SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING KEY PRODUCT FEATURES GENERAL DESCRIPTION • The SX8677 and SX8678 belong to a family of high performance haptics enabled multitouch 4/5-wire resistive touch screen controller with proximity detection, optimized for hand held applications such as mobile phones, portable music players, game machines, point-of-sales terminal and other consumer and industrial applications. They feature a wide input supply range from 2.3V to 3.6V. • The controller computes touch screen X-Y coordinates and touch pressure with a precision, low power 12-bit analog-digital converter. On-chip data averaging processing algorithms can be activated to reduce host activity and suppress system noise. The processing core features low power modes which intelligently minimize current in operation as well as in automatic shut-down. • Low Voltage Operation 2.3V to 3.6V Supply Integrated Low Drop Out (LDO) Regulator Low Power Consumption [email protected] 8ksps (ESR) 0.4uA Shut-Down Current 4/5-Wire Touchscreen Interface Precision, Ratiometric 12-bit ADC Up to 5000 (X-Y) coordinates/second (c/s) Programmable Digital Filtering/Averaging Touch Pressure Measurement (4-Wire) Programmable Operating Mode (Manual, Pen Detect, Pen Trigger) Capacitive Proximity Sensing (SX8677) No Additional Components Required Uses Resistive Touchscreen or a Simple Conductive Area as the Sensor >5 cm Detection Distance 8uA @ 200ms Scan Period Fully Programmable (Sensitivity, etc) Haptics Driver for LRA and ERM (SX8677/78) Supports Immersion TouchSense® 3000 haptic control software Haptics Waveform Generation Control (I2C or PWM Input) Short Circuit Protection Early Warning and Over-Temperature Monitoring and Protection 400kHz I2C Serial Interface Several Host Operating Modes Available Maskable Interrupt Output (NIRQ) Real-time Events Monitoring (AUX1-3) Polling (I2C) Hardware, Software, and Power-On Reset -40°C to +85°C Operating Temperature Range 15kV HBM & IEC ESD Protection Small Footprint Packages Pb & Halogen Free, RoHS/WEEE compliant • Multitouch feature enables detection of 2 fingers on the touchscreen and several gestures like rotation and pinch/stretch. A capacitive proximity detection circuit has been integrated into the SX8677 to enable host controlled power management for battery applications. Proximity detection above 5 cm is possible using either the resistive touch screen as the sensor or with a single conductive plate, with communication to the host via the serial interface. • The SX8677 and SX8678 also integrate a haptics motor driver for Linear Resonant Actuator (LRA) and Eccentric Rotating Mass (ERM) micro motors with up to 250mA drive current. Haptics control can be performed using either an external PWM signal or the I2C serial interface, providing simple host interfacing and minimizing its I/O requirement. The SX8677/78 supports Immersion TouchSense® 3000 haptic control software for high quality touch feedback. • • Integrated very high ESD protection, of up to ±15kV on display inputs not only saves cost and board area, but also increases application reliability. • • • • • The three devices have an ambient operating temperature range of -40°C to +85°C, and are offere d in both a 4mm x 4mm, 20-lead QFN package and 2.07mm x 2.07mm 19-lead CSP package for spaceconscious applications. TYPICAL APPLICATIONS • • • • • M Game Machines, Portable Music Players Mobile Phones DSC, DVR, Phones POS/POI Terminals Touch-Screen Monitors HAPTICS DRIVER NRST SX8677 ORDERING INFORMATION Part Number SX8677IWLTRT SX8677ICSTRT SX8678IWLTRT SX8678ICSTRT SX8674EVK th Rev 1 – 25 July 2011 Package QFN-20 WLCSP-19 QFN-20 WLCSP-19 Evaluation Kit I2C NIRQ Marking Host Controller MULTITOUCH CONTROL RNT2 RP9X - PROXIMITY SENSING 1 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Table of Contents GENERAL DESCRIPTION ..................................................................................................................... 1 TYPICAL APPLICATIONS ..................................................................................................................... 1 ORDERING INFORMATION................................................................................................................... 1 KEY PRODUCT FEATURES.................................................................................................................. 1 1 GENERAL DESCRIPTION ............................................................................................................ 4 1.1 Marking Information 1.1.1 SX8677 1.1.2 SX8678 1.2 Pin Diagrams 1.2.1 QFN Package 1.2.2 CSP Package 1.3 Pin Description 1.4 Block Diagram 2 4 4 4 5 5 5 6 6 ELECTRICAL CHARACTERISTICS ............................................................................................... 8 2.1 2.2 2.3 Absolute Maximum Ratings Thermal Characteristics Electrical Specifications 8 8 8 3 TYPICAL OPERATING CHARACTERISTICS ............................................................................... 11 4 TOUCHSCREEN INTERFACE..................................................................................................... 12 4.1 4.2 Introduction Coordinates Measurement 4.2.1 4-wire Touchscreen 4.2.2 5-wire Touchscreen 4.3 Pressure Measurement (4-wire only) 4.3.1 Bias Time (POWDLY) 4.4 Pen Detection 4.5 Multitouch Measurement (4-wire only) 4.6 Digital Processing 4.7 Host Operation 4.7.1 Overview 4.7.2 Manual Mode (MAN) 4.7.3 Pen Detect Mode (PENDET) 4.7.4 Pen Trigger Mode (PENTRG) 4.7.5 Maximum Throughput vs. TOUCHRATE setting 5 12 13 13 14 14 15 15 16 17 18 18 18 20 20 21 PROXIMITY SENSING INTERFACE (SX8677) ............................................................................ 23 5.1 5.2 Introduction Analog Front-End (AFE) 5.2.1 Capacitive Sensing Basics 5.2.2 AFE Block Diagram 5.2.3 Capacitance-to-Voltage Conversion (C-to-V) 5.2.4 Shield Control 5.2.5 Offset Compensation 5.2.6 Analog-to-Digital Conversion (ADC) 5.3 Digital Processing 5.3.1 Overview 5.3.2 PROXRAW Update 5.3.3 PROXUSEFUL Update 5.3.4 PROXAVG Update th Rev 1 – 25 July 2011 2 23 24 24 25 26 26 26 27 27 27 28 29 30 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.3.5 PROXDIFF Update 5.3.6 PROXSTAT Update 5.4 Host Operation 5.4.1 General Description 5.4.2 Proximity Sensing vs Touch Operations 5.4.3 Minimum Scan Period (i.e. PROXSCANPERIOD) 6 32 32 33 33 33 35 HAPTICS INTERFACE (SX8677/78) .......................................................................................... 36 6.1 6.2 Introduction ERM Load 6.2.1 Introduction 6.2.2 PWM Mode 6.2.3 I2C Mode 6.3 LRA Load 6.3.1 Introduction 6.3.2 PWM Mode 6.3.3 I2C Mode 6.4 Short-Circuit Protection 36 36 36 37 37 37 37 38 38 38 7 TEMPERATURE SENSOR.......................................................................................................... 39 8 INTERRUPT (NIRQ) .................................................................................................................. 40 8.1 8.2 Introduction Registers Overview 8.2.1 RegIrqMsk 8.2.2 RegIrqSrc 8.2.3 RegStat 8.3 Host Procedure 40 40 40 40 40 40 9 AUXILIARY PINS (AUX1/AUX2/AUX3)...................................................................................... 41 10 RESET ...................................................................................................................................... 42 10.1 10.2 10.3 11 Hardware (POR and NRST) Software (RegReset) ESD Event (RESETSTAT) 42 42 42 I2C INTERFACE ........................................................................................................................ 43 11.1 11.2 11.3 11.4 11.5 11.6 Introduction I2C Address Write Register Read Register Write Command (Touchscreen Interface) Read Channel (Touchscreen Interface) 43 43 43 44 44 45 12 REGISTERS DETAILED DESCRIPTION ...................................................................................... 47 13 APPLICATION INFORMATION ................................................................................................... 59 13.1 Typical Application Circuit 13.2 External Components Recommended Values 13.3 Multitouch Gestures 13.3.1 Pinch/Stretch 13.3.2 Rotate 14 59 59 59 59 60 PACKAGING INFORMATION ..................................................................................................... 61 14.1 14.2 QFN Package CSP Package th Rev 1 – 25 July 2011 61 62 3 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 1 GENERAL DESCRIPTION 1.1 1.1.1 Marking Information SX8677 Figure 1 – Marking Information – QFN(left) – CSP(right) 1.1.2 SX8678 Figure 2 – Marking Information – QFN(left) – CSP(right) th Rev 1 – 25 July 2011 4 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 1.2 1.2.1 Pin Diagrams QFN Package Figure 3 – Pin Diagram – QFN 1.2.2 CSP Package Figure 4 – Pin Diagram - CSP th Rev 1 – 25 July 2011 5 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 1.3 Pin Description Name VDD GND VREG MVDD MGND MOUTP MOUTN MIN Type P P P P P AO AO DI X+/BR A Y+/TR A X-/TL A Y-/BL A AUX1/WIPER D/A AUX2 AUX3 ADDR SCL SDA NIRQ NRST D/A D/A DI DI DIO DO DI Description Main Power Supply Main Ground Internal Regulator Output (must be connected to an external capacitor; see §13) Haptics Motor Power Supply Haptics Motor Ground (must be electrically connected to GND) Haptics Motor Positive Drive Haptics Motor Negative Drive Haptics Motor PWM/Clock Input • 4-wire Touchscreen : X+ Electrode • 5-wire Touchscreen : Bottom Right (BR) Electrode • 4-wire Touchscreen : Y+ Electrode • 5-wire Touchscreen : Top Right (TR) Electrode • 4-wire Touchscreen : X- Electrode • 5-wire Touchscreen : Top Left (TL) Electrode • 4-wire Touchscreen : Y- Electrode • 5-wire Touchscreen : Bottom Left (BL) Electrode • 4-wire Touchscreen : First Programmable Auxiliary Function (see §9) • 5-wire Touchscreen : WIPER Electrode Second Programmable Auxiliary Function (see §9) Third Programmable Auxiliary Function (see §9) I2C Address Selection (QFN only, internally connected to GND on CSP) I2C Clock Input I2C Data Input/Output Interrupt Output (active low) Reset Input (active low) A/D/I/O/P: Analog/Digital/Power/Input/Output Table 1 – Pin Description 1.4 Block Diagram Figure 5 – SX8677 Block Diagram th Rev 1 – 25 July 2011 6 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 6 – SX8678 Block Diagram th Rev 1 – 25 July 2011 7 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 2 ELECTRICAL CHARACTERISTICS 2.1 Absolute Maximum Ratings Stress above the limits listed in the following table may cause permanent failure. Exposure to absolute ratings for extended time periods may affect device reliability. The limiting values are in accordance with the Absolute Maximum Rating System (IEC 134). All voltages are referenced to ground (GND). Conditions Symbol Description Min Max Unit VABS Voltage applied on any pin VESDHBM Electrostatic handling Human Body Model (HBM) VESDCDM VESDMM VESDCD TAMB TJUN TSTOR ILAT - 0.5 Electrostatic handling Charged Device Model (CDM) Electrostatic handling Machine Model (MM) Electrostatic handling Contact Discharge (CD) Operating ambient temperature Operating junction temperature Storage temperature (3) Latch-up current X+/BR, Y+/TR, X-/TL, Y-/BL, VDD, MVDD Other pins X+/BR, Y+/TR, X-/TL, Y-/BL, VDD, MVDD Other pins X+/BR, Y+/TR, X-/TL, Y-/BL, VDD, MVDD Other pins X+/BR, Y+/TR, X-/TL, Y-/BL, VDD, MVDD 3.9 (1) V (2) +/-15 , +/-8 kV (2) +/-8 +/-1 kV +/-1 +/-250 V +/-250 +/-15 kV -40 +85 -40 +125 -55 +150 +/-100 °C °C °C mA (1) Tested to TLP (10A) (2) Tested to JEDEC standard JESD22-A114 (3) Tested to JEDEC standard JESD78 Table 2 - Absolute Maximum Ratings 2.2 Thermal Characteristics Conditions Description Thermal Resistance Junction – Ambient QFN package Thermal Resistance Junction – Ambient WLCSP package Table 3 – Thermal Characteristics Symbol θJAQ θJAW Min Max Unit - 30.5 °C/W - 29 °C/W 2.3 Electrical Specifications Table below applies to full supply voltage and temperature range, unless otherwise specified. Typical values are given for TA = +25°C, VDD=VDDM=3.3V. Symbol Description Conditions Min Typ. Max Unit Supply VDD Main supply voltage 2.3 3.6 V OFF uA IDD Main supply current 0.4 0.75 (MAN mode, no command, HAPT OFF) WAIT (PENDET/TRG mode, pen up, PROX OFF, HAPT OFF) - 1.7 - - 30 - - 120 160 TOUCH1 (PENTRG mode, pen down, X+Y, RATE=4kcps, Nfilt=1, POWDLY=0.5us, touchscreen current excluded, HAPT OFF, VDD=2.3V) TOUCH2 (PENTRG mode, pen down, X+Y, RATE=3kcps, Nfilt=7, POWDLY=0.5us, touchscreen current excluded, HAPT OFF) th Rev 1 – 25 July 2011 8 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Symbol Description Conditions PROX (PENDET/TRG mode, pen up, TOUCHRATE=80cps, PROX ON, SCANPERIOD=200ms, HIGHIM=ON, SENSITIVITY=Max, FREQ=150kHz, BOOST=OFF, HAPT OFF) Min Typ. Max Unit - 8 20 - 115 145 VDD - 0.01 3.6 1 V µA - 6 10 µA HAPT (MAN mode, no command, LRA-PWM mode, MIN= 44.8kHz/50%, GAIN = Max, BW = 100, MOUTP/N floating, Squelch=011) MVDD Haptics supply voltage OFF SQUELCH MIDD Haptics supply current (LRA-PWM mode, MIN= 44.8kHz/50%, GAIN = Max, BW = 100, MOUTP/N floating, Squelch=011) Digital I/Os (ADDR, SCL, SDA, NRST, NIRQ, AUX1, AUX2, AUX3, MIN) SCL, SDA, NRST 0.8*VDD VIH High level input voltage Other pins 0.8*VDD VIL Low level input voltage -0.3 ILEAK Input leakage current -1 CI Input capacitance VOH High level output voltage IOH = 4mA 0.8*VDD VOL Low level output voltage IOL = 4mA VPULL External pull-up voltage SCL, SDA, NRST, NIRQ Haptics Interface Maximum drive current IDRV MVDD = 3.6V (MOUTP/MOUTN) VOFF Output squelch differential error (from 0V ideal) VERR Output differential error (from 1.135V ideal) VDRV Drive voltage (MOUTP/MOUTN) VDROP Drop voltage (MOUTP/MOUTN) ISHORT Short-circuit detection current Motor input (MIN) frequency in I2C mode FMINC Motor input (MIN) frequency in PWM mode FMINP Motor input (MIN) duty cycle in PWM mode TWRNG Warning temperature TALRM Alarm temperature Touchscreen Interface ARES ADC resolution AOFF ADC offset AGE ADC gain error ADNL ADC differential non-linearity AINL ADC integral non-linearity RBIAS Biasing resistance Proximity Sensing Interface External capacitance to be CDC compensated tPROX Scan period (reaction time) LRA or ERM, PWM or I2C, AmplitudeCode within squelch range, GAIN = Max, BW = 100, MOUTP/N floating, Squelch=011 LRA or ERM, I2C, AmplitudeCode = +127 (Max) GAIN = Min, BW = 100, MOUTP/N floating th 250 3.6 V VDD+0.2 0.8 V 1 µA pF V 0.4 V 3.6 V - mA (1) mV 0 0 125 0 125 (2) (2) mV From MVDD/MGND, @250mA Measured @MIDD - - VDDM V - - 150 mV - 300 - mA 40-60% duty cycle - - 50 MHz HAPTRANGE = 0 12.8 - 25.6 kHz HAPTRANGE = 1 25.6 - 51.2 kHz 2 - 98 % - 120 155 - °C 12 - ±1 0.5 ±1 ± 1.5 5 - LSB - - - 300 pF Programmable - 200 - ms DCMIN Rev 1 – 25 July 2011 (1) 0 5 - Junction temperature At full scale 9 bits Ω www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Symbol Description Reset VPOR Power-On-Reset voltage tRESET Reset time after POR tPULSE Reset pulse from host uC I2C Interface fSCL Cb SCL clock frequency Hold time (repeated) START condition LOW period of the SCL clock HIGH period of the SCL clock Set-up time for a repeated START condition Data hold time Data set-up time Rise time of both SDA and SCL Fall time of both SDA and SCL Set-up time for STOP condition Bus free time between a STOP and START condition Capacitive load for each bus line tSP Pulse width of spikes suppressed by the input filter tHD;STA tLOW tHIGH tSU;STA tHD;DAT tSU;DAT tr tf tSU;STO tBUF Conditions Min Typ. Max Unit Cf. §10 Cf. §10 Cf. §10 1 1.3 - 1 - V ms us - - - 400 kHz - 0.6 - - µs - 1.3 0.6 - - µs µs - 0.6 - - µs - 0 100 20+0.1Cb 20+0.1Cb 0.6 - 300 300 - µs ns ns ns µs - 1.3 - - µs Up to 0.3xVDD from GND, down to 0.7xVDD from VDD - - 400 pF 50 - - ns - 32 1.8 - kHz MHz Miscellaneous FOSCL Low frequency internal oscillator FOSCH High frequency internal oscillator (1) (2) - Guaranteed by design. PWM mode can introduce an additional error of 2.5% of full scale. Table 4 – Electrical Specifications th Rev 1 – 25 July 2011 10 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 3 TYPICAL OPERATING CHARACTERISTICS Conditions as defined in §2.3, TA = +25°C, VDD=VDDM=3.3V unless otherwise specified. IDD_WAIT vs VDD vs TOUCHRATE IDD_OFF vs VDD vs TEMP 4.00E-07 8 3.80E-07 7 3.60E-07 6 3.40E-07 5 10cps IDD(uA) IDD(A) 3.20E-07 25°C 3.00E-07 85°C -40°C 80cps 4 2000cps 5000cps 2.80E-07 3 2.60E-07 2 2.40E-07 1 2.20E-07 0 2.00E-07 2.3 2.3 2.5 2.7 2.9 3.1 3.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.5 VDD(V) VDD(V) IDD_HAPT vs VDD vs TEMP IDD_PROX vs SCANPERIOD vs SENSITIVITY 0.0002 80 0.00019 70 0.00018 60 0.00017 0.00016 0(Min) 40 IDD(A) IDD_PROX(uA) 50 5 7(Max) 25°C 0.00015 85°C -40°C 0.00014 30 0.00013 20 0.00012 10 0.00011 0 0.0001 0 100 200 300 400 500 600 700 800 2.3 2.5 2.7 SCANPERIOD(m s) 2.9 3.1 3.3 3.5 VDD(V) MIDD_SQUELCH vs MVDD vs TEMP MIDD_OFF vs MVDD vs TEMP 1.00E-05 5.00E-08 4.50E-08 9.00E-06 4.00E-08 3.50E-08 8.00E-06 25°C 2.50E-08 25°C IDD(A) MIDD(A) 3.00E-08 85°C -40°C 85°C -40°C 7.00E-06 2.00E-08 1.50E-08 6.00E-06 1.00E-08 5.00E-09 5.00E-06 0.00E+00 2.3 2.5 2.7 2.9 3.1 3.3 2.3 3.5 2.5 2.7 2.9 3.1 3.3 3.5 MVDD(V) MVDD(V) VERR vs GAIN vs MVDD 0.08 0.07 0.06 VOFF(V) 2.3V 3.3V 0.05 3.6V 0.04 0.03 0.02 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 GAIN th Rev 1 – 25 July 2011 11 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 4 4.1 TOUCHSCREEN INTERFACE Introduction The purpose of the touchscreen interface is to measure and extract touch information like coordinates and pressure. This is done in two steps, first an ADC measures the analog signal coming from the screen, and then digital processing is performed to consolidate the data. As illustrated below the chip’s touchscreen interface is compatible with both 4-wire and 5-wire touchscreens. Touchscreen type is defined by parameter TSTYPE. Figure 7 – Touchscreen Interface Overview A 4-wire resistive touch screen consists in two (resistive) conductive sheets separated by an insulator when not pressed. Each sheet is connected through 2 electrodes at the border of the sheet. When a pressure is applied on the top sheet, a connection with the lower sheet is established. Figure 8 – 4-wire Touchscreen A 5-wire resistive touch screen consists in two (resistive) conductive sheets separated by an insulator when not pressed. 4 electrodes are connected on the 4 corners of the bottom conductive sheet. They are referred as Top Left (TL), Top Right (TR), Bottom Left (BL) and Bottom Right (BR). The fifth wire (WIPER) is used for sensing the top sheet voltage. When a pressure is applied on the top sheet, a connection with the lower sheet is established. th Rev 1 – 25 July 2011 12 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Higher reliability and better endurance are the advantages of 5-wire touchscreens but they do not allow pressure measurement Figure 9 – 5-wire Touchscreen 4.2 Coordinates Measurement 4-wire Touchscreen 4.2.1 The electrode plates are internally connected through terminals X+, X- and Y+, Y- to an analog to digital converter (ADC) and a reference voltage (Vref). The resistance between the terminals X+ and X- is defined by Rxtot. Rxtot will be split in 2 resistors, R1 and R2, in case the screen is touched. Similarly, the resistance between the terminals Y+ and Y- is represented by R3 and R4. The connection between the top and bottom sheet is represented by the touch resistance (RT). In order to measure the Y coordinate, the top resistive sheet (Y) is biased with a voltage source (Vref). Resistors R3 and R4 determine a voltage divider proportional to the Y position of the contact point. Since the converter has a high input impedance, no current flows through R1 (and RT) so that the voltage X+ at the converter input is given by the voltage divider created by R3 and R4. The X coordinate is measured in a similar fashion with the bottom resistive sheet (X) biased to create a voltage divider by R1 and R2, while the voltage on the top sheet is measured through R3. The resistance RT is the resistance obtained when a pressure is applied on the screen. RT is created by the contact area of the X and Y resistive sheet and varies with the applied pressure. Figure 10 – 4-wire Touchscreen Coordinates Measurement The X and Y positions output by the ADC correspond to the formulas below: R2 Xpos = 4095 ⋅ --------------------R1 + R2 R4 Y pos = 4095 ⋅ -------------------R3 + R4 12 4095 corresponds to the max output value of the ADC (12 bits => 2 – 1). For example, a touch in the center of the screen will output (Xpos, Ypos) = ~(2048, 2048) th Rev 1 – 25 July 2011 13 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 4.2.2 5-wire Touchscreen 5-wire touchscreen coordinates measurement is performed similarly by biasing opposite corner pairs in either X or Y directions on the lower panel, and converting the voltage appearing on the wiper panel with the ADC. Figure 11 – 5-wire Touchscreen Coordinates Measurement The X and Y positions output by the ADC correspond to the formulas below: R2 Xpos = 4095 ⋅ --------------------R1 + R2 R4 Y pos = 4095 ⋅ -------------------R3 + R4 12 4095 corresponds to the max output value of the ADC (12 bits => 2 – 1). For example, a touch in the center of the screen will output (Xpos, Ypos) = ~(2048, 2048) 4.3 Pressure Measurement (4-wire only) The pressure measurement consists in extracting the touch resistance RT via two additional setups z1 and z2 illustrated below. The smaller RT, the more common touched surface there is between top and bottom plates and hence the more “pressure” there is by the user. Figure 12 – Pressure Measurement The z1 and z2 values output by the ADC correspond to the formulas below: R4 z1 = 4095 ⋅ --------------------------------R1 + R4 + R T R4 +---------------Rt z2 = 4095 ⋅ ----------------R1 + R4 + R T The X and Y total sheet resistance (Rxtot = R1+R2, Rytot = R3+R4) are known from the touch screen supplier. R4 is proportional to the Y coordinate and its value is given by the total Y plate resistance Rytot multiplied by the fraction of the Y position over the full coordinate range. th Rev 1 – 25 July 2011 14 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Re-arranging z1 and z2 gives: Rxtot = R1 + R2 Rytot = R3 + R4 Ypos R4 = Rytot ⋅ ------------4095 z2 z2 R T = R4 ⋅ ------ – 1 z1 This finally results in: z2- – 1 R T = Rytot ⋅ Ypos ------------- ⋅ ----4095 z1 The touch resistance calculation above hence requires three channel measurements (Ypos, z2 and z1) and one specification data (Rytot). An alternative calculation method is using Xpos, Ypos, one z channel and both Rxtot and Rytot as shown in the next calculations. R1 is inversely proportional to the X coordinate: Xpos R1 = Rxtot ⋅ 1 – ------------4095 Substituting R1 and R4 into z1 and rearranging terms gives: Rytot ⋅ Ypos 4095 Xpos RT = -------------------------------- ⋅ ------------ – 1 – Rxtot ⋅ 1 – ------------4095 z1 4095 Please note that the chip only outputs z1, z2, etc. The calculation of RT itself with the formulas above must be performed by the host. 4.3.1 Bias Time (POWDLY) In order to perform correct measurements, some time must be given for the touch screen to reach a proper Vref bias level before the conversion is actually performed. It is a function of the PCB trace resistance connecting the chip to the touchscreen and also the capacitance of the touchscreen. If tau is this RC time constant, then POWDLY duration must be programmed to 10 tau to reach 12 bits accuracy. Adding a capacitor from the touch screen electrodes to ground may also be used to minimize external noise (if the touchscreen is used as the proximity sensor, make sure you do not exceed the maximum capacitive load for required for proper proximity sensing operation). The low-pass filter created with the capacitor may increase settling time requirement. Therefore, POWDLY can be used to stretch the acquisition period and delay conversion appropriately. POWDLY can be estimated by the following formula: PowD ly = 10 × Rtouch × Ctouch 4.4 Pen Detection The pen detection circuitry is used both to detect a user action and generate an interrupt or start an acquisition in PENDET and PENTRG mode respectively. Doing pen detection prior to conversion avoids feeding the host with dummy data and saves power. Pen detection is also used to disable and resume proximity sensing. For more details on pen detection usage please refer to §4.7. A 4-wire touchscreen will be powered between X+ and Y- through a resistor RPNDT so no current will flow as long as no pressure is applied to the surface (see figure below). When a touch occurs, a current path is created bringing X+ to the level defined by the resistive divider determined by RPNDT and the sum of R1, RT and R4. th Rev 1 – 25 July 2011 15 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 13 – 4-wire Touchscreen Pen Detection When using a 5-wire touchscreen, the pen detection pull-up resistor RPNDT and digital comparator continue to monitor the X+/BR pin as in 4-wire mode. The top panel is grounded via the WIPER pin to provide the grounding path for a screen touch event. When a touch occurs, a current path is created and will bring BR to the level defined by the resistive divider determined by RPNDT and the sum of R1, RT and RW. Figure 14 – 5-wire Touchscreen Pen Detection RPNDT can be configured to 4 different values to accommodate different screen resistive values. RPNDT should be set to a value greater than 7x(Rxtot + Rytot), it is recommended to set it to max value. Pen detection uses a bias time of POWDLY/8 (digital comparator => less precision required vs analog conversion). Increasing POWDLY can improve the detection on panels with high resistance. A pen touch will set the PENSTAT bit of the RegStat register which will generate an interrupt if enabled in RegIrqMsk. A pen release will reset PENSTAT bit of the RegStat register which will generate an interrupt if enabled in RegIrqMsk. 4.5 Multitouch Measurement (4-wire only) SX8677/78 support up to two simultaneous touches on any standard 4-wire touchscreen. The simplified model for dual-touch is given in figure below. th Rev 1 – 25 July 2011 16 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Rxtot = R1 + R2 + R3 Rytot = R4 + R5 + R6 Figure 15 – Dual-touch Simplified Model The two contacts create touch resistances Rt1 and Rt2 between the two layers of the touchscreen. The SX8677/78 perform on-chip specific multitouch measurements which the host retrieves and processes with a specific software enabling the detection of the gestures described in §13.3. For optimum gesture detection, RmSelX and RmSelY parameters should be set according to table below. X/Y Panel Resistance (Ω) RmSelX/Y 100-187 000 188-312 001 313-938 010 939-1875 011 1876-4375 100 4376-9375 101 9376-18780 110 >18780 111 Table 5 – RmSelX/Y Selection Table 4.6 Digital Processing The chip offers 4 types of data processing which allows the user to make trade-offs between data throughput, power consumption and noise rejection. The parameter FILT is used to select the filter order Nfilt. The noise rejection will be improved with a high order to the detriment of power consumption. Each channel can be sampled up to 7 times and then processed to get a single consolidated coordinate. cn ≈ 1 ⋅ N N −1 ∑ i= 0 sn−i Figure 16 – Digital Processing Block Diagram th Rev 1 – 25 July 2011 17 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING FILT Nfilt 0 1 Function c n = s n No average. c 1 3 1 4079 - ----------- s + s +s n = -3 ⋅ 4095 ( n n – 1 n – 2 ) 3 ADC samples are averaged. c 2 5 n 1 4079 = --- ⋅ ----------- ( s + s +s +s +s n– 1 n –2 n – 3 n – 4) 5 4095 n 5 ADC samples are averaged. s 3 7 c s s s s s s max 1 ≥ m ax2 ≥ a ≥ b ≥ c ≥ min 1 ≥ m in 2 1 4079 ----------- s s s n = --3- ⋅ 4095 ( a + b + c) 7 ADC samples are sorted and the 3 center samples are averaged. Table 6 – Digital Processing Functions The parameter SETDLY sets the settling time between the consecutive conversions of the same channel. Figure 17 – POWDLY and SETDLY (FILT=2) In most applications, SETDLY can be set to minimum (0.5us). However, in some particular applications where an accuracy of 1LSB is required SETDLY may need to be increased. 4.7 Host Operation 4.7.1 Overview The chip has three operating modes that are configured using the I2C as defined in §11 : Manual (command ‘MAN’ and TOUCHRATE = 0). Pen detect (command ‘PENDET’ and TOUCHRATE > 0). Pen trigger (command ‘PENTRG’ and TOUCHRATE > 0). At power-up the chip is set in manual mode. 4.7.2 Manual Mode (MAN) In manual mode (MAN) the touchscreen interface is stopped and conversions must be manually triggered by the host using SELECT and CONVERT command. th Rev 1 – 25 July 2011 18 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING When a command is received, the chip executes the associated tasks listed in table below and waits for the next command. It is up to the host to sequence all actions. Pen detection is performed after each CONVERT command and if pen is not detected, no touch operation is performed. Following figures assume pen down. PENSTAT is not updated in MAN mode. To enter MAN mode the host must send the MAN command and then set TOUCHRATE = 0. Command Actions CONVERT(CHAN) Select and bias CHAN Wait for the programmed settling time (POWDLY) Convert CHAN SELECT(CHAN) Select and bias CHAN Table 7 – Manual Mode Commands As illustrated in figure below the CONVERT command will bias the channel, wait for the programmed settling time (POWDLY), and run the conversion. READ CHANNEL CONVERT(Y) I2C Y Channel Bias POWDLY Y Channel Conversion CONVSTAT NIRQ (RegIrqMsk[3]=1) Figure 18 – Manual Mode – CONVERT Command (CHAN = Y; PROXSCANPERIOD = 0) When the CONVERT command is used with CHAN=SEQ, multiple channels as defined in RegChnMsk are sampled. In this case, each channel will be sequentially biased during POWDLY before a conversion is started. At the end of each channel conversion the bias is automatically removed. READ CHANNEL CONVERT(SEQ) I2C X Channel Bias Y POWDLY POWDLY Y X Channel Conversion CONVSTAT NIRQ (RegIrqMsk[3]=1) Figure 19 – Manual Mode – CONVERT Command (CHAN = SEQ = [X;Y]; PROXSCANPERIOD = 0) In case the range of POWDLY settings available is not enough to cover the required settling time, one can use the SELECT command first to bias the channel, and then send the CONVERT command hence extending bias time. SELECT command cannot be used with CHAN=SEQ. SELECT(Y) I2C Channel Bias CONVERT(Y) READ CHANNEL Y POWDLY Channel Conversion Actual bias time Y CONVSTAT NIRQ (RegIrqMsk[3]=1) th Rev 1 – 25 July 2011 19 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 20 – Manual Mode – SELECT command (CHAN = Y; PROXSCANPERIOD = 0) At the end of the conversion(s) bit CONVSTAT will be reset which will trigger NIRQ falling edge (if enabled in RegIrqMsk). Host can then read channel data which will release NIRQ. Please note that when the SELECT command is used, the channel is converted whatever the pen status (no pen detection performed). 4.7.3 Pen Detect Mode (PENDET) In pen detect mode (PENDET) the chip will only run pen detection (continuously when pen is up, regularly as defined by TOUCHRATE when pen is down) and update PENSTAT bit in RegStat to be able to generate an interrupt (NIRQ) upon pen detection and/or release. No (touch) conversion is performed in this mode. To enter PENDET mode the host must set TOUCHRATE > 0 and then send PENDET command. To quit PENDET mode and stop the touchscreen interface the host must enter MAN mode. Pen Touch Pen Release TOUCHRATE tick PENSTAT CONVSTAT NIRQ I2C Read RegIrqSrc Idle Pen Detection Figure 21 – Pen Detect Mode (RegIrqMsk[3:2] = 11 ; PROXSCANPERIOD = 0) Please note that the next pen detection is not performed as long as NIRQ is low. If the host is too slow and doesn’t read IrqSrc before next TOUCHRATE tick, no operation is performed and this TOUCHRATE tick is simply ignored until next one. 4.7.4 Pen Trigger Mode (PENTRG) In pen trigger mode (PENTRG) the chip will perform pen detection (continuously when pen is up, regularly as defined by TOUCHRATE when pen is down) and if pen is down, will be followed by a conversion as defined in RegChanMsk. The chip will update CONVSTAT bit in RegStat and will be able to generate an interrupt (NIRQ) upon conversion completion. The chip will also update PENSTAT bit in RegStat and will be able to generate an interrupt (NIRQ) upon pen detection and/or release. The PENTRG mode offers the best compromise between power consumption and coordinate throughput. To enter PENTRG mode the host must set TOUCHRATE > 0 and then send PENTRG command. To quit PENTRG mode and stop the touchscreen interface the host must enter MAN mode. th Rev 1 – 25 July 2011 20 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Pen Touch Pen Release TOUCHRATE tick PENSTAT CONVSTAT NIRQ I2C Read Channel Idle Touch Conversion Pen Detection Figure 22 – Pen Trigger Mode (RegIrqMsk[3:2] = 10 ; PROXSCANPERIOD = 0) Please note that to prevent data loss, the next pen detection and conversion are not performed as long as all current channel data (i.e. channels selected in RegChanMsk) have not been read. If the host is too slow and doesn’t read all channel data before next TOUCHRATE tick, no operation is performed and this TOUCHRATE tick is simply ignored until next one. 4.7.5 Maximum Throughput vs. TOUCHRATE setting In PENTRG mode the TOUCHRATE parameter is used to define the required coordinate’s throughput/rate. However, as previously mentioned, in order for a new conversion to be performed the current conversion must be completed and all relevant channel data must have been read by the host. If this condition is not met when the next TOUCHRATE tick occurs, the tick is ignored and the condition checked again at the next one. This will result in reduced actual rate vs what has been programmed in the TOUCHRATE parameter. This is illustrated in figures below. TOUCHRATE tick NIRQ I2C Read Channel Tconv Tcom Tconv+Tcom < Trate Trate Idle Pen Detection = => Actual rate = TOUCHRATE Touch Conversion Figure 23 – Correct TOUCHRATE setting th Rev 1 – 25 July 2011 21 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Not ready, tick ignored TOUCHRATE tick NIRQ Trate < Tconv+Tcom < n.Trate I2C Read Channel Tconv Tcom Trate Idle Pen Detection => Actual rate = TOUCHRATE/n = Touch Conversion Figure 24 – Incorrect (too high) TOUCHRATE setting In order to prevent this, one can estimate the maximum throughput achievable and set TOUCHRATE parameter accordingly. MaxThroughput = 1 / (Tconv+Tcom) Tcom is the time between the end of conversion (ie NIRQ falling edge) and the end of channel data reading (i.e. NIRQ rising edge). Maximum throughput implies that the host reacts “instantaneously” to NIRQ falling edge: Tc om = (8 + 16 × Ncha n ) × T I 2C Tconv is the total conversion time: Tconv ( us ) = 47 ⋅ Tos c + Nc han ⋅ ( P OWD LY + ( Nf ilt – 1 ) ⋅ SETD LY + ( 21Nfilt + 1 ) ⋅ Tos c ) - TI2C is the period of the I2C clock SCL - Nfilt = {1,3,5,7} based on the order defined for the filter FILT - Nchan = {1,2,3,4,5} based on the number of channels defined in RegChanMsk - POWDLY = 0.5us to 18.19ms, settling time as defined in RegTS0 - SETDLY = 0.5us to 18.19ms, settling time when filtering as defined in RegTS2 - Tosc is the period of the internal oscillator FOSCH Some examples of maximum throughputs achievable with an I2C running at 400kHz are given below. Nchan Nfilt POWDLY [us] SETDLY [us] Tconv [us] Tcom [us] Total [us] CR [kcps] ECR [kcps] SR [ksps] ESR [ksps] 2 1 0.5 0.5 51.7 100 151.7 6.6 13.2 6.6 13.2 2 3 35.5 0.5 170.6 100 270.6 3.7 7.4 11.1 22.2 2 5 2.2 0.5 152.8 100 252.8 4 8 20 40 4 3 35.5 0.5 315.0 200 515 1.9 7.6 5.7 22.8 Table 8 – Maximum Throughputs Examples - CR = Coordinate Rate - ECR = Equivalent Coordinate Rate = CR x Nchan - SR = Sampling Rate = CR x Nfilt - ESR = Equivalent Sampling Rate = SR x Nchan = CR x Nfilt x Nchan For proper operation, the TOUCHRATE parameter should not exceed the theoretical maximum throughput CR. th Rev 1 – 25 July 2011 22 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5 PROXIMITY SENSING INTERFACE (SX8677) 5.1 Introduction The purpose of the proximity sensing interface is to detect when a conductive object (usually a body part i.e. finger, palm, face, etc) is in the proximity of the system. This is commonly used in power-sensitive mobile applications to turn the screen’s LCD ON/OFF depending on user’s finger/palm/face proximity. The chip’s proximity sensing interface is based on capacitive sensing technology and shares the ADC with the touchscreen interface (Cf §5.4.2). An overview is given in figure below. Finger, palm, face, etc Sensor Shield Analog Front-End (AFE) PROXSTAT Digital 0 1 0 Processing SX8677 Figure 25 – Proximity Sensing Interface Overview The sensor can be the top layer of the touchscreen or a simple copper area on the PCB (programmable in PROXSENSORCON). Its capacitance (to ground) will vary when a conductive object is moving in its proximity. The optional shield can be the bottom layer of the touchscreen or a simple copper area on the PCB (programmable in PROXSHIELDCON) below/under/around the sensor. It is used to protect the sensor against potential surrounding noise sources and improve its global performance. It also brings directivity to the sensing, for example sensing objects approaching from top only. The analog front-end (AFE) performs the raw sensor’s capacitance measurement and converts it into a 12 bit digital code. It also controls the shield. See §5.2 for more details. The digital processing block computes the raw capacitance measurement from the AFE and extracts a binary information PROXSTAT corresponding to the proximity status, i.e. object is “Far” or “Close”. It also triggers AFE operations (compensation, etc). See §5.3 for more details. To save power since the proximity event is slow by nature, the block will be waken-up regularly at every programmed scan period (PROXSCANPERIOD) to sense and then process a new proximity sample. The block will be in idle mode most of the time. This is illustrated in figure below Figure 26 – Proximity Sensing Sequencing th Rev 1 – 25 July 2011 23 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.2 Analog Front-End (AFE) 5.2.1 Capacitive Sensing Basics Capacitive sensing is the art of measuring a small variation of capacitance in a noisy environment. As mentioned above, the chip’s proximity sensing interface is based on capacitive sensing technology. In order to illustrate some of the user choices and compromises required when using this technology it is useful to understand its basic principles. To illustrate the principle of capacitive sensing we will use the simplest implementation where the sensor is a copper plate on a PCB but the exact same principles apply if the sensor is the touchscreen’s top plate. The figure below shows a cross-section and top view of a typical capacitive sensing implementation. The sensor connected to the chip is a simple copper area on top layer of the PCB. It is usually surrounded (shielded) by ground for noise immunity (shield function) but also indirectly couples via the grounds areas of the rest of the system (PCB ground traces/planes, housing, etc). For obvious reasons (design, isolation, robustness …) the sensor is stacked behind an overlay which is usually integrated in the housing of the complete system. When the touchscreen is used for sensing the overlay corresponds to the thin and flexible protection film covering the top panel. PCB copper Overlay PCB dielectric Sensor Cut view Top view Ground Figure 27 – Typical Capacitive Sensing Implementation When the conductive object to be detected (finger/palm/face, etc) is not present, the sensor only sees an inherent capacitance value CEnv created by its electrical field’s interaction with the environment, in particular with ground areas. When the conductive object (finger/palm/face, etc) approaches, the electrical field around the sensor will be modified and the total capacitance seen by the sensor increased by the user capacitance CUser. This phenomenon is illustrated in the figure below. Figure 28 – Proximity Effect on Electrical Field and Sensor Capacitance th Rev 1 – 25 July 2011 24 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING The challenge of capacitive sensing is to detect this relatively small variation of CSensor (CUser usually contributes for a few percents only) and differentiate it from environmental noise (CEnv also slowly varies together with the environment characteristics like temperature, etc). For this purpose, the chip integrates an auto offset compensation mechanism which dynamically monitors and removes the CEnv component to extract and process CUser only. See §5.2.5 for more details. In first order, CUser can be estimated by the formula below: CUser = ε 0 ⋅ εr ⋅ A d A is the common area between the two electrodes hence the common area between the user’s finger/palm/face and the sensor. d is the distance between the two electrodes hence the proximity distance between the user and the system. ε 0 is the free space permittivity and is equal to 8.85 10e-12 F/m (constant) ε r is the dielectric relative permittivity. When performing proximity sensing the dielectric relative permittivity is roughly equal to that of the air as the overlay is relatively thin compared to the detection distance targeted. Typical permittivity of some common materials is given in the table below. Material Glass FR4 Acrylic Glass Wood Air Typical 8 5 3 2 1 εr From the discussions above we can conclude that the most robust and efficient design will be the one that minimizes CEnv value and variations while improving CUser. 5.2.2 AFE Block Diagram Figure 29 – Analog Front-End Block Diagram th Rev 1 – 25 July 2011 25 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.2.3 Capacitance-to-Voltage Conversion (C-to-V) PROXSENSORCON defines which pin will act as the sensor during proximity sensing operations. In the typical case, the touchscreen top layer is used as the sensor (exact pin/electrode depends on screen type/structure). Else, the sensor can also be “external”, i.e. connected to AUX2. The sensitivity of the interface is defined by PROXSENSITIVITY; for obvious power consumption reasons it is recommended to set it as low as possible. As a last resort and only if the sensor is “external”, PROXBOOST can be set to allow higher sensitivity if needed. PROXFREQ defines the operating frequency of the interface and should be set as high as possible for power consumption reasons. If needed, PROXHIGHIM enables a high noise immunity mode at the expense of increased power consumption. 5.2.4 Shield Control PROXSHIELDCON defines which pin will act as the shield during proximity sensing operations. In the typical case, the shield will usually be the touchscreen bottom layer (exact pin/electrode depends on screen type/structure). Else, the shield can also be “external”, ie a simple copper area on the PCB connected to AUX3. 5.2.5 Offset Compensation Offset compensation consists in performing a one time measurement of CEnv and subtracting it to the total capacitance CSensor in order to feed the ADC with the closest contribution of CUser only. Figure 30 – Offset Compensation Block Diagram The ADC input CUser is the total capacitance CSensor to which CEnv is subtracted. There are five possible compensation sources which are illustrated in the figure below. When set to 1 by any of these sources, PROXCOMPSTAT will only be reset once the compensation is completed. Figure 31 – Compensation Request Sources th Rev 1 – 25 July 2011 26 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Block startup: a compensation is automatically requested when the proximity sensing is enabled via PROXSCANPERIOD. I2C: a compensation can be manually requested anytime by the host through I2C interface. PROXAVG update: a compensation can be automatically requested if it is detected that CEnv has drifted beyond a set level since the last compensation. PROXCOMPPRD: a compensation can be automatically requested at a predefined rate programmed by the host. PROXSTUCK: a compensation can be automatically requested if it is detected that the proximity “Close” state is lasting abnormally long. Please note that the compensation request flag can be set anytime but the compensation itself is always done at the beginning of a scan period to keep all parameters coherent (PROXRAW, PROXAVG, PROXDIFF), see §5.3.2. 5.2.6 Analog-to-Digital Conversion (ADC) A 12-bit ADC is used to convert the capacitance information into a digital 12-bit word PROXRAW. The ADC is shared with the touchscreen interface using time multiplexing (see §5.4.2 for more details). 5.3 Digital Processing 5.3.1 Overview The main purpose of the digital processing block is to convert the raw capacitance information coming from the AFE (PROXRAW) into a robust and reliable digital flag (PROXSTAT) indicating if the user’s finger/hand/head is close to the proximity sensor. The offset compensation performed in the AFE is a one time measurement. However, the environment capacitance CEnv may vary with time (temperature, nearby objects, etc). Hence, in order to get the best estimation of CUser (PROXDIFF) it is needed to dynamically track and subtract CEnv variations. This is performed by filtering PROXUSEFUL to extract its slow variations (PROXAVG). PROXDIFF is then compared to user programmable threshold to extract PROXSTAT flag. Figure 32 – Digital Processing Block Diagram Digital processing sequencing is illustrated in figure below. At every scan period wake-up (defined by PROXSCANPERIOD), the block updates sequentially PROXRAW, PROXUSEFUL, PROXAVG, PROXDIFF and PROXSTAT before going back to Idle mode. th Rev 1 – 25 July 2011 27 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 33 – Digital Processing Sequencing Digital processing block also updates CONVSTAT (set during proximity operations) and PROXCOMPSTAT (set when compensation is currently pending execution or competition) 5.3.2 PROXRAW Update PROXRAW update consists mainly in starting the AFE and waiting for the new PROXRAW value to be ready. If a compensation was pending it is performed first. th Rev 1 – 25 July 2011 28 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 34 – ProxRaw Update 5.3.3 PROXUSEFUL Update PROXUSEFUL update consists in filtering PROXRAW upfront to remove its potential high frequencies components(system noise, interferer, etc) and extract only user activity (few Hz max) and slow environment changes. Figure 35 – PROXUSEFUL Update F(PROXRAW ; PROXUSEFUL[n-1] ; PROXRAWFILT) = (1 - PROXRAWFILT).PROXRAW + PROXRAWFILT.PROXUSEFUL[n-1] th Rev 1 – 25 July 2011 29 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.3.4 PROXAVG Update PROXAVG update consists in averaging PROXUSEFUL to ignore its “fast” variations (i.e. user finger/palm/hand) and extract only the very slow variations of environment capacitance CEnv. One can program positive and negative debounced thresholds (PROXAVGPOSTHRESH/PROXAVGPOSDEB and PROXAVGNEGTHRESH/PROXAVGNEGDEB) within which PROXAVG can vary without triggering compensation (ie small acceptable environment drift). Large positive values of PROXUSEFUL are considered as normal (user finger/hand/head) but large negative values are considered abnormal and should be compensated quickly. For this purpose, the averaging filter coefficient can be set independently for positive and negative variations via PROXAVGPOSFILT and PROXAVGNEGFILT. Typically we have PROXAVGPOSFILT > PROXAVGNEGFILT to filter out (abnormal) negative events faster. To prevent PROXAVG to be “corrupted” by user activity (should only reflect environmental changes) it is freezes when proximity is detected. Figure 36 – ProxAvg vs Proximity Event th Rev 1 – 25 July 2011 30 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 37 – ProxAvg Update F(PROXUSEFUL ; PROXAVG[n-1] ; PROXAVGxxxFILT) = (1 - PROXAVGxxxFILT).PROXUSEFUL + PROXAVGxxxFILT.PROXAVG[n-1] xxx = POS or NEG th Rev 1 – 25 July 2011 31 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.3.5 PROXDIFF Update PROXDIFF update consists in the complementary operation i.e. subtracting PROXAVG to PROXUSEFUL to ignore slow capacitances variations (CEnv) and extract only the user related variations i.e. CUser. Figure 38 – ProxDiff Update 5.3.6 PROXSTAT Update PROXSTAT update consists in taking PROXDIFF information (CUser), comparing it with a user programmable threshold PROXTHRESH and finally updating PROXSTAT accordingly. When PROXSTAT=1, PROXAVG is frozen to prevent the user proximity signal averaging and hence absorbed into CEnv. Figure 39 – PROXSTAT Update th Rev 1 – 25 July 2011 32 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5.4 Host Operation 5.4.1 General Description If PROXIRQSEL = 0, an interrupt can be triggered when the user is detected to be close, detected to be far, or both (PROXCLOSEIRQEN, PROXFARIRQEN). User in range User out of range PROXSCANPERIOD tick PROXSTAT CONVSTAT NIRQ I2C Read RegIrqSrc Pen Detection Proximity Sensing (Analog + Digital) Figure 40 – Proximity Sensing Host Operation (Pen Trigger Mode ; RegIrqMsk[6:4] = 110 ; PROXIRQSEL = 0) If PROXIRQSEL = 1, instead of the proximity “Far” state, an interrupt can be triggered at the end of each proximity sensing operation indicating to the host when the proximity sensing block is running (PROXCONVDONEIRQEN). This may be used by the host to synchronize noisy system operations or to read PROXRAW, PROXUSEFUL, PROXAVG, PROXDIFF synchronously for monitoring purposes. User in range User out of range PROXSCANPERIOD tick PROXSTAT CONVSTAT NIRQ I2C Read RegIrqSrc Pen Detection Proximity Sensing (Analog + Digital) Figure 41 – Proximity Sensing Host Operation (Pen Trigger Mode ; RegIrqMsk[6:4] = 010 ; PROXIRQSEL = 1) In both cases above, an interrupt can also be triggered at the end of compensation (PROXCOMPDONEEN). 5.4.2 Proximity Sensing vs Touch Operations As previously mentioned, touch and proximity operations share the same ADC and hence the chip implements time multiplexing between these two types of operations. Also, proximity sensing doesn’t need to be performed while pen is down (not needed as host knows already something touches the screen). In all operating modes, if PROXSCANPERIOD = 0, no proximity operation is performed (i.e. §4.7). The following hence assumes PROXSCANPERIOD != 0. For simplicity we also assume that NIRQ is only used for reporting touch operations i.e. RegIrqMsk[6:4] = 000 (PROXSTAT mapped to AUX pin, or polled via I2C). In MAN mode, a CONVERT command (if not preceded by a SELECT command) will perform a proximity sensing operation before the touchscreen operation, whatever the pen status. Hence please note that if the th Rev 1 – 25 July 2011 33 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING touchscreen is used as the proximity sensor and is being touched when the conversion is performed, the proximity measurement result may be incorrect. READ CHANNEL CONVERT Y I2C Y Channel Bias POWDLY PROX Channel Conversion Y CONVSTAT NIRQ (RegIrqMsk[6:3]=0001) Figure 42 – Manual Mode – CONVERT Command (CHAN = Y ; PROXSCANPERIOD != 0; Pen down) If the screen is not touched, only the proximity sensing operation is performed. READ CHANNEL CONVERT Y I2C Channel Bias PROX Channel Conversion CONVSTAT NIRQ (RegIrqMsk[6:3]=0001) Figure 43 – Manual Mode – CONVERT Command (CHAN = Y ; PROXSCANPERIOD != 0, Pen up) In PENDET and PENTRG mode, a proximity sensing operation will be performed regularly as defined in PROXSCANPERIOD, but only if pen is not detected. Pen Touch Pen Release TOUCHRATE tick PENSTAT CONVSTAT NIRQ I2C Read RegIrqSrc Idle Touch Conversion Pen Detection Proximity Sensing Figure 44 – Pen Detect Mode (RegIrqMsk[6:2] = 00011 ; PROXSCANPERIOD = 001 ie 1/TOUCHRATE) th Rev 1 – 25 July 2011 34 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Pen Touch Pen Release TOUCHRATE tick PENSTAT CONVSTAT NIRQ I2C Read Channel Idle Touch Conversion Pen Detection Proximity Sensing Figure 45 – Pen Trigger Mode (RegIrqMsk[6:2] = 00010 ; PROXSCANPERIOD = 001 ie 1/TOUCHRATE) 5.4.3 Minimum Scan Period (i.e. PROXSCANPERIOD) Similarly to touch operations (Cf. §4.7.5), if PROXSCANPERIOD is too short for proximity sensing operations to be completed, the rate tick(s) affected are ignored until operations are completed and the following tick is taken into account for the next planned operation. Please note that compensation lasts about ~16 times longer than a normal proximity sensing operation. th Rev 1 – 25 July 2011 35 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 6 HAPTICS INTERFACE (SX8677/78) 6.1 Introduction Haptics technology is commonly used in systems which include a touchscreen interface. Its purpose is to provide tactile feedback to the user to acknowledge a touch event hence improving greatly the robustness of the system and user comfort and perception. The on-chip haptics interface is designed to drive two common actuator types: Eccentric Rotating Mass (ERM) and Linear Resonant Actuator (LRA). This is performed without any external component due to fully embedded analog processing and with very limited host interaction due to the embedded digital processing block. Figure 46 – Haptics Interface Overview The host configures drive parameters from the I2C port according to the particular haptics load to be used. The haptics drive level is then controlled in real time by either of two methods: by a dedicated digital pin, MIN, which accepts a pulse-width-modulated (PWM) digital signal; or by writing the desired output level directly to a register via the I2C interface. This digital information is filtered to prevent fast transitions and hence high current spikes (HAPTBW), converted into the analog domain by an 8-bit DAC, and finally amplified (HAPTGAIN) to provide a differential signal between MOUTP and MOUTN pins which can be directly connected to the motor thanks to their high drive current capability. For better isolation from the rest of the chip, the haptics interface analog block has its own power supply pins MVDD and MGND. The haptics interface is enabled when HAPTTYPEEN != 0. 6.2 ERM Load 6.2.1 Introduction An ERM is a DC motor with an off-balance load to create a vibration. Speed and direction are controlled by the applied voltage. The ERM load is selected when HAPTTYPEEN = 10. th Rev 1 – 25 July 2011 36 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Ac l ce in at er g Figure 47 – ERM Drive Signal Example If AmplitudeCode is within HAPTSQUELCH range (for more than 512/MIN_Freq in PWM mode, for more than 512/FOSCL in I2C mode): VMOUT = 0V Else: VMOUT(V) = (AmplitudeCode / 127) x 1.135 * HAPTGAIN AmplitudeCode (signed) is defined differently depending on the mode selected (PWM or I2C), see below. Please note that whatever setting, VMOUT is physically limited to [MVDD;-MVDD], i.e. saturation effect. 6.2.2 PWM Mode PWM mode is selected when HAPTMODE = 0. In this mode, AmplitudeCode is extracted/updated at each MIN period from MIN_DutyCycle: • • • • • • • MIN_DutyCycle ≈ 0% => AmplitudeCode = -127 … MIN_DutyCycle = 49.6% => AmplitudeCode = -1 MIN_DutyCycle = 50% => AmplitudeCode = 0 MIN_DutyCycle = 50.4% => AmplitudeCode = +1 … MIN_DutyCycle ≈ 100% => AmplitudeCode = +127 6.2.3 I2C Mode I2C mode is selected when HAPTMODE = 1. In this mode, AmplitudeCode = HAPTAMP (signed, internally sampled at FOSCL). MIN is not used and should be grounded. HAPTRANGE must be set to 1. 6.3 LRA Load 6.3.1 Introduction An LRA is a spring and mass with an electro-magnetic coil to move the mass. It is operated by applying an AC signal at its resonant frequency (typ. ~175 Hz). Like pushing a swing at its resonance, it doesn’t need much energy to keep it going, so drive current requirements are much lower than for ERMs. LRAs have moderately high Q factors so that the drive frequency must match the resonant frequency within a few Hz to get optimum amplitude. LRA load is selected when HAPTTYPEEN = 01. th Rev 1 – 25 July 2011 37 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Figure 48 – LRA Drive Signal Example The carrier frequency of VMOUT_Freq is defined as following: VMOUT_Freq(Hz) = (MIN_Freq / HAPTRANGE) (PWM mode) OR VMOUT_Freq(Hz) = (MIN_Freq / HAPTRANGE) / (HAPTTIMER +1) (I2C mode) If AmplitudeCode is within HAPTSQUELCH range (for more than 512/VMOUT_Freq): VMOUT_Envelope = 0V Else: VMOUT_Envelope(V) = (AmplitudeCode / 127) x 1.135 * HAPTGAIN AmplitudeCode (signed) is defined differently depending on the mode selected (PWM or I2C), see below. Please note that whatever setting, VMOUT is physically limited to [MVDD;-MVDD], ie saturation effect. 6.3.2 PWM Mode PWM mode is selected when HAPTMODE = 0. In this mode, AmplitudeCode is extracted/updated at each MIN period from MIN_DutyCycle: • • • • • • • MIN_DutyCycle ≈ 0% => AmplitudeCode = -127 … MIN_DutyCycle = 49.6% => AmplitudeCode = -1 MIN_DutyCycle = 50% => AmplitudeCode = 0 MIN_DutyCycle = 50.4% => AmplitudeCode = +1 … MIN_DutyCycle ≈ 100% => AmplitudeCode = +127 6.3.3 I2C Mode I2C mode is selected when HAPTMODE = 1. In this mode, AmplitudeCode = HAPTAMP (signed, internally sampled at MIN_Freq). MIN is still used to extract VMOUT carrier frequency. 6.4 Short-Circuit Protection The haptics interface integrates a short-circuit protection circuit which detects when MIDD is abnormally high i.e. above ISHORT. Under a short-circuit event (HAPTSHORTSTAT=1) the haptics block will stop operation (MOUTN & MOUTP grounded). When the short-circuit is removed the haptics operations will resume normally. th Rev 1 – 25 July 2011 38 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 7 TEMPERATURE SENSOR The chip includes a temperature sensor which monitors the chip’s junction temperature. Its purpose is to provide over-temperature information to the host and if needed automatically shutdown chip operation for thermal protection. Figure 49 – Temperature Sensor Overview If TEMPALWAYSON = 0 (default), the temperature sensor will perform measurements only if the chip is active i.e. touchscreen interface running (Op. Mode != MAN), proximity sensing interface enabled (PROXSCANPERIOD != 0) or haptics interface enabled (HAPTTYPEEN != 00). The temperature sensor will perform a measurement every ~32 ms (1024/FOSCL) but not during ADC conversions (temperature sensing delayed accordingly). If TEMPALWAYSON = 1, the temperature sensor will always perform a measurement every ~32 ms independently from chip activity (i.e. also when the chip is inactive and during ADC conversions). Each measurement is compared with two internally hard-coded thresholds: Warning level: typ. 120°C (TWRNG). Alarm level: typ. 155°C (TALRM) Each of these thresholds is associated to a status flag (TEMPWARNINGSTAT, TEMPALARMSTAT) which edges can be mapped to generate an interrupt to the host. Additionally, during an alarm situation (i.e. temperature > alarm level) all chip operations (i.e. touchscreen, proximity, haptics) are automatically shutdown until the temperature goes below the alarm level. After a shutdown event all stored conversion data are thrown away. Cycling operations (TOUCHRATE > 0) will rd resume from the start (i.e. if a 4 channel conversion is stopped during the 3 channel conversion, when resuming, the 4 channels will be converted again). If the user was running some manual operation (SELECT, CONVERT), the corresponding command will have to be re-issued. The haptics operations will resume directly. th Rev 1 – 25 July 2011 39 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 8 INTERRUPT (NIRQ) 8.1 Introduction The purpose of the NIRQ pin is to indicate to the host (via a falling edge) when any of the events considered being time-critical has occurred. Non time-critical events can be monitored via I2C by reading regularly the relevant status bits. 8.2 Registers Overview 8.2.1 RegIrqMsk This register allows the host to decide which interrupt sources he wants to monitor via the NIRQ signal. Please note that a reset event will always trigger NIRQ falling edge whatever RegIrqMsk (Cf §10) 8.2.2 RegIrqSrc This register indicates to the host which of the interrupt sources triggered the NIRQ signal. More than one bit can be set if several events occurred before host reads the register. If bit 3 is OFF, reading the register will clear it together with releasing NIRQ signal. Else, if bit 3 is ON and we are in MAN or PENTRG mode, both register and NIRQ will be cleared only once all channel data have been read. All ADC related operations (touch conversion, proximity conversion, pen detection) are stopped as long as all channel data have not been read. Bits which RegIrqMsk corresponding bits are set to 0 (ie source not monitored) will always read 0 even if the event actually occurred. 8.2.3 RegStat This register regroups all status information of the chip and is used by all interrupt sources to detect the relevant events. For each bit, if the relevant block is ON its value is constantly updated, else it is set to 0. This register update is completely independent from RegIrqMsk. 8.3 - Host Procedure Configure the different blocks parameters(TS, Proximity, etc) Program RegIrqMsk to start monitoring what is considered to be “time-critical” events Enable the blocks to start RegStat update and hence NIRQ process. Each time NIRQ falling edge occurs, read RegIrqSrc to know which “time-critical” event occurred (+ read channel data if relevant) In addition, RegStat can be read anytime to get the whole picture including also what is considered to be “non time-critical” information. th Rev 1 – 25 July 2011 40 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 9 AUXILIARY PINS (AUX1/AUX2/AUX3) The chip has three auxiliary pins which can be used: 1. By the touchscreen interface when using a 5-wire touchscreen (WIPER=AUX1) 2. By the proximity sensing interface (PROXSENSORCON and PROXSHIELDCON) to use an external sensor and/or shield instead of the touchscreen’s plates 3. By the host (RegAux0-1) to monitor any RegStat and/or RegIrqSrc bits in real time without having to use NIRQ or perform I2C polling. th Rev 1 – 25 July 2011 41 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 10 RESET 10.1 Hardware (POR and NRST) The chip generates its own power on reset (POR) signal after a power supply is connected to the VDD pin. NRST input pin can be used to reset the chip anytime, it must be connected to VDD (or greater) either directly (if not used), or via a resistor. 1 2 3 VDD VPOR Reset Signal Undefined tRESET NIRQ tPULSE Undefined Figure 50 – Hardware Reset Conditions 1. Device behavior is undefined until VDD rises above VPOR, at which point internal reset procedure is started and NIRQ is kept low. 2. After tRESET, the reset procedure is completed and NIRQ is released high. 3. In operation, the chip may be reset at anytime by an external device driving NRST low for tPULSE or longer. NIRQ will go low during the reset phase and chip can be accessed normally again after NIRQ rising edge. Additionally bit RESETSTAT will be set (cleared when reading RegStat) 10.2 Software (RegReset) Writing 0xDE to RegReset register will reset the chip and all registers to their default values. NIRQ will go low during the reset phase and chip can be accessed normally again after NIRQ rising edge. Additionally bit RESETSTAT will be set (cleared when reading RegStat). 10.3 ESD Event (RESETSTAT) In case of ESD event, the chip can reset to protect its internal circuitry. NIRQ will go low during the reset phase and chip can be accessed normally again after NIRQ rising edge. Additionally bit RESETSTAT will be set (cleared when reading RegStat). th Rev 1 – 25 July 2011 42 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 11 I2C INTERFACE 11.1 Introduction The chip is a read-write slave-mode I2C device and complies with the Philips I2C standard Version 2.1 dated January, 2000. The chip has a few user-accessible internal 8-bits registers to set the various parameters of operation (Cf. §12 for detailed configuration registers description). The I2C interface has been designed for program flexibility, in that once the slave address has been sent to the chip enabling it to be a slave transmitter/receiver, any register can be written or read independently of each other. The start and stop commands frame the data-packet and the repeat start condition is allowed if necessary. 2 lines are used to exchange data between an external master host and the slave device: • SCL : Serial CLock • SDA : Serial DAta Seven bit addressing is used and ten bit addressing is not allowed. Any general call address will be ignored by the chip. The chip is not CBUS compatible and can operate in standard mode (100kbit/s) or fast mode (400kbit/s). 11.2 I2C Address On the QFN package an ADDR pin is made available to select between the two pre-programmed I2C addresses of the device. On the CSP package ADDR is internally connected to ground. This is illustrated in table below. Package QFN CSP ADDR 0 1 0 Address Description First I2C address 0x48 (1001000) Second I2C address 0x49 (1001001) 0x48 (1001000) First (and unique) I2C address Table 9 – I2C Address Please note that upon request, a custom I2C Address can be pre-programmed by Semtech. 11.3 Write Register The I2C write register sequence is given in figure below. After the start condition [S], the chip slave address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a write. The chip then acknowledges [A] that it is being addressed, and the host sends a CR byte consisting in ‘00’ followed by the chip register address (RA). The chip acknowledges [A] and the host sends the appropriate data byte (WD0) to be written. Again the chip acknowledges [A]. In case the host needs to write more data, a succeeding data byte will follow (WD1), acknowledged by the slave [A]. This sequence will be repeated until the host terminates the transfer with the stop condition [P]. Figure 51 – I2C Write Register The register address increments automatically when successive data bytes (WD1...WDn) are supplied by the host. th Rev 1 – 25 July 2011 43 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING The correct sampling of the screen by the chip and the host I2C bus traffic are events that might occur simultaneously. The chip will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after the last received command bit (see figure above). 11.4 Read Register The I2C read register sequence is given in figure below. After the start condition [S], the chip slave address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a write. The chip then acknowledges [A] that it is being addressed, and the host responds with a CR byte consisting in ‘01’ followed by the register address (RA). The chip acknowledges [A] and the host sends the repeated start Condition [Sr]. Once again, the chip slave address (SA) is sent, followed by an eighth bit (R=‘1’) indicating a read. The chip responds with an acknowledge [A] and the data byte (RD0). If the host needs to read more data it will acknowledge [A] and the chip will send the next data byte (RD1). This sequence will be repeated until the host terminates the transfer with a NACK [N] followed by a stop condition [P]. Figure 52 – I2C Read Register The register address increments automatically when successive data bytes (RD1...RDn) are read by the host. The correct sampling of the screen by the chip and the host I2C bus traffic are events that might occur simultaneously. The chip will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after the last received command bit (see figure above). 11.5 Write Command (Touchscreen Interface) The I2C write command sequence is given in figure below. After the start condition [S], the chip slave address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a write. The chip then acknowledges [A] that it is being addressed, and the host responds with a CR byte consisting in Command(7:0) (see table below). The chip acknowledges [A] and the host sends a stop [P]. Figure 53 – I2C Write Command The sampling of the screen by the chip and the host I2C bus traffic are events that might occur simultaneously. The chip will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after the last received command bit (see figure above). th Rev 1 – 25 July 2011 44 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Command SELECT CONVERT MAN PENDET PENTRG Command(7:0) 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 Channel X Y Z1 Z2 RX RY SEQ X X X X X Function Chan(2:0) Select and bias channel. Chan(2:0) Convert channel. X X X Enter manual mode. X X X Enter pen detect mode. X X X Enter pen trigger mode. Table 10 : Command Codes Chan(2:0) Description 0 0 0 X channel 0 0 1 Y channel 0 1 0 First channel for pressure measurement 0 1 1 Second channel for pressure measurement 1 0 1 X multitouch measurement 1 1 0 Y multitouch measurement 1 1 1 Channels enabled in RegChanMsk register Table 11 : Channel Codes 11.6 Read Channel (Touchscreen Interface) The I2C read channel sequence is given in figure below. After the start condition [S], the chip slave address (SA) is sent, followed by an eighth bit (R=‘1’) indicating a read. The chip responds with an acknowledge [A] and the first data byte (RD0). The host sends an acknowledge [A] and the chip responds with the second data byte (RD1). If the host needs to read more channels, it will acknowledge [A] and the chip will send the next data bytes. This sequence will be repeated until the host terminates with a NACK [N] followed immediately by a stop [P]. The channel data that can be read is defined by RegChanMsk, or the last convert command in manual mode. A maximum number of 12 data bytes can be read when all channels (X, Y, Z1, Z2, RX, RY) are activated in RegChanMsk. The STOP [P] (if following the last valid data) releases high the NIRQ line. All ADC related operations (touch conversion, proximity conversion, pen detection) are stopped as long as all valid channel data have not been read (ie as long as NIRQ is low). Figure 54 – I2C Read Channel The sampling of the screen by the chip and the host I2C bus traffic are events that might occur simultaneously. The chip will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after the address and read bit have been sent for the I2C read channels command (see figure above). The channel data is sent with the following order: X, Y, Z1, Z2, RX, RY. It is coded as described in figure below Typical applications require only X and Y coordinates, thus only 4 bytes of data will be read in this case. th Rev 1 – 25 July 2011 45 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 0 CHAN(2:0) D(7:0) D(11:8) RD1 RD0 Figure 55 – Channel Data Format The 3 bits CHAN(2:0) are defined in the previous table and show which channel data is referenced. The channel data D(11:0) is of unsigned format and corresponds to a value between 0 and 4095. The chip will return 0xFFFF in case of invalid data; this occurs when: • • host tries to read channels which have not been converted. For example if the chip converts X and Y and the host tries to read X, Y, Z1 and Z2. a conversion has been done while the screen wasn’t touched , i.e. pen up (not detected). th Rev 1 – 25 July 2011 46 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 12 REGISTERS DETAILED DESCRIPTION Address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x3F Name RegTouch0 RegTouch1 RegTouch2 RegTouch3 RegChanMsk RegHapt0 RegHapt1 RegHapt2 RegHapt3 RegHapt4 RegHapt5 RegProx0 RegProx1 RegProx2 RegProx3 RegProx4 RegProx5 RegProx6 RegProx7 RegProx8 RegProx9 RegProx10 RegProx11 RegProx12 RegProx13 RegProx14 RegProx15 RegProx16 RegProx17 RegProx18 RegProx19 RegProx20 RegProx21 RegProx22 RegIrqMsk RegIrqSrc RegStat RegAux0 RegAux1 RegReset Default 0x00 0x20 0x00 0x00 0xC0 0x00 0x00 0x00 0x80 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x01 0x00 0x08 0x00 0x00 0x00 0x00 0x00 Description Touchscreen Interface Haptics Interface and Temperature Sensor Proximity Sensing Interface Interrupt and Chip Status Auxiliary Functions Software Reset Table 12 : Registers Overview NOTES: 1) Addresses not listed above are reserved and should not be written. 2) Reserved bits should be left to their default value unless otherwise specified. 3) Proximity related registers/bits do not apply to SX8678. th Rev 1 – 25 July 2011 47 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:4 Variable TOUCHRATE Default 0000 Description Defines the touch coordinates acquisition rate: 0000 : OFF. 0001 : 10 cps 0010 : 20 cps 0011 : 40 cps 0100 : 60 cps 0101 : 80 cps 0110 : 100 cps 0111 : 200 cps 1000 : 300 cps 1001 : 400 cps 1010 : 500 cps 1011 : 1 kcps 1100 : 2 kcps 1101 : 3 kcps 1110 : 4 kcps 1111 : 5 kcps 3:0 POWDLY 0000 Values above assume typical FOSCL, else vary accordingly. Defines the bias settling time for each channel’s first conversion: 0000 : 0.5 us 0001 : 1.1 us 0010 : 2.2 us 0011 : 4.4 us 0100 : 8.9 us 0101 : 17.8 us 0110 : 35.5 us 0111 : 71.0 us 1000 : 142 us 1001 : 284 us 1010 : 768 us 1011 : 1.14 ms 1100 : 2.27 ms 1101 : 4.75 ms 1110 : 9.09 ms 1111 : 18.19 ms Values above assume typical FOSCH, else vary accordingly. Table 13 : RegTouch0 (Addr 0x00) Bits 7:5 4 3:2 1:0 Variable Reserved TSTYPE RPNDT FILT Default 001 0 Description Defines the type of touchscreen: 00 0 : 4-wire 1 : 5-wire Defines the pen detection circuit’s pull-up resistor value: 00 00 : 114 kOhms 01 : 228 kOhms 10 : 57 kOhms 11 : 28 kOhms Defines the channel filtering algorithm: 00 : OFF (Nfilt = 1) 01 : 3 sample averaging (Nfilt = 3) 10 : 5 sample averaging (Nfilt = 5) 11 : 3 sample averaging after removal of extreme values (Nfilt = 7) Table 14 : RegTouch1 (Addr 0x01) th Rev 1 – 25 July 2011 48 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:4 3:0 Variable Reserved SETDLY Default 0000 0000 Description Defines the bias settling time for each channel’s subsequent conversion (i.e. when filtering is enabled): 0000 : 0.5 us 0001 : 1.1 us 0010 : 2.2 us 0011 : 4.4 us 0100 : 8.9 us 0101 : 17.8 us 0110 : 35.5 us 0111 : 71.0 us 1000 : 142 us 1001 : 284 us 1010 : 768 us 1011 : 1.14 ms 1100 : 2.27 ms 1101 : 4.75 ms 1110 : 9.09 ms 1111 : 18.19 ms Values above assume typical FOSCH, else vary accordingly. Table 15 : RegTouch2 (Addr 0x02) Bits 7:6 5:3 2:0 Variable Reserved RMSELY RMSELX Default 00 000 000 Bits 7 Variable XCONV Default 1 6 YCONV 1 5 Z1CONV 0 4 Z2CONV 0 3 2 Reserved RXCONV 0 0 1 RYCONV 0 0 Reserved 0 Description Cf. §4.5 Cf. §4.5 Table 16 : RegTouch3 (Addr 0x03) Description Enables X channel conversion: 0 : OFF 1 : ON Enables Y channel conversion: 0 : OFF 1 : ON Enables Z1 channel conversion: 0 : OFF 1 : ON Enables Z2 channel conversion: 0 : OFF 1 : ON Enables RX channel conversion: 0 : OFF 1 : ON Enables RY channel conversion: 0 : OFF 1 : ON Table 17 : RegChanMsk (Addr 0x04) Bits 7 Variable HAPTMODE th Rev 1 – 25 July 2011 Default 0 Description Defines the haptics mode/input: 0 : PWM 1 : I2C 49 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 6:5 HAPTTYPEEN 00 4 HAPTRANGE 0 3:0 HAPTGAIN 0000 Defines the haptics load: 00 : OFF. Haptics block disabled. 01 : LRA 10 : ERM 11 : Reserved Defines MIN prescaler value: 0 : 128 1 : 256 Defines the haptics output gain: 0000 : 1 0001 : ~1.17 0010 : ~1.34 0011 : ~1.51 0100 : ~1.67 0101 : ~1.84 0110 : ~2.01 0111 : ~2.18 1000 : ~2.35 1001 : ~2.52 1010 : ~2.69 1011 : ~2.86 1100 : ~3.03 1101 : ~3.20 1110 : ~3.37 1111 : ~3.53 Exact formula is 1 + Code * 0.169 Table 18 : RegHapt0 (Addr 0x05) Bits 7:6 5:3 Variable Reserved HAPTSQUELCH 2 TEMPWRNIRQEDG 0 1 TEMPALRMIRQEDG 0 0 TEMPALWAYSON 0 th Rev 1 – 25 July 2011 Default 00 000 Description Defines the Haptics squelch, i.e. the range of AmplitudeCode (HAPTAMP or MIN duty cycle equivalent, Cf. §6) which will generate a 0V output (VMOUT): 000 : OFF. No squelch. 001 : -1 < AmplitudeCode < +1 (ie. AmplitudeCode = 0) 010 : -2 < AmplitudeCode < +2 011 : -4 < AmplitudeCode < +4 100 : -8 < AmplitudeCode < +8 101 : -16 < AmplitudeCode < +16 110 : -32 < AmplitudeCode < +32 111 : -64 < AmplitudeCode < +64 Enables TempWrnIrq to be generated when the chip temperature gets below the alarm threshold : 0 : OFF. TempWrnIrq generated only when the chip temperature gets above the alarm threshold. 1 : ON. TempWrnIrq generated both when the chip temperature gets above and below the alarm threshold. Enables TempAlrmIrq to be generated when the chip temperature gets below the alarm threshold : 0 : OFF. TempAlrmIrq generated only when the chip temperature gets above the alarm threshold. 1 : ON. TempAlrmIrq generated both when the chip temperature gets above and below the alarm threshold. Enables the temperature monitoring even when no operation (touch, proximity, haptics) is enabled: 0 : OFF 1 : ON Table 19 : RegHapt1 (Addr 0x06) 50 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:0 Variable HAPTAMP Default 0x00 Description Defines the haptics output polarity and level in I2C mode i.e. AmplitudeCode (Cf. §6) : 0xFF : +127 (Max positive) … 0x81 : +1 0x80 : +0 0x00 : -0 0x01 : -1 … 0x7F : -127 (Max negative) HAPTAMP[7] gives the sign of AmplitudeCode (1=>+;0=>-) while HAPTAMP[6:0] give its magnitude. Table 20 : RegHapt2 (Addr 0x07) Bits 7:5 Variable HAPTBW Default 100 4 HAPTHZ 0 3 HAPTSHORTPROT 0 2:0 HAPTTIMERMSB 000 Bits 7:0 Variable HAPTTIMERLSB Default 0x00 Bits 7:0 Variable Reserved Default 0x00 Description Defines the haptics low-pass filter cut off frequency (Hz): 000 : OFF. No filtering. 001 : ~210 * SamplingFreq / 100 010 : ~280 * SamplingFreq / 100 011 : ~425 * SamplingFreq / 100 100 : ~565 * SamplingFreq / 100 101 : ~700 * SamplingFreq / 100 110 : ~850 * SamplingFreq / 100 111 : ~980 * SamplingFreq / 100 SamplingFreq is VMOUT_Freq in LRA mode and MIN_Freq (PWM) or FOSCL (I2C) in ERM mode (Cf. §6) Sets MOUTP and MOUTN to high impedance (HZ): 0 : Normal 1 : HZ Disables short-circuit protection: 0 : ON . A short-circuit event will automatically stop haptics operation. 1 : OFF. A short-circuit event will not stop haptics operation. In both cases HAPTSHORTSTAT is still updated (and hence an interrupt can still be generated if needed) Defines the haptics timer overflow value used to generate the LRA’s 128 or 256 multiple frequency from MIN. Table 21 : RegHapt3 (Addr 0x08) Description Defines the haptics timer overflow value used to generate the LRA’s 128 or 256 multiple frequency from MIN. HAPTTIMER[9:0] values below 8 (ie 0-7) are reserved. Table 22 : RegHapt4 (Addr 0x09) Description Table 23 : RegHapt5 (Addr 0x0A) Bits 7 6 Variable PROXRAWFILTSEL PROXIRQSEL th Rev 1 – 25 July 2011 Default 0 0 Description Defines the proximity raw filtering range for PROXRAWFILT : 0 : Fast 1 : Slow Defines the function of bits 5 of RegIrqMsk and RegIrqSrc. 0 : ProxFar 1 : ProxConvDone 51 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5:4 PROXHYST 3:0 PROXSCANPERIOD Bits 7:0 Variable PROXTHRESH Default 0x00 Description Defines the proximity detection threshold (for PROXSTAT update). Threshold = 16 x register value Table 25 : RegProx1 (Addr 0x0C) Bits 7:6 Variable PROXCLOSEDEB Default 00 5:4 PROXFARDEB 3:0 PROXCOMPPRD Description Defines the “Close” debounce (for PROXSTAT update): 00 : OFF 01 : 2 samples 10 : 4 samples 11 : 8 samples Defines the “Far” debounce (for PROXSTAT update): 00 : OFF 01 : 2 samples 10 : 4 samples 11 : 8 samples Defines the periodic compensation : 0 : OFF Else : register value x 128 samples Table 26 : RegProx2 (Addr 0x0D) Bits 7:0 Variable PROXSTUCK Bits 7:0 Variable PROXAVGPOSTHRESH th Rev 1 – 25 July 2011 00 0000 00 0000 Default 0x00 Defines the proximity detection hysteresis : 00 : OFF 01 : 32 10 : 128 11 : 512 Defines the proximity scan period : 0000 : OFF. Proximity sensing disabled 0001 : 1 / TOUCHRATE (Cf. RegTouch0) 0010 : 2 / TOUCHRATE 0011 : 4 / TOUCHRATE 0100 : 8 / TOUCHRATE 0101 : 16 / TOUCHRATE 0110 : 32 / TOUCHRATE 0111 : 64 / TOUCHRATE 1000 : 128 / TOUCHRATE 1001 : 256 / TOUCHRATE 1010 : 512 / TOUCHRATE 1011 : 1024 / TOUCHRATE 1100 : 2048 / TOUCHRATE 1101 : 4096 / TOUCHRATE 1110 : 8192 / TOUCHRATE 1111 : 16384 / TOUCHRATE Table 24 : RegProx0 (Addr 0x0B) Description Defines the stuck at timeout (ie max “Close” time before a compensation is automatically requested) : 0 : OFF Else : register value x 16 samples Table 27 : RegProx3 (Addr 0x0E) Default 0x00 Description Defines the average positive threshold (for compensation). Threshold = 8 x register value Table 28 : RegProx4 (Addr 0x0F) 52 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:5 Variable PROXAVGPOSDEB Default 000 4:2 PROXAVGPOSFILT 000 1:0 PROXRAWFILT 00 Bits 7:0 Variable PROXAVGNEGTHRESH Bits 7:5 Variable PROXAVGNEGDEB Default 000 4:2 PROXAVGNEGFILT 000 Description Defines the average positive debounce (for compensation) : 000 : OFF 001 : 2 samples 010 : 4 samples 011 : 8 samples 100 : 16 samples 101 : 32 samples 110 : 64 samples 111 : 128 samples Defines the average positive filter coefficient : 000 : 0 (ie filtering OFF) 001 : 1 – 1/2 010 : 1 – 1/4 011 : 1 – 1/8 100 : 1 – 1/16 101 : 1 – 1/32 110 : 1 – 1/64 111 : 1 – 1/128 Defines the raw filter coefficient. If PROXRAWFILTSEL = 0 : 00 : 0 (ie filtering OFF) 01 : 1 – 1/2 10 : 1 – 1/4 11 : 1 – 1/8 If PROXRAWFILTSEL = 1 : 00 : 1 – 1/16 01 : 1 – 1/32 10 : 1 – 1/64 11 : 1 – 1/128 Table 29 : RegProx5 (Addr 0x10) Default 0x00 Description Defines the average negative threshold (for compensation). Threshold = – 8 x register value Table 30 : RegProx6 (Addr 0x11) 1 PROXHIGHIM 0 0 Reserved 0 Description Defines the average negative debounce (for compensation) : 000 : OFF 001 : 2 samples 010 : 4 samples 011 : 8 samples 100 : 16 samples 101 : 32 samples 110 : 64 samples 111 : 128 samples Defines the average negative filter coefficient : 000 : 0 (i.e. filtering OFF) 001 : 1 – 1/2 010 : 1 – 1/4 011 : 1 – 1/8 100 : 1 – 1/16 101 : 1 – 1/32 110 : 1 – 1/64 111 : 1 – 1/128 Enables high noise immunity mode : 0 : OFF 1 : ON, at the expense of higher power consumption. Table 31 : RegProx7 (Addr 0x12) th Rev 1 – 25 July 2011 53 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:4 3:0 Variable Reserved PROXRAWMSB Default 0000 0000 Bits 7:0 Variable PROXRAWLSB Default 0x00 Bits 7:4 3:0 Variable Reserved PROXUSEFULMSB Default 0000 0000 Bits 7:0 Variable PROXUSEFULLSB Default 0x00 Bits 7:4 3:0 Variable Reserved PROXAVGMSB Default 0000 0000 Bits 7:0 Variable PROXAVGLSB Default 0x00 Bits 7:5 4:0 Variable Reserved PROXDIFFMSB Default 0000 0000 Bits 7:0 Variable PROXDIFFLSB Default 0x00 Description Provides the proximity differential information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 39 : RegProx15 (Addr 0x1A) Bits 7:0 Variable PROXOFFSETMSB Default 0x00 Description Provides the proximity compensation offset information for monitoring purposes. Read-only (using PROXCONVDONE), do not write. Table 40 : RegProx16 (Addr 0x1B) th Rev 1 – 25 July 2011 Description Provides the proximity raw information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 32 : RegProx8 (Addr 0x13) Description Provides the proximity raw information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 33 : RegProx9 (Addr 0x14) Description Provides the proximity information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 34 : RegProx10 (Addr 0x15) Description Provides the proximity information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 35 : RegProx11 (Addr 0x16) Description Provides the proximity average information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 36 : RegProx12 (Addr 0x17) Description Provides the proximity average information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 37 : RegProx13 (Addr 0x18) Description Provides the proximity differential information for monitoring purposes. Signed, 2's complement format. Read-only (using PROXCONVDONE), do not write. Table 38 : RegProx14 (Addr 0x19) 54 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:0 Variable PROXOFFSETLSB Default 0x00 Bits 7 6:4 Variable Reserved PROXSENSITIVITY Default 0 000 3:1 PROXFREQ 0 Reserved 000 Description Provides the proximity compensation offset information for monitoring purposes. Read-only (using PROXCONVDONE), do not write. Table 41 : RegProx17 (Addr 0x1C) Description Defines the sensitivity : 000 : 0 (Min) 001 : 1 010 : 2 011 : 3 100 : 4 101 : 5 110 : 6 111 : 7 (Max) Defines the operating frequency : 010 : 64 kHz 011 : 90 kHz 100 : 112 kHz 101 : 150 kHz (recommended) Else : Reserved 0 Table 42 : RegProx18 (Addr 0x1D) Bits 7:4 Variable PROXSENSORCON Default 0000 Description Defines the proximity sensor connection, Cf. §5.1 : 0000 : None 0001 : AUX1/WIPER (5-wire TS) 0010 : AUX2 (external) 1000 : X (standard 4-wire TS) 1001 : Y (inverted 4-wire TS) Else : Reserved 0000 Defines the proximity shield connection, Cf. §5.1 : 0000 : None 0011 : AUX3 (external) 1000 : X (inverted 4-wire TS) 1001 : Y (standard 4-wire TS or 5-wire TS) Else : Reserved Table 43 : RegProx19 (Addr 0x1E) 3:0 PROXSHIELDCON Bits 7:6 5:3 Variable Reserved PROXBOOST 2:0 Reserved 000 Bits 7:0 Variable Reserved Default 0x01 Bits 7:0 Variable Reserved Default 0x00 Default 00 000 Description Enables proximity boost mode (higher sensitivity) : 100 : ON 110 : OFF (recommended; compulsory when sensor is TS) Else : Reserved Must be set to 100. Table 44 : RegProx20 (Addr 0x1F) Description Must be set to 0x81. Table 45 : RegProx21 (Addr 0x20) Description Table 46 : RegProx22 (Addr 0x21) th Rev 1 – 25 July 2011 55 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7 Variable HAPTSHORTIRQEN 6 PROXCLOSEIRQEN 5 PROXFARIRQEN/ PROXCONVDONEIRQEN 4 PROXCOMPDONEIRQEN 3 PENTOUCHIRQEN/ TOUCHCONVDONEIRQEN 2 PENRELEASEIRQEN 1 TEMPWARNINGIRQEN 0 TEMPALARMIRQEN Bits 7 Variable HAPTSHORTIRQ 6 PROXCLOSEIRQ 5 PROXFARIRQ/ PROXCONVDONEIRQ 4 PROXCOMPDONEIRQ 3 PENTOUCHIRQ/ TOUCHCONVDONEIRQ 2 PENRELEASEIRQ 1 TEMPWARNINGIRQ 0 TEMPALARMIRQ Bits 7 6 Variable HAPTSHORTSTAT RESETSTAT th Rev 1 – 25 July 2011 Default 0 Description Enables the HaptShort interrupt. 0 : OFF 1 : ON 0 Enables the ProxClose interrupt. 0 : OFF 1 : ON 0 Enables the ProxFar/ProxConvDone interrupt. Cf RegProx0[6] 0 : OFF 1 : ON 0 Enables the ProxCompDone interrupt. 0 : OFF 1 : ON 1 Enables the PenTouch/TouchConvDone interrupt 0 : OFF 1 : ON 0 Enables the PenRelease interrupt. 0 : OFF 1 : ON 0 Enables the TempWarning interrupt. 0 : OFF 1 : ON 0 Enables the TempAlarm interrupt. 0 : OFF 1 : ON Table 47 : RegIrqMsk (Addr 0x22) Default 0 Description Gives the HaptShort interrupt source status. (ie HAPTSHORTSTAT rising edge) 0 Gives the ProxClose interrupt source status. (ie PROXSTAT rising edge) 0 Gives the ProxFar (ie PROXSTAT falling edge), or ProxConvDone (ie CONVSTAT falling edge after proximity conversion) interrupt status depending on PROXIRQSEL . 0 Gives the ProxCompDone interrupt source status. (ie PROXCOMPSTAT falling edge) 0 Gives the PenTouch/TouchConvDone interrupt source status. (ie in PENDET mode -> PENSTAT rising edge, else -> CONVSTAT falling edge after touch conversion) 0 Gives the PenRelease interrupt source status. (ie PENSTAT falling edge) 0 Gives the TempWarning interrupt source status. (ie TEMPWARNINGSTAT rising/falling edge depending on TEMPWRNIRQEDG) 0 Gives the TempAlarm interrupt source status. (ie TEMPALARMSTAT rising/falling edge depending on TEMPALRMIRQEDG) Table 48 : RegIrqSrc (Addr 0x23) Default 0 0 Description Gives the haptics short-circuit instantaneous status : 0 : No short circuit is currently present 1 : A short circuit is currently present Gives the reset latched status : 0 : No reset occurred 1 : A reset occurred This bit is cleared when RegStat is read. 56 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 5 PROXSTAT 4 PROXCOMPSTAT 3 CONVSTAT 2 PENSTAT 1 TEMPWARNINGSTAT 0 TEMPALARMSTAT 0 0 When set to ‘1’, triggers a compensation for next scan period. Gives touch/proximity conversion instantaneous status : 0 : No touch or proximity conversion is currently running 1 : A touch or proximity conversion is currently running 0 Gives the pen instantaneous status : 0 : Released/Up 1 : Touching/Down 0 Gives the temperature warning instantaneous status : 0 : Temperature is below warning threshold 1 : Temperature is above warning threshold 0 Gives the temperature alarm instantaneous status : 0 : Temperature is below alarm threshold 1 : Temperature is above alarm threshold Table 49 : RegStat (Addr 0x24) Variable Reserved AUX1DIGOUTEN Default 0 0 5 AUX2DIGOUTEN 0 4 AUX3DIGOUTEN 0 AUX1DIGOUT th Rev 1 – 25 July 2011 PROXSTAT (and PROXAVG) is automatically frozen to its current value if pen is down (whether TS or AUXi is the sensor) PROXSTAT is NOT frozen while haptics is running, if needed host can turn proximity sensing ON/OFF via PROXSCANPERIOD. When read, this bit indicates gives the compensation instantaneous status : 0 : No compensation is currently pending 1 : A compensation is currently pending execution and/or completion 0 Bits 7 6 3:0 Gives the proximity instantaneous status: 0 : Far (or proximity sensing disabled) 1 : Close Description Enables the digital output capability of AUX1 0 : OFF 1 : ON, Cf. AUX1DIGOUT. Bit is ignored if TSTYPE = 1 or PROXSENSORCON = 0001 Enables the digital output capability of AUX2 0 : OFF 1 : ON, Cf. AUX2DIGOUT. Bit is ignored if PROXSENSORCON = 0010 Enables the digital output capability of AUX3 0 : OFF 1 : ON, Cf. AUX3DIGOUT. Bit is ignored if TSTYPE = 1 or PROXSHIELDCON = 0011 Defines the digital signal to output on AUX1 : 0000 : RegIrqSrc(0) 1000 : RegStat(0) 0001 : RegIrqSrc(1) 1001 : RegStat(1) 0010 : RegIrqSrc(2) 1010 : RegStat(2) 0011 : RegIrqSrc(3) 1011 : RegStat(3) 0100 : RegIrqSrc(4) 1100 : RegStat(4) 0101 : RegIrqSrc(5) 1101 : RegStat(5) 0110 : RegIrqSrc(6) 1110 : RegStat(6) 0111 : RegIrqSrc(7) 1111 : RegStat(7) Table 50 : RegAux0 (Addr 0x25) 0000 57 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING Bits 7:4 Variable AUX2DIGOUT 3:0 AUX3DIGOUT Bits 7:0 Variable SOFTRESET th Rev 1 – 25 July 2011 Default 0000 Description Defines the digital signal to output on AUX2 : 0000 : RegIrqSrc(0) 1000 : RegStat(0) 0001 : RegIrqSrc(1) 1001 : RegStat(1) 0010 : RegIrqSrc(2) 1010 : RegStat(2) 0011 : RegIrqSrc(3) 1011 : RegStat(3) 0100 : RegIrqSrc(4) 1100 : RegStat(4) 0101 : RegIrqSrc(5) 1101 : RegStat(5) 0110 : RegIrqSrc(6) 1110 : RegStat(6) 0111 : RegIrqSrc(7) 1111 : RegStat(7) 0000 Defines the digital signal to output on AUX3 : 0000 : RegIrqSrc(0) 1000 : RegStat(0) 0001 : RegIrqSrc(1) 1001 : RegStat(1) 0010 : RegIrqSrc(2) 1010 : RegStat(2) 0011 : RegIrqSrc(3) 1011 : RegStat(3) 0100 : RegIrqSrc(4) 1100 : RegStat(4) 0101 : RegIrqSrc(5) 1101 : RegStat(5) 0110 : RegIrqSrc(6) 1110 : RegStat(6) 0111 : RegIrqSrc(7) 1111 : RegStat(7) Table 51 : RegAux1 (Addr 0x26) Default 0x00 Description Writing 0xDE will reset the chip and all registers to their default values. Table 52 : RegReset (Addr 0x3F) 58 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 13 APPLICATION INFORMATION 13.1 Typical Application Circuit Figure 56 – Typical Application Circuit 13.2 External Components Recommended Values Symbol CVDD CMVDD CVREG RPULL Description Note Min Main supply decoupling capacitor Motor supply decoupling capacitor Regulator decoupling capacitor +/- 20%, ESR<1Ω Host interface pull-ups +/- 50% Proximity sensor-to-shield CTB capacitance RXY Proximity sensor serial resistor RMOT Motor resistance 7.5 CMOUT Motor output capacitor Table 53 : External Components Recommended Values Typ. 1 10 100 10 Max - Unit uF uF nF kΩ <0.7 1.5 nF <1 1 1.5 - kΩ Ω uF 13.3 Multitouch Gestures 13.3.1 Pinch/Stretch A simple thumb and forefinger “pinch” movement enables a user to enlarge objects onscreen (moving fingers away from each other) or make them smaller (move them towards each other). This intuitive zooming function replaces the standard point-and-click functionality of a mouse and provides far greater accuracy to the user. Figure 57 – Pinch/Stretch Multitouch Gestures th Rev 1 – 25 July 2011 59 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 13.3.2 Rotate Objects are rotated onscreen by making simple clockwise (right) or counterclockwise (left) movements with the anchored thumb and forefinger. This multi-touch function enables swift and accurate positioning of objects without needing to point and click repeatedly on a rotate left-right function button in order to achieve the desired effect. Figure 58 – Rotate Multitouch Gestures th Rev 1 – 25 July 2011 60 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 14 PACKAGING INFORMATION 14.1 QFN Package Figure 59 - Outline Drawing - QFN Figure 60 - Land Pattern - QFN th Rev 1 – 25 July 2011 61 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING 14.2 CSP Package Figure 61 - Outline Drawing - CSP Figure 62 - Land Pattern - CSP th Rev 1 – 25 July 2011 62 www.semtech.com SX8677/SX8678 Haptics Enabled Multitouch 4/5-Wire Resistive Touchscreen Controller with Proximity Sensing ADVANCED COMMUNICATIONS & SENSING © Semtech 2011 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. 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