option for the

Shield

parameter. If not,

then

select “Disabled.”

b. Set the

Csh_tank precharge

parameter to

“Precharge by IO buffer.”

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Note:

This only needs to be done if using a shield electrode.

Leave all other parameters at their default values, as shown in

Figure 33

5. In the CapSense Component

Tune Helper

configuration tab, do the following:

a. Select the

Enable tune helper

check box.

b. For the

Instance name for the SCB component

parameter, enter

“EzI2C.”

Click

to save the settings and close the window.

6. In the

TopDesign.cysch

panel, place an EzI2C Slave Component and do the following:

a. Double-click the EzI2C Component and set the parameters to the values shown in

Figure 34.

b. Click

to save the settings and close the window.

Figure 33. Advanced Settings Tab in CapSense Component Configuration Window

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Figure 34. EzI2C Configuration Window

7. In the

main.c

file, do the following:

a. Enable global interrupt.

b. Enable proximity sensors.

Start the CapSense Tuner.

d. Run the tuner in an infinite loop as follows.

In  the  CapSense  Component,  proximity  sensors  are  not  enabled  by  default.  You  should  call  the
CapSense_EnableWidget  (uint32  widget)  API for  each  proximity  sensor  with  the  proximity  sensor  name  as  the
parameter to enable it as follows.

int

main()

{

CyGlobalIntEnable;

CapSense_1_EnableWidget (CapSense_1_PROXIMITYSENSOR0__PROX);

CapSense_1_EnableWidget (CapSense_1_PROXIMITYSENSOR1__PROX);

CapSense_1_EnableWidget (CapSense_1_PROXIMITYSENSOR2__PROX);

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CapSense_1_EnableWidget (CapSense_1_PROXIMITYSENSOR3__PROX);

CapSense_1_TunerStart();

while

(1)

{

CapSense_1_TunerComm();

}

8. In the .

cydwr

file, select the sensor and EzI2C pins and build the project (press

[Shift] [F6]

). Ensure that there

are zero errors in the project.

9. After the project is built without errors, press

[Ctrl] [F5]

to program the device.

10. After the device is programmed, in the

TopDesign.cysch

window, right-

click on the “CapSense CSD” Component

and select “Launch Tuner.”

11. In the CapSense Tuner,

click on “Configuration” and set the parameters to the values shown in

Figure 35

and

click

Figure 35. CapSense Tuner Configuration

12. In the CapSense Tuner, click the

Start

button to read the CapSense CSD parameters set by the SmartSense

algorithm. The sensor parameters are shown in the bottom right of the

Sensor Properties

window. If you have

more than one sensor, select the sensor for which you want to view the sensor parameters at the top right part of
the

Sensor Properties

window, as

Figure 36

shows.

13. Choose

File

Apply Changes and Close

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Appendix B: Reading Sensor Debug Data in the Bridge Control Panel

To tune the CapSense CSD parameters for a sensor, you need to view the sensor data such as the raw count,
baseline, and difference count. For viewing the sensor data, you can use the CapSense Tuner available in the
CapSense Component or use the

Bridge Control Panel

(BCP) tool.

Using the BCP tool, you can view other parameters in addition to the raw count, baseline, and difference count. The
CapSense Tuner requires I

C communication for viewing the sensor data, whereas the BCP tool supports both I

and UART communication for viewing the sensor data.

The example projects provided with this application note support viewing the sensor data in the CapSense Tuner
(using I

C) and the BCP (using UART). This appendix explains how to view the sensor data in the BCP tool through

UART communication. For details on how to use the CapSense Tuner, refer to the

“Manual Tuning”

section in the

PSoC 4 CapSense Design Guide

Table 12

lists the general structure of a UART TX packet sent to the BCP tool.

The TX packet

consists of a header (2

bytes), data (of variable length), and a tail (3 bytes).

Table 12. UART TX Data Packet Structure

Header

Data

Tail

0x0D

0x0A

Variable-length data

0x00

0xFF

Note:

To learn the exact data for any example project, refer to the

.IIC

file provided with it.

Follow these steps to set up the BCP tool for viewing the data:

1. Connect CY8CKIT-040 or CY8CKIT-042 to the PC using the USB cable (USB A to mini-B). If you are using

CY8CKIT-042, connect pin P0[1] on J2 and pin P12[6] on J8 using a wire, as

Figure 24

shows. Ensure that the

TX8_ENABLE macro is set to ‘1’ in the

main.c

file of the project and build the project.

2. Press [

Ctrl] [F5]

to program the CY8CKIT-040 kit or CY8CKIT-042 kit.

3. Open the BCP tool (choose

Start

All Programs

Cypress

Bridge Control Panel <version>

Bridge

Control Panel <version>

4. In the BCP tool, select the CY8CKIT-040 kit or CY8CKIT-042 kit UART-bridge

COM port in the “Connected I2C

/SPI/RX8 Ports:” window and set RX8 as its protocol, as

Figure 37

shows. The CY8CKIT-040 kit or CY8CKIT-

042 kit UART-bridge COM port will be listed in the Device Manager, as

Figure 38

shows.

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5. Choose

Tools

Protocol Configuration

or press

[F7]

and configure the RX8 protocol parameters, as

Figure 39

shows.

Figure 39. RX8 Protocol Configuration

6. Choose

Chart

Variable Settings

Load

and navigate to the example project directory. Select the

<Project_Name>.ini

file and click

Open

. Click

to apply the settings and close the window, as shown in

Figure

Figure 40. Bridge Control Panel

– Variable Settings

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7. Choose

File

Open File

and select the

<Project_Name>.iic

file provided with the project and click

Open

8. Place the cursor on the command line and then click

Repeat,

Figure 41

, shows to start receiving the packets.

9. To view the sensor data in a graphical format, click on the

Chart

tab. Uncheck the

Select All

option and check

the

and

options to view the raw count and baseline, as shown in

Figure 42

. Similarly, you can view the

difference count (

) and the average filtered data.

Figure 41. Reading CapSense Debug Data in Bridge Control Panel

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Appendix C: Advanced Low-Pass Filter API Definitions

Table 13

lists the ALP filter APIs.

Example Project 1

– Proximity Distance

shows how to use these APIs

Table 13. Advanced Low-Pass Filter Definitions

CapSenseFilters_SetAdvancedLowPassK

Description

This API sets the filter coefficient (K-value) for the ALP filter.

Prototype

void CapSenseFilters_SetAdvancedLowPassK(CAPSENSEFILTERS_IIR_K_ENUM k)

Parameters

Following is the Enum type definition used by this API:

typedef enum
{
CAPSENSEFILTERS_IIR_K_2 =   0x01,
     CAPSENSEFILTERS_IIR_K_4   =   0x02,
     CAPSENSEFILTERS_IIR_K_16 =   0x04,
     CAPSENSEFILTERS_IIR_K_32 =   0x05,
     CAPSENSEFILTERS_IIR_K_64 =   0x06
} CAPSENSEFILTERS_IIR_K_ENUM;

The K-value of the ALP filter determines the attenuation of noise in the proximity sensor raw counts.

Noise attenuation decreases in the order CAPSENSEFILTERS_IIR_K_64 > CAPSENSEFILTERS_IIR_K_32 >
CAPSENSEFILTERS_IIR_K_16. The CAPSENSEFILTERS_IIR_K_4 and CAPSENSEFILTERS_IIR_K_2 are used for
compatibility purposes and should not be used. Refer to the

ALP Filter Tuning

section to set this parameter.

Return value

None

CapSenseFilters_InitializeAdvancedLowPass

Description

This API initializes the internal history of the specified sensor to the specified raw count value.

Prototype

void CapSenseFilters_InitializeAdvancedLowPass(uint32 sensorId, uint16
initializationRawValue)

Parameters

sensorId:

This parameter indicates the sensor number for which the ALP filter history is to be initialized to a given

initializationRawValue

initializationRawValue:

This is the value to which the filter history gets initialized. This value should be equal to

the sensor raw count.

Return value

None

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CapSenseFilters_RunAdvancedLowPass

Description

This API applies the ALP filter to the raw count of the proximity sensor. Filtered data is stored back in the raw count array.

Prototype

void CapSenseFilters_RunAdvancedLowPass(uint32 sensorId)

Parameters

sensorId:

This parameter indicates the sensor number on which the filter is to be applied.

Return value

None

CapSenseFilters_ResetAdvancedLowPass

Description

This API resets the ALP filter for a given

sensorId

. Resetting the ALP filter ensures that the filter history is automatically

reinitialized the next time the

“CapSenseFilters_RunAdvancedLowPass()” API is called.

Prototype

void CapSenseFilters_ResetAdvancedLowPass(uint32 sensorId)

Parameters

sensorId:

This parameter indicates the sensor number for which the filter is to be reset.

Return value

None

CapSenseFilters_GetAverageData

Description

This API returns the output of the average filter for the specified sensor (

sensorId)

Prototype

uint16 CapSenseFilters_GetAverageData(uint32 sensorId)

Parameters

sensorId:

This parameter indicates the sensor number for which the

averageVal

is to be read.

Return value

averageVal[sensorId]

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CapSenseFilters_GetALPFilterState

Description

This API returns the current state of the ALP filter.

Prototype

CAPSENSEFILTERS_ALP_STATE_ENUM CapSenseFilters_GetALPFilterState (uint32 sensorId)

Parameters

sensorId:

This parameter indicates the sensor number for which the ALP filter state is to be read.

Return value

stateAdvancedFilter [sensorId]

Following is the Enum type definition used by this API:

typedef enum
{

CAPSENSEFILTERS_ALP_STATE_UNINITIALIZED

= 0x00,

CAPSENSEFILTERS_ALP_STATE_IDLE

= 0x01,

CAPSENSEFILTERS_ALP_STATE_POS_EDGE_TRACK

= 0x02,

CAPSENSEFILTERS_ALP_STATE_SIGNAL_DETECTED

= 0x03,

CAPSENSEFILTERS_ALP_STATE_NEG_EDGE_TRACK

= 0x04,

CAPSENSEFILTERS_ALP_STATE_NEG_SPIKE

= 0x05

} CAPSENSEFILTERS_ALP_STATE_ENUM;

UNINITIALIZED state indicates that the filter history variables are not initialized.
IDLE state indicates the normal operation of a sensor when there is no target object near the sensor. A slow response
filter is applied in this state.
POS_EDGE_TRACK state indicates that there is a target object approaching the sensor. A fast response filter is applied
in this state.
SIGNAL_DETECTED state indicates that the target object is detected. A slow response filter is applied in this state.
NEG_EDGE_TRACK state indicates that the target object is receding from the sensor. A fast response filter is applied in
this state.
NEG_SPIKE state indicates an unexpected negative noise on the sensor raw count. This state is not expected to occur
during normal sensor operation.

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Appendix D: Adding the ALP Filter Library to Any CapSense Project

If you want to add an ALP filter to your project, follow the below steps. This section assumes that you already have a
PSoC Creator project with proximity sensor implemented.

1. Download the ALP_Filter_Library.zip file from

http://www.cypress.com/AN92239

2. Extract the files from

ALP_Filter_Library.zip

and open the folder ALP_Filter_Library.

3. The library file is provided for three compilers. Depending on the compiler used in your project, select the

libCapSenseFilters.a

file from the specific compiler folder and copy it to the location where

main.c

is located.

For example, if you are using

ARM GCC 4.8.4

complier, open

ALP_Filter_Library

ARM_GCC_473

and select

the

libCapSenseFilters.a

file and copy it to the project location where

main.c

is located.

4. Copy header file

CapSenseFilter.h

and

CyBitOperations.h

to project location where

main.c

is located

5. Open your project in

PSoC Creator

6. Click on

Project

menu and select

Build Settings

7. In the Build Settings window, specify the

Configuration

option as

Release

Debug

based on your requirement

and follow the steps mentioned below

8. Select the required complier from the

Toolchain

option. For example, if you want to use

ARM GCC 4.8.4

then

select

ARM GCC 4.8.4.

The next steps assume that the compiler is selected as

ARM GCC 4.8.4

. If you are

using a different compiler, you can follow the same steps.

9. Expand the

ARM GCC 4.8.4

list in the left-most column as shown in #2 in

Figure 43

, and click on

Linker

shown in #3 in

Figure 43

. In the

General

tab of

Linker

menu, click on

Additional Libraries,

shown in #4 in

Figure 43

and type

CapSenseFilters

then click

as shown in #5 in

Figure 43.

Note: If you want to use both

Release

and

Debug

configuration, you need to repeat

step

for both the

configurations.

Figure 43. Adding ALP Filter Library Files to PSoC Creator

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10. Add the library header files to your project by following the below steps.

Navigate to

Workspace Explorer

and right-click on

Header Files

and select

Add > Existing Item

Navigate to <

your project location

>-> <

project name.cydsn

> >. In the explorer, press

Ctrl

and select

CapSenseFilters.h

and

CyBitOperations.h

files and click

Open,

Figure 44

and

Figure 45

shows.

Figure 44. Adding Header Files to PSoC Creator Project

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Document No. 001-92239 Rev. *B

Figure 45. Adding ALP Filter Definition Files to the PSoC Creator Project

11. In the

main.c

file, include

CapSenseFilters.h

by using following line of code:

# include “CapSenseFilters.h”

12. Define the ALP thresholds by using the following lines of code:

/* Positive and Negative threshold used by ALP filter.
* Refer AN92239 for details on how to tune positive and negative thresholds.
*/

#define

PROX_POS_THRESHOLD

(100u)

#define

PROX_NEG_THRESHOLD

(100u)

Note:

The

procedure to find out ALP thresholds is mentioned in section

ALP Filter Tuning

See the

main.c

of the example project Proximity_Distance_040 for details on where to place code for defining

ALP filter thresholds.

13. Declare ALP filter variables by using the following lines of code:

/* ALP Filter variables */

/* Thresholds for adjusting ALP filter response */

uint8 proxPositiveTh[CapSense_TOTAL_PROX_SENSOR_COUNT];
uint8 proxNegativeTh[CapSense_TOTAL_PROX_SENSOR_COUNT];

/*Average Filter history */

uint16 averageHistory[CapSense_TOTAL_PROX_SENSOR_COUNT][AVERAGE_HISTORY_SIZE];

/* Indicates the oldest data amongst Average Filter histories */

uint8 avgOldestDataIndex[CapSense_TOTAL_PROX_SENSOR_COUNT] = {0};

/* State variable for ALP filter state machine */

CAPSENSEFILTERS_ALP_STATE_ENUM stateAdvancedFilter[CapSense_TOTAL_PROX_SENSOR_COUNT];

/* Average Filter output */

uint16 averageVal[CapSense_TOTAL_PROX_SENSOR_COUNT];

/* Following variables contain input histories for ALP filter */

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uint16 filterHistory0[CapSense_TOTAL_PROX_SENSOR_COUNT];
uint16 filterHistory1[CapSense_TOTAL_PROX_SENSOR_COUNT];

uint16 filterHistory2[CapSense_TOTAL_PROX_SENSOR_COUNT];

Note:

See the

main.c

of the example project Proximity_Distance_040 for details on where to place the code to

declare ALP filter thresholds.

14. In the main() function in main.c, initialize the proximity positive, negative threshold, initialize advanced low pass

filter with current raw of sensor and setting the k value for ALP filter by using following lines of codes

/* Initialize the proximity positive and negative threshold values */

proxPositiveTh[CapSense_SENSOR_PROX_0__PROX] = PROX_POS_THRESHOLD;
proxNegativeTh[CapSense_SENSOR_PROX_0__PROX] = PROX_NEG_THRESHOLD;

/* Initialize Advanced Low Pass (ALP) filter variables with current raw count value */

CapSenseFilters_InitializeAdvancedLowPass(

CapSense_SENSOR_PROX_0__PROX,

CapSense_ReadSensorRaw(CapSense_SENSOR_PROX_0__PROX)

);

/* Set the k value for ALP filter */

CapSenseFilters_SetAdvancedLowPassK(CAPSENSEFILTERS_IIR_K_64);

Note

: The parameter < CapSense_SENSOR_PROX_0__PROX> is the sensor number for the proximity sensor.

You need to replace this parameter with the proximity sensor # from your project

See the

main.c

of the example project Proximity_Distance_040 for details on where to place the code to declare

ALP filter thresholds

15. The value of the argument to the function CapSenseFilters_SetAdvancedLowPassK() depends on the peak-to-

peak noise in the raw count. Use peak-to-peak noise value to set the K-value per mapping in

Table 6

16. In the main.c function, enable the ALP filter by using following code just after

while

(CapSense_IsBusy()) code

CapSenseFilters_RunAdvancedLowPass(CapSense_SENSOR_PROX_0__PROX);

Note

: See the

main.c

of the example project Proximity_Distance_040 for details on where to place the ALP code

in your project.

17. Build the project, ensure that the project compiled without any errors.

18. Observe the raw count data and confirm that the ALP filter has reduced the noise in raw counts.

19. To tune the ALP filter, follow the procedure given in section

ALP Filter Tuning

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Document History

Document Title: AN92239 - Proximity Sensing with CapSense

Document Number: 001-92239

Revision

ECN

Orig. of

Change

Submission

Date

Description of Change

4421289

DCHE

07/22/2014

New Application Note

4897476

AKSM

09/04/2015

Added section 10 Design Consideration to Achieve 30-cm Proximity-Sensing
Distance

Added Appendix D: Adding the ALP Filter Library to Any CapSense Project

Updated Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 12, Figure 22,
Figure 23, Figure 24, Figure 25, Figure 26, Figure 27, Figure 28, Figure 30, Figure
31, Figure 32, Figure 33, Figure 34, Figure 35, Figure 36

Changed template of AN

5094088

VAIR

01/20/2016

Added Glossary.

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cypress.com/go/memory

PSoC

cypress.com/go/psoc

Touch Sensing

cypress.com/go/touch

USB Controllers

cypress.com/go/usb

Wireless/RF

cypress.com/go/wireless

PSoC

Solutions

psoc.cypress.com/solutions

Cypress Developer Community

Technical Support

cypress.com/go/support

PSoC is a registered trademark and PSoC Creator is a trademark of Cypress Semiconductor Corp. All other trademarks or registered trademarks
referenced herein are the property of their respective owners.

Cypress Semiconductor
198 Champion Court
San Jose, CA 95134-1709

Phone

: 408-943-2600

Fax

: 408-943-4730

Website : www.cypress.com

©  Cypress  Semiconductor  Corporation,  2014-2016.  The  information  contained  herein  is  subject  to  change  without  notice.  Cypress  Semiconductor
Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any
license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or
safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as
critical  components  in  life-support systems  where  a  malfunction  or failure  may  reasonably  be  expected  to  result  in significant  injury  to the  user.  The
inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies
Cypress against all charges.
This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide
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personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative
works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress
integrated  circuit  as  specified  in  the  applicable  agreement.  Any  reproduction,  modification,  translation,  compilation,  or  representation  of  this  Source
Code except as specified above is prohibited without the express written permission of Cypress.
Disclaimer:  CYPRESS MAKES  NO WARRANTY OF  ANY  KIND,  EXPRESS  OR  IMPLIED, WITH  REGARD  TO  THIS  MATERIAL, INCLUDING,  BUT
NOT  LIMITED  TO,  THE  IMPLIED  WARRANTIES  OF  MERCHANTABILITY  AND  FITNESS  FOR  A  PARTICULAR  PURPOSE.  Cypress  reserves  the
right to make changes without further notice to the materials described herein. Cypress does  not assume any liability arising out of the application or
use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a
malfunction or failure may reasonably be expec

ted to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems

application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Use may be limited by and subject to the applicable Cypress software license agreement.