ATMEL Capacitive Touch Technology

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Agenda

Common User Interfaces Why Capacitive Touch Sensing? Charge Transfer Technology Self Capacitance Sensors Mutual Capacitance Sensors Proximity Sensors Slider and Rotor Design

Atmels Touch Solutions Buttons/Sliders/Wheels Software Library Touch Screen

Why Choose Atmel?

Common User Interfaces

n Mechanical Cost leading technology Dominant Prone to failures

Buttons and Sliders

n Resistive Complex and costly system design

n Optical Infrared buttons mainly in appliances Expensive and unreliable

n Capacitive Direct implementation on PCB Flexible sensor size and shape Lowest system cost.

Common User Interfaces

Touch Screens

Resistive Pressure required, easily damaged Low transparency

Surface Acoustic Wave Complex to design, expensive

Inductive Expensive, inflexible

n Capacitive - Easy to implement, flexible, cost effective

Agenda

Common User Interfaces Why Capacitive Touch Sensing? Charge Transfer Technology Self Capacitance Mutual Capacitance Proximity Slider and Rotor Design

Atmels Touch Solutions Buttons/Sliders/Wheels Software Library Touch Screen

Why Choose Atmel?

Why Capacitive Touch Sensing?

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 Added Functionality

Reliability Inherent ESD protection Increased environmental protection

Agenda

Common User Interfaces Why Capacitive Touch Sensing? Charge Transfer Technology Self Capacitance Mutual Capacitance Proximity Slider and Rotor Design

Atmels Touch Solutions Buttons/Sliders/Wheels Software Library Touch Screen

Why Choose Atmel?

Capacitive Touch Method: Charge Transfer

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

Ease of design:n Highly integrated solutions n Reference designs

Flexible:n Standard or custom products n User developed solutionsQMatrix charge transfer principle

Cost effective

Self Capacitance: Basics

Measuring Circuit Electrode

Electrode is a single conductive plate 2nd Plate of capacitor is circuit or earth ground Electrode is behind a dielectric panel so no direct galvanic connection to measuring circuit when touched

Self Capacitance: Equivalent CircuitVdd

CtMCUEARTH

Cs: Sampling capacitor (1-100nF) Cx: Electrode capacitance to earth (2-10pF ?) Ct: Touch capacitance to earth (few pF)

Cs CxEARTH

Cf: Coupling capacitance between circuit GND and earth (few pF)

CfGNDEARTH

GND is the PCB ground EARTH is earth ground Assume Cs >> Cx, and Cf >> Cx & Ct Cx and Ct are of interest to us Really just interested in capacitive delta when electrode touched

Self Capacitance: Charge Transfer Basics

MCU

Sampling capacitor

CtEARTH

S1GND VDD

CsEARTH

S2 S3GND

Cx

Vsns Vdd

Vcs Vdd

Vih

Time

Time

Self Capacitance: Touch vs. No Touch?

Now bring a finger close to the sense electrodeE-fieldVsnsk

Ct added in parallel to Cx Each charge pulse now charges Ct // Cx

No touch

Charge builds up in Cs more quickly As each pulse deposits more charge, Vcs rises faster so.. we reach Vih more rapidly we need fewer pulses

Time Vsnsk

Touch

burst time gets shorter burst change (delta) is proportional to Ct

Time

Delta

Self Capacitance: Button Design with LEDs

LED Lighting can be done easily by using a back lighting LED on the opposite side of the PCB Keep hole as small as possible to eliminate possible dead spots in key LEDs may need a bypass capacitor to protect against the LEDs change in capacitance

Mutual Capacitance: Basics

Measuring Circuit Electrode array Sensor consists of X and Y electrodes. Cx capacitance formed between X and Y electrodes. More efficient IO utilization for high key counts. Electrode is behind a dielectric panel so no direct galvanic connection to measuring circuit when touched

Mutual Capacitance: Basics

X and Y are generally inter-digitated (i.e. they form interlocking fingers Field lines are mostly contained between X and Y electrodes X is drive line. Y is receive line Strong water film suppression water film moves signal away from touch

Mutual Capacitance: Equivalent CircuitMCU VDD S2 S4 GND S1 GND Cs Yk Cx X

Cs: Sampling capacitor (4.7-22nF) Cx: Electrode self coupling capacitance (2-10pF ?) Ct: Touch capacitance to earth (few pF)

S3 GND GND

Y Sampling capacitor

Cf

Cf: Coupling capacitance between circuit GND and earth (few pF)

Earth

GND is the local circuit return EARTH is the free space return We are interested in Cx and Ct primarily Different technique to Self Capacitance

Mutual Capacitance: Charge Transfer Basics

X0 MCU VDD S2 S4 GND S1 GND X1

X Yk Cs YSampling capacitor

X2

Cx

X3

Y0

S3 GND

Y1

Vsns |Vcs| Approximately linear Time t -0.25V Terminal voltage Vyk Time 0.25V

Mutual Capacitance: Touch vs. No Touch?

Now we bring a finger close to electrode This diverts charge from Cx, and so away from CsE-field

CtVcs X YEARTH

So each charge pulse now charges Cs by a smaller amount This means charge builds up in Cs less quickly

No touch

Time

So if each pulse deposits less charge, then Vcs rises slower, so reaches a smaller terminal voltage needs less time to discharge to GND

Vcs

TouchTime

so counter value gets less count change (delta) is proportional to Ct

Delta

Mutual Capacitance vs. Self Capacitance

Self Capacitance: plus Simple electrode design Smaller code size Fewer chip resources used Fairly immune to noise- Especially at frequencies above 1MHz

Mutual Capacitance: plus Above a few channels, needs fewer pins- X by Y needs (X + 2Y + 2) pins - 8 Channels: 4x, 2y = 10 pins - 32 Channels: 8x, 4y = 18 pins

Better moisture tolerance Shorter bursts- Lower power consumption

Self Capacitance: minus Above a few channels, needs more pins- 2 pins per channel - 8 Channels: 16 pins

Predictable timing Touch-sensitive area more localised- Less sensitive to nearby circuitry

Mutual Capacitance: minus More complex electrode design Larger code size More chip resources used Can be more noise-sensitive- Exception New Flooded X design

Longer burst times- Higher power consumption

Timing more variable

Proximity

Proximity achieved via an oversensitive sensor. A few tips to get a proximity field: Self Capacitance- Increase the electrode size to increase the coupling to the hand, i.e. more sensitive. Usually try to have it as big as possible. - Increase the sampling capacitor value to make the sensor more sensitive - Keep sense electrode/components/tracks as far away from ground tracks or other signals as possible; these will desensitise the proximity channel - Always optimise the electrode and layout before increasing the Cs. Increasing the Cs might get the sensing distance, but will always make the sensor more sensitive to external influences.E-field

Mutual Capacitance- Separate X and Y electrodes further apart to increase the Field distance - Increase X electrode size, keeping Y electrode size as small as possible. - Will be difficult with Flooded X layout due to spatial separation of X and Y needed.

Be careful of surrounding environment.- Electrode will be more sensitive to noise. - Power consumption will be higher as the acquisition time will be much longer.

Sliders and Wheels

Linear touch Rotary touch 3 channels High resolution

Sliders and Wheels - Easy scrolling

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

Sliders are popular in personal media devices

Agenda

Common User Interfaces Why Capacitive Touch Sensing? Capacitive Touch Technologies Charge Transfer Technology Self Capacitance Mutual Capacitance Proximity Slider and Rotor Design

Atmels Touch Solutions Buttons/Sliders/Wheels Software Library Touch Screen

Why Choose Atmel?

Atmel Touch Solutions

Atmel Touch ProductsQTouchButton/Slider/Wheel

Touchscreen

Standard Products21 Ready-to-Use devices

QTouch LibraryProgrammable Touch Solutions

Single Touch

Dual Touch 1 to 56 Channels Buttons, Proximity & Sliders QTouch & QMatrix No programming required Limited Flexibility 1 to 64 Channels Buttons, Proximity & Sliders QTouch & QMatrix Highly Flexible

maXTouch

Atmel Touch Solutions

Buttons / Sliders / WheelsQTouch QMatrix QSlide QWheel

q q q q

Self Capacitance For 1 to 10 buttons Simple key shapes Easy to wire

q q q q

Mutual Capacitance Up to 64 keys Water resistant High temperature

q

q q q

Mutual or Self Capacitance Linear touch Rotary touch 3 channels

QTouch Standard Product Roadmap 56 48 32 24 16 QT60486 QT60326 QT60240 QT60248 QT2160 QT60160 QT60168 QT1242 QT1243 QT2165 QT2150 QT1480 QT1481 QT1560

FMEA / EN60730

# of Channels

15 14 11 10 8 7 6 4 1 NOW QT1060 QT1061 QT1040 QT1010 QT1011 QT1012 Q210 QT1070 QT1106

AutomotiveQT1110 QT1111

QT1140

Haptics

Optimized ArchitectureQT1085

Q310 In Development

Q410 Available

Software Library

Free software adding QTouch to your AVR Designs

What is Software Library?

Free software library Available as library include files. Source code is not available

Adds touch capabilities to AVR devices tinyAVR, megaAVR, XmegaA1, and UC3C

Uses any PORT for touch channels Any combination of buttons, wheels and sliders possible

Up to 16 channels of Qtouch, and 64 channels of Qmatrix Precompiled linkable libraries for selected AVR devices More devices to be supported in near future Updates can be downloaded from Touch Library website

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Software Library: Advantages

Free access to industry-leading QTouch technology Available on Atmel website -- http://www.atmel.com/touchlib Users need to agree to a Limited License Agreement Use with Atmel microcontroller No redistribution except in integrated product Full details are stated in the License Agreement

Add touch capabilities without need for external device Single-chip solution

Precompiled and verified to work on supported devices Well-defined API allowing full control and customization Complete development ecosystem

April 10

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QTouch Library Device SupportARM

All devices

All devices All devices All devices

Cortex M3

Select devices

Select devices

Select devices

UC3L

Q409

For a complete list of supported devices: QTouch Library User Guide www.atmel.com/QTouchlib New devices added throughout 2010 ARM7 support in Q210 ARM9 support in Q410

Touch library, only advantages ? Touch library Available for nearly all AVR, XMEGA, AVR32 and combinations out of AVR (such as LIN/AVR) Single controller application support Flexible solution on parameters Automotive parts available Critical timing may generate a bottleneck Cost efficient solution (sw is free of charge)

Fixed function device Ready out of the box solution Easy to implement Limited number of parameters to change Nearly no automotive qualified devices available No issues when you have time critical applications ATMEL proofed solution

Fixed SPI function

Host

Touch library

AVR

Software Library: Development Tools

Atmel Touch Library Fully Documented

Evaluation Kits ATAVRTS2080A for ATmega88 ATAVRTS2080B for ATtiny88 Software and documentation must be downloaded

Free AVR QTouch Studio Front-end for all Evaluation Kits Download from www.atmel.com/touchlib

Complete tool chain available now!April 10 32

TouchscreenHow to build a touch screen

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Atmels Touch In Vending Machine

http://www.youtube.com/watch?v=2wc2lX6zF5c Customer needs: Vandalism safe and waterproof, touch iUI 3.4" OLED Display 480x272

Customer benefits:Atmel System Solution SAM9261 + QT60160 Easy and fast software development .Net Micro Framework (available on SAM9261) Using .NET made using the QT a snap (200 lines code size driver done in a day ) ClickTouch ITO : very experienced with QT and ITO technology

ApplicationTWI

Vending Machine iUI 4 mm glass QT60160RGB

SAM9261

ITO OLED

Agenda

Common User Interfaces Why Capacitive Touch Sensing? Capacitive Touch Technologies Charge Transfer Technology Self Capacitance Mutual Capacitance Proximity Slider and Rotor Design

Atmels Touch Solutions Buttons/Sliders/Wheels Software Library Touch Screen

Why Choose Atmel?

Why Choose Atmel?

Technological AdvantagesAdjacent Key Suppression (AKS) Failure mode detection (FMEA) Automatic and frequent calibration Ultra low power consumption Most devices support 1.8V operation Works very well in inductive systems Single layer PCB

Reliability Advantages Tolerates contamination Works in presence of moisture Automatically compensates for temperature, humidity, voltage changes, and aging of components No production calibration needed

Ease of Design Breadth of product range Rapid user designs easy to prototype with an evaluation board Choice of Fixed Function devices or Software Library support on most AVR microcontrollers Various communication options