capacitive touch

Touch Technology

Touch Technology An Overview

Touch Technology

Table of Content Atmel’s Touch Technology

Division

Market presence

Technology Overview

Changing product design

Competing Technologies

Software Library

Touch screen solutions

Summary

Touch Technology

Atmel’s Touch Technology Division

Founded as Quantum Research

Group in 1996

Located in Southampton,

UK

Part of Atmel corp since March 2008

Solutions in production for

>12 years

Leaders in capacitive sensing

technology

Technology: charge-transfer

Substantial patent base

Flexible Business Models

Touch Technology

Market success to date

Mobile handsets Shipped in over 50M handsets

Over 200M buttons rotors and sliders in handsets

Over 5m touchscreens

Customers include Nokia, Motorola, Samsung, Bird, Sagem and Toshiba.

Note books Shipped over 2 million buttons and sliders

Buttons and sliders for function keys

On/Off buttons

Shipping in models for HP, Dell and Lenovo

Touch Technology

Market Success

Kitchen Appliances Shipping in appliances for over 8 years successfully

More that 20 design wins in various global manufacturers

Applications in cooker hobs, cooker hoods (extractors) microwave controls, refrigerator controls and dishwasher controls.

Customers include LG Appliances, GE, Whirlpool, Electrolux, Gorenje, Samsung, Haier

Consumer Electronics Multiple wins in desktop monitors

Multiple wins in MP3 apps

Customers include Apple, Philips, Samsung, LG, Bose, Logitech, Neovo, Asus, Acer

Touch Technology

Technology Overview

For 1 to 10 buttons Simple key shapes Easy to wire

QTouch™ QSlide™QWheel™

Linear touch Rotary touch 3 channels High resolution

QMatrix™

Up to 48 keys Water resistant High temperature

QField™

QTwo™

Single-touch screens

Multi-touch screens

Functionality also implemented through Atmel Touch Software Library™ – part of AVR® studio

Touch Technology

QTouch™

QTouch – simple solution 1-10 keys

1.8V operation Low power operations UART, SPI and I2C Always stays calibrated Patented Adjacent Key Suppression™(AKS™)

Supports small keypads

Small footprint – ideal for mobile devices Supports clear discrete button touch screens Most popular in the consumer market

QTouch – Popular in consumer market

Touch Technology

8

QTouch Basics: Goals

Detect finger presence near electrode

Electrode behind a dielectric panel so no direct galvanic connection to measuring circuit

Electrode

Measuring Circuit

Measuring Circuit

Touch Technology

9

QTouch Basics: Charge Transfer Basics

Cs >> Cx example (1000:1 ratio)

Cs = 10nF Cx = 10pF

S1,S2 and S3 are CMOS IO pins switching between GND, Z and Vdd

Cs

GND

GND

VDD

S1

S2

S3

Sampling capacitorMCU

CxEART

H

Touch Technology

QTouch™: Charge Transfer Basics

Uses a switched capacitor method employing a “sampling” capacitor Cs Usually 1000+ times bigger than the sense electrode capacitance Cx (normally around 1pF to 10pF)

The sense electrode is just an “open circuit” pad We measure the “self capacitance” of this pad

Touch Technology

QTouch™: Charge Transfer Basics

Cs is switched using “bit banging”

A series of voltage pulses cause current to flow in Cs and Cx Charge on Cs builds up by each pulse Cx is discharged after each pulse

The voltage over the Capacitor (U = Q/C) builds up as well

We measure the voltage by checking a digital input Like a comparator, comparing vs VIH

We measure the number of pulses to reach VIH

When we touch the sensor, the number of pulses will be decreased

Touch Technology

12

QTouch Basics: Charge Transfer Basics

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Touch Technology

13

Step 1: Discharge Cx and Cs

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Create Initial condition: Takes time

Touch Technology

14

Step 2: Float Cs

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Prevents cross-conduction between P and N-channel transistors in *some* MCU IO cellsWell designed I/O blocks does this automatically

Touch Technology

15

Step 3: Charge Transfer

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Rising edge on SNS pin drives charge through Cs into Cx

Touch Technology

16

Step 4: Float Cs and settling time

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Touch Technology

17

Step 5: Measure Vcs and discharge Cx

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

SNS = Vcs

SNSK = Gnd

Touch Technology

18

Step 5: Measure Vcs and discharge Cx

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

SNS = Vcs = VDD * (Cx / (Cs + Cx))

Cs = ~ 1000 * Cx

Vcs = VDD / 1000

Qs = Cs * Vcs

Qx = Cx * Vx

Vx == 0 ==> Qx == 0 SNSK = Gnd

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19

Repeat 1 - 5:

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Vcs = VDD / 1000 initially

Add approximately 0,999 * VDD * (Cx / (Cs + Cx))

Gnd

Qs = Cs * Vcs

Touch Technology

Continuously add charge to Cs

VIH

When Vcs reached VIH, the I/O port will read as ”1”.

Touch Technology

Real Waveform

Vcs

Time

Vdd

Touch Technology

Charging Waveform

Vsns

Time

Vih

Vdd

Vsnsk

Time

Vdd

Touch Technology

Normal mode

Typically uses ~200 pulses to reach VIH

Typical burst length = 500 us .. 5 ms Long burst lengths mainly for proximity detection

Run several bursts before declaring detection ”Detect integration - DI”

Similar to debouncing

DI count normally from 3 upwards, 10 = common

Hysteresis: detection level changes on detect

Touch Technology

24

Add a finger => Ct increase

Cs

Sampling capacitor

MCU

CxEART

H

GND

VDD

S2

S3

GND

S1

Vcs = VDD / 1000 initially

Add approximately

0,999 * VDD * (Cx//Ct / (Cs + Cx//Ct))

Gnd

Qs = Cs * Vcs

CtEARTH

Touch Technology

Effect of increasing Ct

The charge added each pulse will increase.

Cs will charge faster, than if no finger is present

VIH is reached faster

Fewer pulses are needed

Burst time gets shorter

Burst change (delta) is proportional to Ct

Touch Technology

Continuously add charge to Cs

VIH

When Vcs reached VIH, the I/O port will read as ”1”.

No fingerFinger present

Touch Technology

QTouch™: Sensitivity

Larger key surface area = more sensitivity

Sampling Capacitor, Cs controls sensitivity Increasing Cs = Increased differential sensitivity

makes the burst length longer

Improves resolution

Simple tuning procedure Changing a single capacitor value per key

Can be done without software

One time tuning for a design

Touch Technology

Technology Overview




QMatrix™


QField™

QTwo™


Multi-touch screens


Touch Technology

QMatrix™

• UART, SPI and I2C• Efficient X-Y interleaved electrodes • Support up to 48keys • Low power operations• 1.8V operation• Always stays calibrated• Available in small packages (up to 24 Keys)• Patented Adjacent Key Suppression™(AKS™) for small keypads• Low power and small footprint – ideal for mobile devices• Supports clear discrete button touch screens• Most popular in the consumer market

QMatrix - Popular in appliance market and mobile market

Touch Technology

Self Capacitance

Touch Technology

Mutual Capacitance

Touch Technology

Mutual Capacitance

…

Touch Technology

Mutual Capacitance

Touch Technology

QMatrix™: Charge Transfer Basics

Also uses a switched capacitor method employing a “sampling” capacitor Cs that is usually 1000+ times bigger than

the sensor capacitance Cx (normally around 1pF to 5pF)

The sensor in this case is formed at the “intersection” of two electrodes, X (transmitter) and Y (receiver).

In other words QMatrix measures the *mutual* transverse (usually) coupling capacitance between X and Y

X and Y Fixed number of voltage pulses Each pulse cause current to flow in Cx and Cs (in series with each other) Current only flows in selected pairs or Cx and Cs. This is how a sequential matrix scan is achieved

The voltage on Cs builds up pulse-by-pulse and after the fixed number of pulses is done, the voltage on Cs is measured to give us our reading

Touch Technology

QMatrix™: Charge Transfer Basics

Cs

GND

GND

VDD

S1

S2

S3 Sampling capacitor

MCU

CxGND

S4

X

Yk

Y

Vyk

|Vcs|

Time

Approximately linear

0.25V

Approximately linear

Vsns

Time

-0.25V

t

Terminal voltage

Y0

Y1

X0

X1

X2

X3

Touch Technology

QMatrix™ : Measuring Technique

We can use Atmel AVRs e.g. Tiny44/84/88, Mega48/88/168 (including PicoPower), Mega164P/324P for QMatrix because they have the

required internal comparator + counter/capture registers

Cs

GND

GND

VDD

S1

S2

S3

MCU

CxGND

S4

X

Yk

Y

Rsmp

SMP

CAPTURE

CTR CLK

+-

VDD

S5

GND

S6

Vcs

Time

Touch Technology

QMatrix™ Basics: What Happens During Touch ?:

Now we bring a finger close to electrode

This diverts charge from Cx, and so away from Cs

So each charge pulse now charges Cs by a smaller amount

This means charge builds up in Cs less quickly

So if each pulse deposits less charge, then Vcs rises slower, so

reaches a smaller terminal voltage

needs less time to discharge to GND

so counter value gets less

count change (delta) is proportional to Ct

E-field

X Y EARTH

Ct

Vcs

Time

No touch

Delta

Time

Touch

Vcs

Touch Technology

QMatrix™: Sensitivity

Optimise key designs for improved sensitivity and SNR

Increasing Burst Length (number of charge pulses), increases sensitivity Software based tuning Does not require component changes

Increasing Rsmp, increases signal resolution

One time tuning for a design

Touch Technology

Best in class solutions: Excellent signal-to-noise ratio Excellent field penetration Spread spectrum modulation Failure mode detection Best in class EMC characteristic

Ease of design: Highly integrated solutions Reference designs

Flexible: Standard or custom products User developed solutions

Cost effective

Atmel’s Charge Transfer Technology

QMatrix™ charge transfer principle

Touch Technology

Technology Overview




QMatrix™


QField™

QTwo™


Multi-touch screens


Touch Technology

Usable over LCD display iPod-type functionality Low voltage, low power Slider/Wheel available in

QTouch devices: QT1106 Slider available in QMatrix

device: AT42QT2160 Only three channels used to

make a 256 position absolute scroller

QSlide™ & QWheel™ - Easy scrolling

QSlide/QMatrix - Popular in personal media devices

Touch Technology

QSlide™ & QWheel™: QTouch™

i) Small 10-12mm dia

ii) Medium 12-16mm dia iii) Large 16-40mm dia

i) Small 20-25mm long

ii) Medium/Large 25-60mm long

Touch Technology

QSlide™ & QWheel™: QMatrix™

X0 X1 X2 X3

Y

Y

X0

X1

X2

X3X4

X5

X6

X7One Layer Designs

Touch Technology

QSlide™ & QWheel™: QMatrix™

2 Layer Designs - Flooded X

Increases design possibilities

Improved directional noise immunity

Y

X0

X1

X2X3

X4

X5

Y

X0 X1 X2 X3

Touch Technology

QSlide™ & QWheel™ : Touch Position

A BSS

XX

L E F T RI G H TRI G H T

A

BC

Uses geometric calculations in between 2 points (channels) to determine absolute touch position

Touch Technology

Capacitive sensing - changing product design

Flexible No longer restricted to

using buttons

Increasing focus on industrial design

UI innovation with multi-touch

Innovative Slimmer products - no

mechanical parts required

Easy to clean

Hidden until lit

Touch Technology

Other Markets

Capsensing is not only for Mobile and appliances….Atmel have many design wins in …..

Medical

Automotive

Industrial

Vending

Security

Toys

Touch Technology

Atmel Industry Presence : recent design wins

ConsumerMobile and PND

Mobile phonesSmart phones

HeadsetsPNDs

LaptopsDigital photo frames

TVs and Home cinemasStereos and speakers

MP3 players

Appliance

OvensRefrigerators

Washing machines

Touch Technology

Atmel advantages

Early market entry – long experience

Addresses many diverse markets

Robust solution Very few competitors are even close

Competitor analysis data available on request

Touch Technology

Differentiation: Atmel Touch Sensors Very high signal to noise ratio

Makes designs easier from the outset

Supports small sensors

OK in noisy environments

Broad range of key sizes & shapes due to size of integration capacitors

Inherent flexibility of technology

Key patent for close pitched key arrays Adjacent Key Suppression (AKS™)

Touch Technology

QMatrix Strong suppression of moisture effects

Due to X and Y electrode design and touch aquisition

Remote placement of chip Sensitive to X/Y crossing

Not sensitive to X lines

Not sensitive to Y lines

Touch Technology

QTouch/QMatrix on AVR AVR has plenty of processing power.

Can complete sensing faster

Can spend more time in sleep

Minimal amount of H/W needed Chip resource available for other applications

Lower power consumption

Broad range of applications with a lower cost chip

Touch Technology

Q-Touch/Q-Matrix libraries

Empowering Atmel AVR users with

Touch Sensor Technology

Touch Technology

Aims of libraries

Flexible, high performance capacitive sensing firmware

Well proven capacitive sensing solution

Support for buttons, sliders and wheels

Easy to implement

No license fee

Can coexist with user application

Touch Technology

Advantages of the Atmel Code Module

Recognised industry leading Charge Transfer technique Best signal to noise ration

Makes designs fundamentally easier to implement

Flexible implementation arbitrary key sizes & shapes no need to balance channels

All digital technique None of the disadvantages of analogue sensing techniques

Easy implementation using Quantum reference designs

Access to key Atmel/Quantum patents Adjacent Key Suppression

Touch Technology


Uses AVR as the hardware platform AVR32, Cortex-M3 to follow

Industry leading microcontroller price / performance

Lowest power consumption

Broad product range can be developed & implemented

Fully flexible user implementation

Touch Technology


Simple, easy to implement code library Robust front end capacitive acquisition

Highly experienced Quantum Atmel team Applications / implementation support

Low cost solution

No license cost

Support provided by the Atmel FAE’s

Touch Technology

Code Module Availability

Code modules will be available in two basic versions QTouch module – recommended as first approach

- High sensitivity

- High system noise tolerant

- Easy design

QMatrix module- Less pins needed for 3+ channels

- More tolerant of moisture and ground loading

- Electrode design needs care

Support packages available in both cases Library module and API GUI front end Evaluation module & PC Application Software Reference implementation & application note

Touch Technology

Atmel Touch Software Library - Flexible

Available on standard Atmel parts using libraries in AVR studio

Environmental changes tracked and compensated

Error conditions detected and corrected

Works seamlessly with main device application

For volume programs, application and code development available

Atmel TouchSoftwareLibrary

Host App

Host App

Atmel TouchSoftwareLibrary

Touch Technology

Atmel Capacitive Touchscreen Solutions

Two Touch™ and Single Touch Touchscreens

Roadmap for Touchcreens

January 2009

Touch Technology

Projected Capacitive Touch Screens

Sensors realised with patterned conductors Usually realised using ITO/PET or ITO/Glass

Mostly 2+ layers, Atmel’s solution supports single layer sensors

Multiple sensing elements

Sequential sensing

Atmel’s QField™ technology

Advantages Excellent signal to noise ratio

Accuracy across the whole surface

Can support multiple touches

Senses through ‘thick’ dielectric materials

No user calibration needed

Touch Technology

Introducing the QT5000 Family

Two Touch™ for the most intuitive user interfaces

Touch Technology

QT5000 Family Unique Value

The QT5320 and the QT5480 are single chip Two Touch™ touchscreen controllers supporting

single and two finger touch

Currently up to 48 channels (8X x 6Y)

Supports Single Touch and Dual Touch

Many common touch gestures integrated

Standard touchscreen reference designs available

Highly user configurable interface

Small 5mm x 5mm BGA package

Low power, low voltage

Touch Technology

Introducing the QT4000 Family

Touchscreen solution with single layer sensors for the thinnest possible implementation

Touch Technology

QT4000 Family Unique Value

The QT4120 and the QT4160 are single chip touchscreen controllers enabling single layer

sensor designs

Currently up to 16 channels (4X x 4Y)

Supports Single Touch with Single layer sensors

Many common gestures integrated

Reference designs standard screen sizes

Small 5mm x 5mm QFN package

Low power, low voltage

Touch Technology

Components and Supply Chain

Atmel provides Touch controller IC

Controller board reference design

Sensor reference design

Integration support

Sensor test equipment design

Atmel Partners provide Tested and qualified sensor film

Integration of sensor and front panel

Production controller board

Note: Solution with integrated sensor, front panel and LCD can delivered

Touch Technology

Target Applications

Touch Technology

User Interface in Mobile Phones

Touchscreen mode Managing the address book

Managing the photo album

Fixed keys and sliders On/Off keys

Special function keys

Volume controls

Touch Technology

User Interface in Media Players

Touchscreen mode Music control

Photo control

Zoom and Rotate



Volume controls

Touch Technology

User Interface in Navigation Systems

Touchscreen mode Controlling the maps

Zooming in and out



Touch Technology

Other Target Applications

Digital still cameras

Digital picture frames

Appliance control

Gaming devices

PDAs

Displays

Touch Technology

Easy System Designs

Touchscreens, sliders, wheels and/or keys, selectable by the host via the I2C compatible interface

Touch Technology

Appendix

Atmel’s Portfolio of Touch Sense Products

Touch Technology

QTouch™ - Key std. Products

Part Channels Package Temp. (OC) Eval.Board

QT100A 1 WSON-6 -40 to +85 E100S

QT220 2 SSOP-20 -40 to +85 E240B

QT240 4 SSOP-20 -40 to +85 E240B

QT1080 8 QFN-32 -40 to+85 E1080

QT1101 10 QFN-32 -40 to +85

QT1081 8 QFN-32 -40 to +85 E1081

QT1103 10 QFN-32 -40 to +85 E1103

QT1106 7 + Slider or Wheel

QFN-32 -40 to +85 E1106

AT42QT1040

4 QFN-28 -40 to +85 AT42EVK1040

AT42QT1060

6 QFN-28 -40 to +85 AT42EVK1060

Devices for 1 to 10 keys and/or sliders/wheels

Touch Technology

QMatrix™ - Key std. Products

Part Channels Package Temp. (OC) Eval Board

QT60160 16 QFN-32 -40 to +85 E6240

QT60168 16 TQFP-32 -40 to +105 E6248

QT60240 24 QFN-32 -40 to +85 E6240

QT60248 24 TQFP-32 -40 to +105 E6248

QT60326 32 TQFP-44 -40 to +105 E6486

QT60486 48 TQFP-44 -40 to +105 E6486

AT42QT2160 16

1 Slider

QFN-28 -40 to +85 AT42EVK2160

Controlling up to 48 keys and/or sliders/wheels

Touch Technology

Atmel Touch Library

AT42EVK2080A – QTouch module with ATmega88 target device Hardware module – user can view and evaluate trial implementations of

firmware 10 x ATMega88 IC’s

AT42EVK2080B – QMatrix module with ATtiny88 target device Hardware module – user can view and evaluate trial implementations of

firmware 10 x ATMega88 IC’s

Common to both evaluation modules Installation CD for PC configurator software Quickstart guide including basic operating / flashing instructions / what

hardware required Debug interface allowing rapid visualisation of the pre-processed capacitive

signals for diagnostics API document Description of interface & how to use Reference implementation Compile instructions Links to useful sources of additional code PC debug application for tuning implemented systems

Touch Technology

QField and QTwo Touchscreen Products

Easy to Use Touchscreen Controllers Part Total

nodesPackage Touch Screen

SizeEval Board

AT42QT4120 12 (4x3) QFN-32 Single touch 3.2” EVK4120A/B

AT42QT4160 16 (4x4) QFN-32 Single touch 4.3” EVK4160A/B

AT42QT5320 32 (8x4) QFN-32 Single touch

/Two touch

4.3” EVK5480x

AT42QT5480 48 (8x6) BGA-49 QFN-

44 TQFP-44 Single touch

/Two touch

8” EVK5480x

capacitive touch

Documents

touch technology repeat

time touch technology

pad touch technology

linear touch rotary

sampling capacitor cs

capacitive sensing technology

cs vih

atmel touch software