Capacitive Touch Based User Interfaces and Hardware-based Solutions

Transcription

1 Capacitive Touch Based User Interfaces and Hardware-based Solutions Renesas Electronics America Inc.

2 Renesas Technology & Solution Portfolio 2

3 Microcontroller and Microprocessor Line-up bit 8/16-bit 1200 DMIPS, Superscalar Automotive & Industrial, 65nm 600µA/MHz, 1.5µA standby 500 DMIPS, Low Power Automotive & Industrial, 90nm 600µA/MHz, 1.5µA standby 165 DMIPS, FPU, DSC Industrial, 90nm 242µA/MHz, 0.2µA standby 25 DMIPS, Low Power Industrial & Automotive, 150nm 190µA/MHz, 0.3µA standby 10 DMIPS, Capacitive Touch Wide Industrial Format & LCDs Automotive, 130nm 350µA/MHz, 1µA standby 1200 DMIPS, Performance Automotive, 40nm 500µA/MHz, 35µA deep standby 165 DMIPS, FPU, DSC Industrial, 40nm 242µA/MHz, 0.2µA standby Embedded Security, ASSP Industrial, 90nm 1mA/MHz, 100µA standby 44 DMIPS, True Low Power Industrial & Automotive, 130nm 144µA/MHz, 0.2µA standby 3

4 Enabling The Smart Society Challenge: Embedded designs are increasingly being incorporated in new, innovated interfaces. How can the engineer keep up with the increased demand for users desires for enhanced user interfaces. Solution: Let s investigate one of those highly desired interfaces, capacitive touch! 4

5 Agenda Market Trend Typical System Configurations Design Considerations Renesas Solution 5

6 Market Trend 6

7 Expansion of Capacitive Touch Key Interfaces Adoption of technology is happening Applications Adopted by Consumer Electronics Proliferation across all segments High End Equipment 1990 s 2000 s 2010 s and beyond 7

8 Why Use Capacitive Touch Interfaces Audience: Why would you use a touch interface? 8

9 Some Examples Aesthetics Reliability Maintenance Interface Reuse 9

10 Typical System Configurations 10

11 Touch Channel vs. Key vs. PCB Electrode 1 touch channel does not necessarily mean 1 key Touch Controller Ch0 Ch1 Ch2 Ch3 Ch4 Ch5 Ch6 Ch7.. Matrix Configuration. Key1 Key2 Key3 Key4 Key5 Key6 Key7 Key8 Key9 Direct Key Configuration F2 11

12 Configuration Example (Touch Sensor IC) Dedicated IC for touch sensing Single-chip reduces BOM cost Only Touch Sensing Single-chip GPIO/ PWM GPIO/ PWM 2 2 System + Touch Controller Serial I/F Audible Audible Feedback Feedback (Buzzer) (Buzzer) Touch Sensor Analog IC Visual Feedback (LED/backlight) Visual Feedback (LED/backlight) Analog

13 Why Use Capacitive Touch Interfaces Audience: Can you name some interfaces that would benefit from capacitive touch interfaces? Why? 15

14 Examples of Focused Applications Application Touch Functions System Functions Security Keypad 19 keys LEDs, buzzer, communication Blood Pressure monitor 9 keys Buzzer, communication Printer 16 keys LEDs, buzzer, communication Oven Over 25 keys LEDs, buzzer, communication 16

15 Design Considerations 17

16 Typical Touch Key Design Flow Specify touch requirements (ex: type of touch I/F, # of keys, overlay), and other system constraints including mechanical Evaluate options with actual hardware (ex: Kit) select best fit solution Design per vendor s recommendations (including PCB layout, noise countermeasures) Initial testing and tuning of hardware + software (including noise filtering). If performance not met go back to step #3 5 Final tuning in full system Mass Production 18

17 Reliable Capacitive-based Touch Key Detection All solutions based on same concept: measurement of change in capacitance Must maximize signal-to-noise ratio System-level design considerations, not just a sensor IC Noise Signal Noise 19

18 Touch Design Considerations (Hardware) Electrical Mechanical Flat Overlay Electrode Shape and Size Layout Touch Controller d2 d1 d3 d Other: Grounding pattern, ESD Power supply stability LED or PWM signal Other: Non-Flat Overlay Material, thickness 20

19 Touch Design Considerations (Firmware) Measurement Scanning should not be interrupted Need multiple charging/discharging and measurements for good accuracy Tuning and Debugging Software tuning to maximize SNR Real-time monitoring while touch detection Source code (APP + Touch) for optimization Application-Level Touch Functions Multi-touch, wheel/slider decoding, water detection/suppression: application-specific Noise Filtering Filtering may be required (as postprocessing) depending on system s electrical noise environment 21

20 Renesas Touch Key Solution 22

21 R8C/3xT Detection Mechanism VCHxA Cr Rc Cc SCU handles all the sequencing and timing CHxA CHxB CHxC Vth Counter CH0 Rr Cx Sensor Control Unit (SCU) Detection: Connect one sensor channel to CHxA using internal MUX Charge Cc by driving CHxC High Switch CHxC to Hi-Z mode Discharge Cc through Rc by driving CHxB Low Switch CHxB to Hi-Z mode Check the logic level of ChxA If logic level is still high repeat steps 4,5 and 6 until the logic level goes low Implementation in R8C/3xT Cx (touch) > Cx (no touch) VCHxA = Cr Cr + Cx Vc 23

22 Simplified Hardware Circuit Major components Charge Circuit Circuit Control Capacitance Detection Touch Electrode 24

23 Circuit Operation Repeat discharge and re-distribution Test if Vct below Vref No = Count channel up Yes = Cycle complete 25

24 Touch Analog to Digital Tracking counts vs. time Counts Time 26

25 Sensor Control Unit (SCU) 1 2 Control, Status, and Error Management 3 Measurement and Sequencing/Scanning 4 Noise Countermeasure Data transfer Trigger Signal Clock 1 Trigger control block Count source control block Status counter (5-bits) Status decoder Sensor Control Unit (SCU) Timing variable counter Channel control counter 2 1 Channel control block 1 Channel Selection Secondary counter Primary counter 3 2 Measurement block 2 4 Sensor DMA Touch Signal To RAM Data buffer 4 4 Transfer request control block DTC Request 27

26 R8C T-SCU CPU Utilization R8C/3xT SCU performs touch scanning autonomously In software solution, CPU is utilized 100% Softwarebased solution CPU CPU Active (Touch Scanning) CPU Active (System Functions) R8C/3xT Option A CPU SCU System Functions Scanning + Data Transfer CPU Active (Touch Post Processing) R8C/3xT Option B CPU SCU CLK Not Operating Scanning + Data Transfer Less than 15% of total CPU time (20MHz) 28

27 Single-chip MCU for Touch + System Control Renesas Touch MCU (R8C/3xT) No External ICs Step-down converter IC EEPROM IC Crystal CPU 1.8V 5.5V Data Flash 40MHz Osc. LVD / POR Flash RAM COMM A/D GP Timers SCU CH0 CH1 CH2... CH33 CH34 CH35 Wheel Reset IC WDT IC Watchdog 20mA Ports Debug CHxC CHxB CHxA Wide range of peripherals for Application Use Cc Rc Cr Only 2C s + 1R for touch 29

28 R8C/3xT Low Power Consumption Average Current = ~16 µa for 1 channel Clock Source Low-speed OCO High-speed OCO High-speed OCO Peripheral Clock 125kHz 5MHz 5MHz CPU State Stop Stop Active Code Execution N/A N/A Yes State Current * 8.3 µa 610 µa (per ch) 2 ma Time 100 ms 340 µs 200 µs * Typical value based on specific test platform 30

29 Optimized Software Architecture Complete Touch Sensor API as source code User Application Application Functional Noise Rejection (Debounce, Wipedown) Functional Implementation Matrix Decoder Wheel Decoder Auto Calibration Switch Decoder Sensor Touch Decision (Binary) Drift Compensation Sensor Reference and Threshold Low Level Filter Hardware Layer SCU Driver 31

30 Advanced Tuning Tools Intuitive GUI Measurement Parameter Setting Circuit Modeling 32

31 Benefits of Renesas Capacitive Touch Solution Hardware-Assisted Touch <15% of CPU utilization Built-in noise countermeasures Touch sensing in standby High Integration Full peripheral functions for system control Reduced system cost Easy Debugging Integrated on-chip debug unit Advanced touch tuning tool (Touch Workbench) Extensive Support Complete evaluation system Application Notes 33

32 Renesas Touch MCU (R8C/3xT) Line-up 128 KB R5F213NCT R5F2136CS R5F2138CS TSCU 96 KB R5F213NAT R5F2136AS R5F2138AS SCU 64 KB R5F213N8T R5F21368S R5F21388S 48 KB R5F213N7T 32 KB R5F21336T R5F213J6T 24 KB R5F21335T R5F213J5T 16 KB R5F21334T R5F213J4T 32 7x7 QFP 40 5x5 QFN 48 3x3 WPP 64 10x10 QFP 14x14 QFP 80 12x12 QFP Touch Channels * * 1 Touch channel = 1 key (no matrix configuration) 34

33 Self-contained Touch Evaluation System Evaluation System Features R8C/36T-A (64-pin) Keys, Wheel, Slider LED Display Ambient light sensor Buzzer Current consumption measurement E1 Debug Emulator CD containing: Touch API and sample application code Workbench Tool Free 64KB C Compiler Documentation E1 Debugger Keys Wheel Slider Ordering Information: P/N: YR8C36TKIT

34 Online Resources for Touch MCU Solutions Home Page Product & Feature Information Application Notes Software Download 36

35 Questions? 37

36 Enabling The Smart Society Challenge: Embedded designs are increasingly being incorporated in new, innovated interfaces. How can the engineer keep up with the increased demand for users desires for enhanced user interfaces. Solution: Let s investigate one of those highly desired interfaces, capacitive touch! Do you agree that we accomplished the above statement? 38

37 Renesas Electronics America Inc.