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advanced communications & sensing rev 1 C 25 th july 2011 1 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing g eneral d escription 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 suc h 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, lo w power 12-bit analog-digital converter. on-chip dat a averaging processing algorithms can be activated to reduce host activity and suppress system noise. th e processing core features low power modes which intelligently minimize current in operation as well as in automatic shut-down. multitouch feature enables detection of 2 fingers o n the touchscreen and several gestures like rotation and pinch/stretch. a capacitive proximity detection circuit has been integrated into the sx8677 to enable host controlle d power management for battery applications. proximit y detection above 5 cm is possible using either the resistive touch screen as the sensor or with a sing le conductive plate, with communication to the host vi a 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 th e i2c serial interface, providing simple host interfa cing 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 are a, but also increases application reliability. the three devices have an ambient operating temperature range of -40c to +85c, 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 space- conscious applications. t ypical a pplications game machines, portable music players mobile phones dsc, dvr, phones pos/poi terminals touch-screen monitors o rdering i nformation k ey p roduct f eatures low voltage operation 2.3v to 3.6v supply integrated low drop out (ldo) regulator low power consumption 30ua@2.3v 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 -40c to +85c operating temperature range 15kv hbm & iec esd protection small footprint packages pb & halogen free, rohs/weee compliant part number package marking sx8677iwltrt qfn-20 SX8677ICSTRT wlcsp-19 rnt2 sx8678iwltrt qfn-20 sx8678icstrt wlcsp-19 rp9x sx8674evk evaluation kit - i2c nrst nirq sx8677 host controller multitouch control proximity sensing m haptics driver
advanced communications & sensing rev 1 C 25 th july 2011 2 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing table of contents g eneral d escription ................................................... ................................................... ............... 1 t ypical a pplications ................................................... ................................................... ............... 1 o rdering i nformation ................................................... ................................................... ............. 1 k ey p roduct f eatures ................................................... ................................................... ............ 1 1 g eneral description ................................................... ................................................... ...... 4 1.1 marking information 4 1.1.1 sx8677 4 1.1.2 sx8678 4 1.2 pin diagrams 5 1.2.1 qfn package 5 1.2.2 csp package 5 1.3 pin description 6 1.4 block diagram 6 2 e lectrical c haracteristics ................................................... ............................................ 8 2.1 absolute maximum ratings 8 2.2 thermal characteristics 8 2.3 electrical specifications 8 3 t ypical o perating c haracteristics ................................................... ............................ 11 4 t ouchscreen i nterface ................................................... .................................................. 1 2 4.1 introduction 12 4.2 coordinates measurement 13 4.2.1 4-wire touchscreen 13 4.2.2 5-wire touchscreen 14 4.3 pressure measurement (4-wire only) 14 4.3.1 bias time (powdly) 15 4.4 pen detection 15 4.5 multitouch measurement (4-wire only) 16 4.6 digital processing 17 4.7 host operation 18 4.7.1 overview 18 4.7.2 manual mode (man) 18 4.7.3 pen detect mode (pendet) 20 4.7.4 pen trigger mode (pentrg) 20 4.7.5 maximum throughput vs. touchrate setting 21 5 p roximity s ensing i nterface (sx8677) ........................................... ................................. 23 5.1 introduction 23 5.2 analog front-end (afe) 24 5.2.1 capacitive sensing basics 24 5.2.2 afe block diagram 25 5.2.3 capacitance-to-voltage conversion (c-to-v) 26 5.2.4 shield control 26 5.2.5 offset compensation 26 5.2.6 analog-to-digital conversion (adc) 27 5.3 digital processing 27 5.3.1 overview 27 5.3.2 proxraw update 28 5.3.3 proxuseful update 29 5.3.4 proxavg update 30
advanced communications & sensing rev 1 C 25 th july 2011 3 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5.3.5 proxdiff update 32 5.3.6 proxstat update 32 5.4 host operation 33 5.4.1 general description 33 5.4.2 proximity sensing vs touch operations 33 5.4.3 minimum scan period (i.e. proxscanperiod) 35 6 h aptics i nterface (sx8677/78) ........................................ .................................................. 3 6 6.1 introduction 36 6.2 erm load 36 6.2.1 introduction 36 6.2.2 pwm mode 37 6.2.3 i2c mode 37 6.3 lra load 37 6.3.1 introduction 37 6.3.2 pwm mode 38 6.3.3 i2c mode 38 6.4 short-circuit protection 38 7 t emperature s ensor ................................................... ................................................... .... 39 8 i nterrupt (nirq) ............................................. ................................................... .................. 40 8.1 introduction 40 8.2 registers overview 40 8.2.1 regirqmsk 40 8.2.2 regirqsrc 40 8.2.3 regstat 40 8.3 host procedure 40 9 a uxiliary p ins (aux1/aux2/aux3)................................... ................................................... 41 10 r eset ................................................... ................................................... ................................ 42 10.1 hardware (por and nrst) 42 10.2 software (regreset) 42 10.3 esd event (resetstat) 42 11 i2c i nterface ................................................... ................................................... .................. 43 11.1 introduction 43 11.2 i2c address 43 11.3 write register 43 11.4 read register 44 11.5 write command (touchscreen interface) 44 11.6 read channel (touchscreen interface) 45 12 r egisters d etailed d escription ................................................... ................................... 47 13 a pplication i nformation ................................................... ................................................ 59 13.1 typical application circuit 59 13.2 external components recommended values 59 13.3 multitouch gestures 59 13.3.1 pinch/stretch 59 13.3.2 rotate 60 14 p ackaging i nformation ................................................... .................................................. 6 1 14.1 qfn package 61 14.2 csp package 62
advanced communications & sensing rev 1 C 25 th july 2011 4 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 1 g eneral description 1.1 marking information 1.1.1 sx8677 figure 1 C marking information C qfn(left) C csp(ri ght) 1.1.2 sx8678 figure 2 C marking information C qfn(left) C csp(ri ght)
advanced communications & sensing rev 1 C 25 th july 2011 5 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 1.2 pin diagrams 1.2.1 qfn package figure 3 C pin diagram C qfn 1.2.2 csp package figure 4 C pin diagram - csp
advanced communications & sensing rev 1 C 25 th july 2011 6 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 1.3 pin description name type description vdd p main power supply gnd p main ground vreg p internal regulator output (must be connected to an external capacitor; see 13) mvdd p haptics motor power supply mgnd p haptics motor ground (must be electrically c onnected to gnd) moutp ao haptics motor positive drive moutn ao haptics motor negative drive min di haptics motor pwm/clock input x+/br a 4-wire touchscreen : x+ electrode 5-wire touchscreen : bottom right (br) electrode y+/tr a 4-wire touchscreen : y+ electrode 5-wire touchscreen : top right (tr) electrode x-/tl a 4-wire touchscreen : x- electrode 5-wire touchscreen : top left (tl) electrode y-/bl a 4-wire touchscreen : y- electrode 5-wire touchscreen : bottom left (bl) electrode aux1/wiper d/a 4-wire touchscreen : first programmable auxiliary function (see 9) 5-wire touchscreen : wiper electrode aux2 d/a second programmable auxiliary function (se e 9) aux3 d/a third programmable auxiliary function (see 9) addr di i2c address selection (qfn only, internally connected to gnd on csp) scl di i2c clock input sda dio i2c data input/output nirq do interrupt output (active low) nrst di reset input (active low) a/d/i/o/p: analog/digital/power/input/output table 1 C pin description 1.4 block diagram figure 5 C sx8677 block diagram
advanced communications & sensing rev 1 C 25 th july 2011 7 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 6 C sx8678 block diagram
advanced communications & sensing rev 1 C 25 th july 2011 8 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 2 e lectrical c haracteristics 2.1 absolute maximum ratings stress above the limits listed in the following tab le may cause permanent failure. exposure to absolut e ratings for extended time periods may affect device reliability . the limiting values are in accordance with the ab solute maximum rating system (iec 134). all voltages are r eferenced to ground (gnd). symbol description conditions min max unit vabs voltage applied on any pin - 0.5 3.9 v x+/br, y+/tr, x-/tl, y-/bl, vdd, mvdd +/-15 (1) , +/-8 (2) vesdhbm electrostatic handling human body model (hbm) other pins +/-8 (2) kv x+/br, y+/tr, x-/tl, y-/bl, vdd, mvdd +/-1 vesdcdm electrostatic handling charged device model (cdm) other pins +/-1 kv x+/br, y+/tr, x-/tl, y-/bl, vdd, mvdd +/-250 vesdmm electrostatic handling machine model (mm) other pins +/-250 v vesdcd electrostatic handling contact discharge (cd) x+/br, y+/tr, x-/tl, y-/bl, vdd, mvdd +/-15 kv tamb operating ambient temperature -40 +85 c tjun operating junction temperature -40 +125 c tstor storage temperature -55 +150 c ilat latch-up current (3) +/-100 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 symbol description conditions min max unit jaq thermal resistance junction C ambient qfn package - - 30.5 c/w jaw thermal resistance junction C ambient wlcsp package - - 29 c/w table 3 C thermal characteristics 2.3 electrical specifications table below applies to full supply voltage and temp erature range, unless otherwise specified. typical values are given for t a = +25c, vdd=vddm=3.3v. symbol description conditions min typ. max unit supply vdd main supply voltage - 2.3 - 3.6 v off (man mode, no command, hapt off) - 0.4 0.75 wait (pendet/trg mode, pen up, prox off, hapt off) - 1.7 - touch1 (pentrg mode, pen down , x+y, rate=4kcps, nfilt=1, powdly=0.5us, touchscreen current excluded, hapt off, vdd=2.3v) - 30 - idd main supply current touch2 (pentrg mode, pen down , x+y, rate=3kcps, nfilt=7, powdly=0.5us, touchscreen current excluded, hapt off) - 120 160 ua
advanced communications & sensing rev 1 C 25 th july 2011 9 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing symbol description conditions min typ. max unit prox (pendet/trg mode, pen up, touchrate=80cps, prox on, scanperiod=200ms, highim=on, sensitivity=max, freq=150khz, boost=off, hapt off) - 8 20 hapt (man mode, no command, lra-pwm mode, min= 44.8khz/50%, gain = max, bw = 100, moutp/n floating, squelch=011) - 115 145 mvdd haptics supply voltage - vdd - 3.6 v off - 0.01 1 a midd haptics supply current squelch (lra-pwm mode, min= 44.8khz/50%, gain = max, bw = 100, moutp/n floating, squelch=011) - 6 10 a digital i/os (addr, scl, sda, nrst, nirq, aux1, aux 2, aux3, min) scl, sda, nrst 0.8*vdd - 3.6 vih high level input voltage other pins 0.8*vdd - vdd+0.2 v vil low level input voltage - -0.3 - 0.8 v ileak input leakage current - -1 - 1 a ci input capacitance - - 5 - pf voh high level output voltage ioh = 4ma 0.8*vdd - - v vol low level output voltage iol = 4ma - - 0.4 v vpull external pull-up voltage scl, sda, nrst, nirq - - 3.6 v haptics interface idrv maximum drive current (moutp/moutn) mvdd = 3.6v - 250 - ma voff output squelch differential error (from 0v ideal) lra or erm, pwm or i2c, amplitudecode within squelch range, gain = max, bw = 100, moutp/n floating, squelch=011 0 (1) 0 0 (1) mv verr output differential error (from 1.135v ideal) lra or erm, i2c, amplitudecode = +127 (max) gain = min, bw = 100, moutp/n floating 125 (2) 0 125 (2) mv vdrv drive voltage (moutp/moutn) - - - vddm v vdrop drop voltage (moutp/moutn) from mvdd/mgnd, @250ma - - 150 mv ishort short-circuit detection current measured @m idd - 300 - ma fminc motor input (min) frequency in i2c mode 40-60% duty cycle - - 50 mhz haptrange = 0 12.8 - 25.6 khz fminp motor input (min) frequency in pwm mode haptrange = 1 25.6 - 51.2 khz dcmin motor input (min) duty cycle in pwm mode 2 - 98 % twrng warning temperature - 120 - talrm alarm temperature junction temperature - 155 - c touchscreen interface ares adc resolution 12 - - bits aoff adc offset - 1 - age adc gain error at full scale - 0.5 - adnl adc differential non-linearity - 1 - ainl adc integral non-linearity - 1.5 - lsb rbias biasing resistance - 5 - proximity sensing interface cdc external capacitance to be compensated - - - 300 pf t prox scan period (reaction time) programmable - 200 - m s
advanced communications & sensing rev 1 C 25 th july 2011 10 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing symbol description conditions min typ. max unit reset vpor power-on-reset voltage cf. 10 - 1.3 - v t reset reset time after por cf. 10 - - 1 ms t pulse reset pulse from host uc cf. 10 1 - - us i2c interface f scl scl clock frequency - - - 400 khz t hd;sta hold time (repeated) start condition - 0.6 - - s t low low period of the scl clock - 1.3 - - s t high high period of the scl clock - 0.6 - - s t su;sta set-up time for a repeated start condition - 0.6 - - s t hd;dat data hold time - 0 - - s t su;dat data set-up time - 100 - - ns t r rise time of both sda and scl - 20+0.1c b - 300 ns t f fall time of both sda and scl - 20+0.1c b - 300 ns t su;sto set-up time for stop condition - 0.6 - - s t buf bus free time between a stop and start condition - 1.3 - - s c b capacitive load for each bus line - - - 400 pf t sp pulse width of spikes suppressed by the input filter up to 0.3xvdd from gnd, down to 0.7xvdd from vdd 50 - - ns miscellaneous foscl low frequency internal oscillator - - 32 - khz fosch high frequency internal oscillator - - 1.8 - mhz (1) guaranteed by design. (2) pwm mode can introduce an additional error of 2.5% of full scale. table 4 C electrical specifications
advanced communications & sensing rev 1 C 25 th july 2011 11 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 3 t ypical o perating c haracteristics conditions as defined in 2.3, t a = +25c, vdd=vddm=3.3v unless otherwise specified. idd_off vs vdd vs temp 2.00e-07 2.20e-07 2.40e-07 2.60e-07 2.80e-07 3.00e-07 3.20e-07 3.40e-07 3.60e-07 3.80e-07 4.00e-07 2.3 2.5 2.7 2.9 3.1 3.3 3.5 vdd(v) idd(a) 25c 85c -40c idd_wait vs vdd vs touchrate 0 1 2 3 4 5 6 7 8 2.3 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 vdd(v) idd(ua) 10cps 80cps 2000cps 5000cps idd_prox vs scanperiod vs sensitivity 0 10 20 30 40 50 60 70 80 0 100 200 300 400 500 600 700 800 scanperiod(m s) idd_prox(ua) 0(min) 5 7(max) idd_hapt vs vdd vs temp 0.0001 0.00011 0.00012 0.00013 0.00014 0.00015 0.00016 0.00017 0.00018 0.00019 0.0002 2.3 2.5 2.7 2.9 3.1 3.3 3.5 vdd(v) idd(a) 25c 85c -40c midd_off vs mvdd vs temp 0.00e+00 5.00e-09 1.00e-08 1.50e-08 2.00e-08 2.50e-08 3.00e-08 3.50e-08 4.00e-08 4.50e-08 5.00e-08 2.3 2.5 2.7 2.9 3.1 3.3 3.5 mvdd(v) midd(a) 25c 85c -40c midd_squelch vs mvdd vs temp 5.00e-06 6.00e-06 7.00e-06 8.00e-06 9.00e-06 1.00e-05 2.3 2.5 2.7 2.9 3.1 3.3 3.5 mvdd(v) idd(a) 25c 85c -40c verr vs gain vs mvdd 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 gain voff(v) 2.3v 3.3v 3.6v
advanced communications & sensing rev 1 C 25 th july 2011 12 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 4 t ouchscreen i nterface 4.1 introduction the purpose of the touchscreen interface is to meas ure 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 chips touchscreen interfa ce is compatible with both 4-wire and 5-wire touchs creens. touchscreen type is defined by parameter tstype. figure 7 C touchscreen interface overview a 4-wire resistive touch screen consists in two (re sistive) conductive sheets separated by an insulato r when not pressed. each sheet is connected through 2 electrod es at the border of the sheet. when a pressure is a pplied on the top sheet, a connection with the lower sheet is established. figure 8 C 4-wire touchscreen a 5-wire resistive touch screen consists in two (re sistive) conductive sheets separated by an insulato r when not pressed. 4 electrodes are connected on the 4 corner s of the bottom conductive sheet. they are referred as top left (tl), top right (tr), bottom left (bl) and bot tom right (br). the fifth wire (wiper) is used for sensing the top sheet voltage. when a pressure is applied on the to p sheet, a connection with the lower sheet is established.
advanced communications & sensing rev 1 C 25 th july 2011 13 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing higher reliability and better endurance are the adv antages of 5-wire touchscreens but they do not allo w pressure measurement figure 9 C 5-wire touchscreen 4.2 coordinates measurement 4.2.1 4-wire touchscreen the electrode plates are internally connected throu gh terminals x+, x- and y+, y- to an analog to digi tal converter (adc) and a reference voltage (vref). the resistance between the terminals x+ and x- is defi ned by rxtot. rxtot will be split in 2 resistors, r1 and r 2, in case the screen is touched. similarly, the re sistance between the terminals y+ and y- is represented by r 3 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 resis tive sheet (y) is biased with a voltage source (vre f). resistors r3 and r4 determine a voltage divider proportional to the y position of the contact point. since the c onverter has a high input impedance, no current flows through r1 (and rt) so that the voltage x+ at the converter i nput is given by the voltage divider created by r3 and r4. the x coordinate is measured in a similar fashion w ith 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 b y the contact area of the x and y resistive sheet and var ies with the applied pressure. figure 10 C 4-wire touchscreen coordinates measurem ent the x and y positions output by the adc correspond to the formulas below: xpos 4095 r2 r1 r2 + --------------------- = y pos 4095 r4 r3 r4 + --------------------- = 4095 corresponds to the max output value of the adc (12 bits => 2 12 C 1). for example, a touch in the center of the screen wi ll output (xpos, ypos) = ~(2048, 2048)
advanced communications & sensing rev 1 C 25 th july 2011 14 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 4.2.2 5-wire touchscreen 5-wire touchscreen coordinates measurement is perfo rmed 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 a dc. figure 11 C 5-wire touchscreen coordinates measurem ent the x and y positions output by the adc correspond to the formulas below: xpos 4095 r2 r1 r2 + --------------------- = y pos 4095 r4 r3 r4 + --------------------- = 4095 corresponds to the max output value of the adc (12 bits => 2 12 C 1). for example, a touch in the center of the screen wi ll output (xpos, ypos) = ~(2048, 2048) 4.3 pressure measurement (4-wire only) the pressure measurement consists in extracting the touch resistance r t via two additional setups z1 and z2 illustrated below. the smaller r t , the more common touched surface there is between top and bottom plates and hence the more pressure there is by the user. figure 12 C pressure measurement the z1 and z2 values output by the adc correspond t o the formulas below: z1 4095 r4 r1 r4 r t + + ---------------------------------- = z2 4095 r4 rt + r1 r4 r t + + ---------------------------------- = the x and y total sheet resistance (rxtot = r1+r2, rytot = r3+r4) are known from the touch screen supp lier. r4 is proportional to the y coordinate and its valu e is given by the total y plate resistance rytot mu ltiplied by the fraction of the y position over the full coordinate range.
advanced communications & sensing rev 1 C 25 th july 2011 15 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing rxtot r1 r2 + = rytot r3 r4 + = r4 rytot ypos 4095 ------------- = z2 re-arranging z1 and z2 gives: r t r4 z2 z1 ------ 1C = this finally results in: r t rytot ypos 4095 ------------- z2 z1 ------ 1 C = the touch resistance calculation above hence requir es three channel measurements (ypos, z2 and z1) and one specification data (rytot). an alternative calculation method is using xpos, yp os, one z channel and both rxtot and rytot as shown in the next calculations. r1 is inversely proportional to the x coordinate: r1 rxtot 1 xpos 4095 ------------- C = substituting r1 and r4 into z1 and rearranging term s gives: r t rytot y pos 4095 --------------------------------- 4095 z1 ------------ 1C rxtot 1 xpos 4095 ------------- C C = please note that the chip only outputs z1, z2, etc. the calculation of r t 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 prop er vref bias level before the conversion is actually perfor med. it is a function of the pcb trace resistance c onnecting 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 rea ch 12 bits accuracy. adding a capacitor from the touch screen electrodes to ground may also be used to minimize external no ise (if the touchscreen is used as the proximity sensor, ma ke sure you do not exceed the maximum capacitive lo ad for required for proper proximity sensing operation). t he low-pass filter created with the capacitor may i ncrease 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 dete ction prior to conversion avoids feeding the host w ith dummy data and saves power. pen detection is also u sed to disable and resume proximity sensing. for mo re 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 flo w 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 d ivider determined by rpndt and the sum of r1, rt an d r4.
advanced communications & sensing rev 1 C 25 th july 2011 16 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 13 C 4-wire touchscreen pen detection when using a 5-wire touchscreen, the pen detection pull-up resistor r pndt and digital comparator continue to monitor the x+/br pin as in 4-wire mode. the top pa nel is grounded via the wiper pin to provide the gr ounding 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 r pndt and the sum of r1, rt and rw. figure 14 C 5-wire touchscreen pen detection r pndt can be configured to 4 different values to accommo date different screen resistive values. r pndt should be set to a value greater than 7x(rxtot + r ytot), 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 dete ction on panels with high resistance. a pen touch will set the penstat bit of the regstat register which will generate an interrupt if enabl ed in regirqmsk. a pen release will reset penstat bit of the regstat register which will generate an interrupt if enabl ed 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 fig ure below.
advanced communications & sensing rev 1 C 25 th july 2011 17 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing rxtot r1 r2 r3 + + = rytot r4 r5 r6 + + = figure 15 C dual-touch simplified model the two contacts create touch resistances rt1 and r t2 between the two layers of the touchscreen. the sx8677/78 perform on-chip specific multitouch m easurements which the host retrieves and processes with a specific software enabling the detection of the g estures described in 13.3. for optimum gesture detection, rmselx and rmsely pa rameters should be set according to table below. x/y panel resistance ( ) 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 C rmselx/y selection table 4.6 digital processing the chip offers 4 types of data processing which al lows the user to make trade-offs between data throu ghput, power consumption and noise rejection. the parameter filt is used to select the filter ord er 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. - = - ? 1 0 1 n i i n n s n c figure 16 C digital processing block diagram
advanced communications & sensing rev 1 C 25 th july 2011 18 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing filt nfilt function 0 1 c n s n = no average. 1 3 c n 1 3 --- 4079 4095 ------------ s n s n 1C s n 2C + + ( ) = 3 adc samples are averaged. 2 5 c n 1 5 --- 4079 4095 ------------ s n s n 1C s n 2C s n 3C s n 4C + + + + ( ) = 5 adc samples are averaged. 3 7 s max 1 s m ax2 s a s b s c s min 1 s m in 2 3 3 3 3 3 3 c n 1 3 --- 4079 4095 ------------ s a s b s c + + ( ) = 7 adc samples are sorted and the 3 center samples a re averaged. table 6 C digital processing functions the parameter setdly sets the settling time between the consecutive conversions of the same channel. figure 17 C powdly and setdly (filt=2) in most applications, setdly can be set to minimum (0.5us). however, in some particular applications w here 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 configu red 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 s topped and conversions must be manually triggered b y the host using select and convert command.
advanced communications & sensing rev 1 C 25 th july 2011 19 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing when a command is received, the chip executes the a ssociated tasks listed in table below and waits for the next command. it is up to the host to sequence all actio ns. pen detection is performed after each convert comma nd and if pen is not detected, no touch operation i s performed. following figures assume pen down. penst at is not updated in man mode. to enter man mode the host must send the man comman d 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 C manual mode commands as illustrated in figure below the convert command will bias the channel, wait for the programmed sett ling time (powdly), and run the conversion. figure 18 C manual mode C convert command (chan = y ; proxscanperiod = 0) when the convert command is used with chan=seq, mul tiple channels as defined in regchnmsk are sampled. in this case, each channel will be sequent ially biased during powdly before a conversion is s tarted. at the end of each channel conversion the bias is a utomatically removed. figure 19 C manual mode C convert command (chan = s eq = [x;y]; proxscanperiod = 0) in case the range of powdly settings available is n ot enough to cover the required settling time, one can use the select command first to bias the channel, and t hen send the convert command hence extending bias time. select command cannot be used with chan=seq. i2c channel bias convert(seq) channel conversion read channel powdly powdly y y x x nirq (regirqmsk[3]=1) convstat i2c channel bias convert(y) channel conversion read channel nirq (regirqmsk[3]=1) powdly y y convstat select(y) i2c channel bias convert(y) channel conversion read channel y y powdly nirq (regirqmsk[3]=1) a ctual bias time convstat
advanced communications & sensing rev 1 C 25 th july 2011 20 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 20 C manual mode C select command (chan = y; proxscanperiod = 0) at the end of the conversion(s) bit convstat will b e reset which will trigger nirq falling edge (if en abled in regirqmsk). host can then read channel data which w ill release nirq. please note that when the select command is used, t he 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, regular ly as defined by touchrate when pen is down) and update p enstat 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 interf ace the host must enter man mode. figure 21 C pen detect mode (regirqmsk[3:2] = 11 ; proxscanperiod = 0) please note that the next pen detection is not perf ormed as long as nirq is low. if the host is too sl ow and doesnt 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, regular ly as defined by touchrate when pen is down) and if pen i s down, will be followed by a conversion as defined in regchanmsk. the chip will update convstat bit in re gstat and will be able to generate an interrupt (ni rq) upon conversion completion. the chip will also upda te penstat bit in regstat and will be able to gener ate 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 a nd then send pentrg command. to quit pentrg mode and stop the touchscreen interface the host mu st enter man mode. idle pen d etection nirq i2c read reg irqsrc pen touch pen release penstat convstat touchrate tick
advanced communications & sensing rev 1 C 25 th july 2011 21 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 22 C 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 reg chanmsk) have not been read. if the host is too slo w and doesnt 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 d efine the required coordinates throughput/rate. however, as previously mentioned, in order for a ne w conversion to be performed the current conversion must be completed and all relevant channel data must hav e been read by the host. if this condition is not m et when the next touchrate tick occurs, the tick is ignored and the condition checked again at the next one. t his will result in reduced actual rate vs what has been prog rammed in the touchrate parameter. this is illustrated in figures below. figure 23 C correct touchrate setting idle touch conver sion pen detection nirq pen touch pen release i2c read channel penstat convstat touchrate tick idle touch conver sion pen detection nirq touchrate tick i2c read channel tconv tcom trate = tconv + tcom < trate => actual rate = touchrate
advanced communications & sensing rev 1 C 25 th july 2011 22 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 24 C incorrect (too high) touchrate setting in order to prevent this, one can estimate the maxi mum throughput achievable and set touchrate paramet er accordingly. maxthroughput = 1 / (tconv+tcom) tcom is the time between the end of conversion (ie nirq falling edge) and the end of channel data read ing (i.e. nirq rising edge). maximum throughput implies that the host reacts instantaneously to nirq falling e dge: t c om 8 16 n cha n + ( ) t i 2c = tconv is the total conversion time: tconv us ( ) 47 tos c n + c han p owd ly n f ilt 1 C ( ) setd ly 21n filt 1 + ( ) tos c + + ( ) = - t i2c is the period of the i2c clock scl - n filt = {1,3,5,7} based on the order defined for the fil ter filt - n chan = {1,2,3,4,5} based on the number of channels defi ned in regchanmsk - powdly = 0.5us to 18.19ms, settling time as defin ed in regts0 - setdly = 0.5us to 18.19ms, settling time when fil tering as defined in regts2 - tosc is the period of the internal oscillator fos ch some examples of maximum throughputs achievable wit h 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 C maximum throughputs examples - cr = coordinate rate - ecr = equivalent coordinate rate = cr x n chan - sr = sampling rate = cr x n filt - esr = equivalent sampling rate = sr x n chan = cr x n filt x n chan for proper operation, the touchrate parameter shoul d not exceed the theoretical maximum throughput cr. idle touch conver sion pen detection nirq touchrate tick not ready, tick ignored i2c read channel tconv tcom trate = trate < tconv + tcom < n. trate => actual rate = touchrate/n
advanced communications & sensing rev 1 C 25 th july 2011 23 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5 p roximity s ensing i nterface (sx8677) 5.1 introduction the purpose of the proximity sensing interface is t o detect when a conductive object (usually a body p art i.e. finger, palm, face, etc) is in the proximity of the system. this is commonly used in power-sensitive m obile applications to turn the screens lcd on/off depend ing on users finger/palm/face proximity. the chips proximity sensing interface is based on capacitive sensing technology and shares the adc wi th the touchscreen interface (cf 5.4.2). an overview is given in figure below. shield sensor analog frontend (afe) digital processing sx8677 proxstat 0 1 0 finger,palm, face,etc figure 25 C 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 imp rove its global performance. it also brings directi vity to the sensing, for example sensing objects approac hing 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. s ee 5.2 for more details. the digital processing block computes the raw capa citance measurement from the afe and extracts a binary information proxstat corresponding to the pr oximity status, i.e. object is far or close. it also triggers afe operations (compensation, etc). s ee 5.3 for more details. to save power since the proximity event is slow by nature, the block will be waken-up regularly at eve ry programmed scan period (proxscanperiod) to sense an d then process a new proximity sample. the block will be in idle mode most of the time. this is illu strated in figure below figure 26 C proximity sensing sequencing
advanced communications & sensing rev 1 C 25 th july 2011 24 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 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. a s mentioned above, the chips proximity sensing inter face 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 t o understand its basic principles. to illustrate the principle of capacitive sensing w e will use the simplest implementation where the se nsor is a copper plate on a pcb but the exact same principles apply if the sensor is the touchscreens top plate . the figure below shows a cross-section and top view of a typical capacitive sensing implementation. t he sensor connected to the chip is a simple copper area on to p layer of the pcb. it is usually surrounded (shiel ded) by ground for noise immunity (shield function) but als o indirectly couples via the grounds areas of the r est of the system (pcb ground traces/planes, housing, etc). fo r obvious reasons (design, isolation, robustness ) the sensor is stacked behind an overlay which is usuall y integrated in the housing of the complete system. when the touchscreen is used for sensing the overlay corresp onds to the thin and flexible protection film cover ing the top panel. pcbdielectric ground cutview topview pcbcopper sensor overlay figure 27 C typical capacitive sensing implementati on when the conductive object to be detected (finger/p alm/face, etc) is not present, the sensor only sees an inherent capacitance value c env created by its electrical fields 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 sens or increased by the user capacitance c user . this phenomenon is illustrated in the figure below. figure 28 C proximity effect on electrical field an d sensor capacitance
advanced communications & sensing rev 1 C 25 th july 2011 25 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing the challenge of capacitive sensing is to detect th is relatively small variation of c sensor (c user usually contributes for a few percents only) and differentiate it from environmental noise (c env also slowly varies together with the environment characteristics like temperature, etc). for this purpose, the chip integrates an auto offs et compensation mechanism which dynamically monitors a nd removes the c env component to extract and process c user only. see 5.2.5 for more details. in first order, c user can be estimated by the formula below: a is the common area between the two electrodes henc e the common area between the users finger/palm/fa ce and the sensor. d is the distance between the two electrodes hence t he proximity distance between the user and the syst em. 0 is the free space permittivity and is equal to 8.8 5 10e-12 f/m (constant) r is the dielectric relative permittivity. when performing proximity sensing the dielectric re lative permittivity is roughly equal to that of the air as the overlay is relatively thin compared to the detectio n distance targeted. typical permittivity of some c ommon materials is given in the table below. material typical r glass 8 fr4 5 acrylic glass 3 wood 2 air 1 from the discussions above we can conclude that the most robust and efficient design will be the one t hat minimizes c env value and variations while improving c user . 5.2.2 afe block diagram figure 29 C analog front-end block diagram d a c r user 0 =
advanced communications & sensing rev 1 C 25 th july 2011 26 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5.2.3 capacitance-to-voltage conversion (c-to-v) proxsensorcon defines which pin will act as the sen sor during proximity sensing operations. in the typ ical case, the touchscreen top layer is used as the sens or (exact pin/electrode depends on screen type/stru cture). else, the sensor can also be external, i.e. conne cted to aux2. the sensitivity of the interface is defined by prox sensitivity; 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 externa l, proxboost can be set to allow higher sensitivit y if needed. proxfreq defines the operating frequency of the int erface and should be set as high as possible for po wer 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 shi eld during proximity sensing operations. in the typ ical case, the shield will usually be the touchscreen bo ttom layer (exact pin/electrode depends on screen type/structure). else, the shield can also be exte rnal, ie a simple copper area on the pcb connected to aux3. 5.2.5 offset compensation offset compensation consists in performing a one ti me measurement of c env and subtracting it to the total capacitance c sensor in order to feed the adc with the closest contribu tion of c user only. figure 30 C offset compensation block diagram the adc input c user is the total capacitance c sensor to which c env 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 C compensation request sources
advanced communications & sensing rev 1 C 25 th july 2011 27 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing block startup: a compensation is automatically requested when the proximity sensing is enabled via proxscanperiod. i2c: a compensation can be manually requested anytime b y the host through i2c interface. proxavg update: a compensation can be automatically requested if i t is detected that c env 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 i t 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 alway s done at the beginning of a scan period to keep all paramete rs 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 inf ormation into a digital 12-bit word proxraw. the adc is shared with the touchscreen interface us ing 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 fl ag (proxstat) indicating if the users finger/hand/ head is close to the proximity sensor. the offset compensation performed in the afe is a o ne time measurement. however, the environment capacitance c env may vary with time (temperature, nearby objects, e tc). hence, in order to get the best estimation of c user (proxdiff) it is needed to dynamically track and s ubtract c env variations. this is performed by filtering proxuseful to extract its slow variati ons (proxavg). proxdiff is then compared to user programmable thre shold to extract proxstat flag. figure 32 C digital processing block diagram digital processing sequencing is illustrated in fig ure below. at every scan period wake-up (defined by proxscanperiod), the block updates sequentially pro xraw, proxuseful, proxavg, proxdiff and proxstat before going back to idle mode.
advanced communications & sensing rev 1 C 25 th july 2011 28 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 33 C 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.
advanced communications & sensing rev 1 C 25 th july 2011 29 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 34 C proxraw update 5.3.3 proxuseful update proxuseful update consists in filtering proxraw upf ront to remove its potential high frequencies components(system noise, interferer, etc) and extra ct only user activity (few hz max) and slow environ ment changes. figure 35 C proxuseful update f(proxraw ; proxuseful[n-1] ; proxrawfilt) = (1 - p roxrawfilt).proxraw + proxrawfilt.proxuseful[n-1]
advanced communications & sensing rev 1 C 25 th july 2011 30 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 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 enviro nment capacitance c env . one can program positive and negative debounced thr esholds (proxavgposthresh/proxavgposdeb and proxavgnegthresh/proxavgnegdeb) within which pr oxavg 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 negativ e values are considered abnormal and should be compen sated quickly. for this purpose, the averaging filt er coefficient can be set independently for positive a nd 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 activi ty (should only reflect environmental changes) it i s freezes when proximity is detected. figure 36 C proxavg vs proximity event
advanced communications & sensing rev 1 C 25 th july 2011 31 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 37 C proxavg update f(proxuseful ; proxavg[n-1] ; proxavgxxxfilt) = (1 - proxavgxxxfilt).proxuseful + proxavgxxxfilt.proxa vg[n-1] xxx = pos or neg
advanced communications & sensing rev 1 C 25 th july 2011 32 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5.3.5 proxdiff update proxdiff update consists in the complementary opera tion i.e. subtracting proxavg to proxuseful to ignore slow capacitances variations (c env ) and extract only the user related variations i.e. c user . figure 38 C proxdiff update 5.3.6 proxstat update proxstat update consists in taking proxdiff informa tion (c user ), 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 averagi ng and hence absorbed into c env . figure 39 C proxstat update
advanced communications & sensing rev 1 C 25 th july 2011 33 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5.4 host operation 5.4.1 general description if proxirqsel = 0, an interrupt can be triggered wh en the user is detected to be close, detected to be far, or both (proxcloseirqen, proxfarirqen). figure 40 C proximity sensing host operation (pen t rigger mode ; regirqmsk[6:4] = 110 ; proxirqsel = 0 ) if proxirqsel = 1, instead of the proximity far s tate, an interrupt can be triggered at the end of e ach proximity sensing operation indicating to the host when the proximity sensing block is running (proxconvdoneirqen). this may be used by the host t o synchronize noisy system operations or to read proxraw, proxuseful, proxavg, proxdiff synchronousl y for monitoring purposes. figure 41 C proximity sensing host operation (pen t rigger mode ; regirqmsk[6:4] = 010 ; proxirqsel = 1 ) in both cases above, an interrupt can also be trigg ered at the end of compensation (proxcompdoneen). 5.4.2 proximity sensing vs touch operations as previously mentioned, touch and proximity operat ions share the same adc and hence the chip implemen ts time multiplexing between these two types of operat ions. also, proximity sensing doesnt need to be pe rformed while pen is down (not needed as host knows already something touches the screen). in all operating modes, if proxscanperiod = 0, no p roximity operation is performed (i.e. 4.7). the following hence assumes proxscanperiod != 0. for simplicity w e also assume that nirq is only used for reporting touch operations i.e. regirqmsk[6:4] = 000 (proxsta t 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 pen detection nirq i2c read regirqsrc proximity sensing (analog + digital) proxstat convstat proxscanperiod tick user in range user out of range pen detection nirq i2c read regirqsrc proximity sensing (analog + digital) proxstat convstat proxscanperiod tick user i n range user out of range
advanced communications & sensing rev 1 C 25 th july 2011 34 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing touchscreen is used as the proximity sensor and is being touched when the conversion is performed, the proximity measurement result may be incorrect. figure 42 C manual mode C convert command (chan = y ; proxscanperiod != 0; pen down) if the screen is not touched, only the proximity se nsing operation is performed. figure 43 C manual mode C convert command (chan = y ; proxscanperiod != 0, pen up) in pendet and pentrg mode, a proximity sensing oper ation will be performed regularly as defined in proxscanperiod, but only if pen is not detected. figure 44 C pen detect mode (regirqmsk[6:2] = 00011 ; proxscanperiod = 001 ie 1/touchrate) i2c channel bias convert y channel conv e rsion read channel prox nirq (regirqmsk[6:3]=0001) convstat idle touch conver sion pen detection nirq pen touch pen release i2c read regirqsrc proximity sensing convstat penstat touchrate tick i2c channel bias convert y channel conv e rsion read channel powdly y y prox nirq (regirqmsk[6:3]=0001) convstat
advanced communications & sensing rev 1 C 25 th july 2011 35 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 45 C pen trigger mode (regirqmsk[6:2] = 0001 0 ; 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 proximit y sensing operations to be completed, the rate tick(s) affected are ignored until operations are completed and the following t ick is taken into account for the next planned operation. please note that compensation lasts about ~16 times longer than a normal proximity sensing operation. idle touch conv er sion pen detection nirq touchrate tick pen touch pen release i2c read channel proximity sensing penstat convstat
advanced communications & sensing rev 1 C 25 th july 2011 36 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 6 h aptics i nterface (sx8677/78) 6.1 introduction haptics technology is commonly used in systems whic h include a touchscreen interface. its purpose is t o provide tactile feedback to the user to acknowledge a touch event hence improving greatly the robustness of th e 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 perform ed without any external component due to fully embe dded analog processing and with very limited host intera ction due to the embedded digital processing block. figure 46 C haptics interface overview the host configures drive parameters from the i2c p ort 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 p in, min, which accepts a pulse-width-modulated (pwm) digital signa l; or by writing the desired output level directly to a register via the i2c interface. this digital information is filtered to prevent fas t 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 sig nal 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 s upply 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 cr eate a vibration. speed and direction are controlle d by the applied voltage. the erm load is selected when hap ttypeen = 10.
advanced communications & sensing rev 1 C 25 th july 2011 37 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing a c c e l e r a t i n g figure 47 C erm drive signal example if amplitudecode is within haptsquelch range (for m ore 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 depen ding on the mode selected (pwm or i2c), see below. please note that whatever setting, vmout is physica lly 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, inte rnally sampled at foscl). min is not used and shoul d 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-magneti c coil to move the mass. it is operated by applying an ac signal at its resonant frequency (typ. ~175 hz). li ke pushing a swing at its resonance, it doesnt nee d much energy to keep it going, so drive current requireme nts are much lower than for erms. lras have moderat ely high q factors so that the drive frequency must mat ch the resonant frequency within a few hz to get op timum amplitude. lra load is selected when hapttypeen = 01.
advanced communications & sensing rev 1 C 25 th july 2011 38 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing figure 48 C lra drive signal example the carrier frequency of vmout_freq is defined as f ollowing: vmout_freq(hz) = (min_freq / haptrange) (pwm mode) or vmout_freq(hz) = (min_freq / haptrange) / (hapttime r +1) (i2c mode) if amplitudecode is within haptsquelch range (for m ore than 512/vmout_freq): vmout_envelope = 0v else: vmout_envelope(v) = (amplitudecode / 127) x 1.135 * haptgain amplitudecode (signed) is defined differently depen ding on the mode selected (pwm or i2c), see below. please note that whatever setting, vmout is physica lly 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, inte rnally sampled at min_freq). min is still used to e xtract vmout carrier frequency. 6.4 short-circuit protection the haptics interface integrates a short-circuit pr otection circuit which detects when midd is abnorma lly high i.e. above ishort. under a short-circuit event (haptsho rtstat=1) the haptics block will stop operation (moutn & moutp grounded). when the short-circuit is removed the haptics operations will resume normall y.
advanced communications & sensing rev 1 C 25 th july 2011 39 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 7 t emperature s ensor the chip includes a temperature sensor which monito rs the chips junction temperature. its purpose is to provide over-temperature information to the host and if nee ded automatically shutdown chip operation for therm al protection. figure 49 C temperature sensor overview if tempalwayson = 0 (default), the temperature sens or will perform measurements only if the chip is ac tive 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 al ways perform a measurement every ~32 ms independently from chip activity (i.e. also when th e chip is inactive and during adc conversions). each measurement is compared with two internally ha rd-coded thresholds: warning level: typ. 120c (twrng). alarm level: typ. 155c (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. tempe rature > alarm level) all chip operations (i.e. tou chscreen, proximity, haptics) are automatically shutdown unti l the temperature goes below the alarm level. after a shutdown event all stored conversion data a re thrown away. cycling operations (touchrate > 0) will resume from the start (i.e. if a 4 channel conversi on is stopped during the 3 rd channel conversion, when resuming, the 4 channels will be converted again). if the user was running some manual operation (sele ct, convert), the corresponding command will have to be re-issued. the haptics operations will resume dir ectly.
advanced communications & sensing rev 1 C 25 th july 2011 40 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 8 i nterrupt (nirq) 8.1 introduction the purpose of the nirq pin is to indicate to the h ost (via a falling edge) when any of the events con sidered being time-critical has occurred. non time-critical events can be monitored via i2c by reading regular ly the relevant status bits. 8.2 registers overview 8.2.1 regirqmsk this register allows the host to decide which inter rupt sources he wants to monitor via the nirq signa l. please note that a reset event will always trigger nirq fa lling edge whatever regirqmsk (cf 10) 8.2.2 regirqsrc this register indicates to the host which of the in terrupt sources triggered the nirq signal. more th an one bit can be set if several events occurred before host r eads 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 rea d. 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 th e chip and is used by all interrupt sources to dete ct the relevant events. for each bit, if the relevant block is on i ts 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, pro ximity, etc) - program regirqmsk to start monitoring what is con sidered to be time-critical events - enable the blocks to start regstat update and hen ce nirq process. - each time nirq falling edge occurs, read regirqsr c to know which time-critical event occurred (+ r ead channel data if relevant) - in addition, regstat can be read anytime to get t he whole picture including also what is considered to be non time-critical information.
advanced communications & sensing rev 1 C 25 th july 2011 41 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 9 a uxiliary p ins (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 (proxsensorco n and proxshieldcon) to use an external sensor and/or shield instead of the touchscreens p lates 3. by the host (regaux0-1) to monitor any regstat a nd/or regirqsrc bits in real time without having to use nirq or perform i2c polling.
advanced communications & sensing rev 1 C 25 th july 2011 42 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 10 r eset 10.1 hardware (por and nrst) the chip generates its own power on reset (por) sig nal after a power supply is connected to the vdd pi n. nrst input pin can be used to reset the chip anytim e, it must be connected to vdd (or greater) either directly (if not used), or via a resistor. figure 50 C hardware reset conditions 1. device behavior is undefined until vdd rises abo ve vpor, at which point internal reset procedure is started and nirq is kept low. 2. after t reset , the reset procedure is completed and nirq is rele ased high. 3. in operation, the chip may be reset at anytime b y an external device driving nrst low for t pulse or longer. nirq will go low during the reset phase an d 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 ch ip and all registers to their default values. nirq will go low during the reset phase and chip can be accessed nor mally again after nirq rising edge. additionally bi t 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 t he reset phase and chip can be accessed normally again after nirq rising edge. additionally bit resetstat will be set (cleared when reading regstat). undefined t reset reset signal vdd vpor t pulse 1 2 3 nirq undefined
advanced communications & sensing rev 1 C 25 th july 2011 43 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 11 i2c i nterface 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 i nternal 8-bits registers to set the various paramet ers 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 slav e transmitter/receiver, any register can be written o r read independently of each other. the start and s top commands frame the data-packet and the repeat start condition is allowed if necessary. 2 lines are used to exchange data between an extern al master host and the slave device: scl : s erial cl ock sda : s erial da ta seven bit addressing is used and ten bit addressing is not allowed. any general call address will be i gnored by the chip. the chip is not cbus compatible and can o perate 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 addresse s of the device. on the csp package addr is internall y connected to ground. this is illustrated in table below. package addr address description 0 0x4 8 (100100 0 ) first i2c address qfn 1 0x4 9 (100100 1 ) second i2c address csp 0 0x48 (1001000) first (and unique) i2c address table 9 C 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 sla ve address (sa) is sent, followed by an eighth bit (w=0) ind icating a write. the chip then acknowledges [a] tha t 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 m ore data, a succeeding data byte will follow (wd1), acknowledged by the slave [a]. this sequence will b e repeated until the host terminates the transfer w ith the stop condition [p]. figure 51 C i2c write register the register address increments automatically when successive data bytes (wd1...wdn) are supplied by t he host.
advanced communications & sensing rev 1 C 25 th july 2011 44 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing the correct sampling of the screen by the chip and the host i2c bus traffic are events that might occu r simultaneously. the chip will synchronize these eve nts by the use of clock stretching if that is requi red. 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 b elow. after the start condition [s], the chip slav e address (sa) is sent, followed by an eighth bit (w=0) indicati ng a write. the chip then acknowledges [a] that it is being addressed, and the host responds with a cr byte con sisting in 01 followed by the register address (r a). the chip acknowledges [a] and the host sends the repeat ed start condition [sr]. once again, the chip slave address (sa) is sent, followed by an eighth bit (r=1) ind icating a read. the chip responds with an acknowled ge [a] and the data byte (rd0). if the host needs to read more data it will acknowledge [a] and the chip will sen d the next data byte (rd1). this sequence will be repeated unt il the host terminates the transfer with a nack [n] followed by a stop condition [p]. figure 52 C i2c read register the register address increments automatically when successive data bytes (rd1...rdn) are read by the h ost. the correct sampling of the screen by the chip and the host i2c bus traffic are events that might occu r simultaneously. the chip will synchronize these eve nts by the use of clock stretching if that is requi red. 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 b elow. after the start condition [s], the chip slave address (sa) is sent, followed by an eighth bit (w=0) ind icating a write. the chip then acknowledges [a] tha t it is being addressed, and the host responds with a cr byte con sisting in command(7:0) (see table below). the chip acknowledges [a] and the host sends a stop [p]. figure 53 C i2c write command the sampling of the screen by the chip and the host i2c bus traffic are events that might occur simult aneously. the chip will synchronize these events by the use o f clock stretching if that is required. the stretch ing occurs directly after the last received command bit (see f igure above).
advanced communications & sensing rev 1 C 25 th july 2011 45 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing command command(7:0) function select 1 0 1 0 x chan(2:0) select and bias channel. convert 1 0 1 1 x chan(2:0) convert channel. man 1 1 0 0 x x x x enter manual mode. pendet 1 1 0 1 x x x x enter pen detect mode. pentrg 1 1 1 0 x x x x enter pen trigger mode. table 10 : command codes channel chan(2:0) description x 0 0 0 x channel y 0 0 1 y channel z1 0 1 0 first channel for pressure measurement z2 0 1 1 second channel for pressure measurement rx 1 0 1 x multitouch measurement ry 1 1 0 y multitouch measurement seq 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 be low. after the start condition [s], the chip slave address (sa) is sent, followed by an eighth bit (r=1) ind icating a read. the chip responds with an acknowled ge [a] and the first data byte (rd0). the host sends an acknow ledge [a] and the chip responds with the second dat a byte (rd1). if the host needs to read more channels, it will acknowledge [a] and the chip will send the nex t data bytes. this sequence will be repeated until the hos t terminates with a nack [n] followed immediately b y a stop [p]. the channel data that can be read is defined by reg chanmsk, or the last convert command in manual mode . a maximum number of 12 data bytes can be read when al l channels (x, y, z1, z2, rx, ry) are activated in regchanmsk. the stop [p] (if following the last val id data) releases high the nirq line. all adc relat ed operations (touch conversion, proximity conversion, pen detection) are stopped as long as all valid ch annel data have not been read (ie as long as nirq is low). figure 54 C i2c read channel the sampling of the screen by the chip and the host i2c bus traffic are events that might occur simult aneously. the chip will synchronize these events by the use o f clock stretching if that is required. the stretch ing occurs directly after the address and read bit have been s ent for the i2c read channels command (see figure a bove). the channel data is sent with the following order: x, y, z1, z2, rx, ry. it is coded as described in f igure below typical applications require only x and y coordinat es, thus only 4 bytes of data will be read in this case.
advanced communications & sensing rev 1 C 25 th july 2011 46 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing chan(2:0) rd0 d(11:8) d(7:0) rd1 0 figure 55 C channel data format the 3 bits chan(2:0) are defined in the previous ta ble 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 co nverted. 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 wasnt touched , i.e. pen up (not detected).
advanced communications & sensing rev 1 C 25 th july 2011 47 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 12 r egisters d etailed d escription address name default description 0x00 regtouch0 0x00 0x01 regtouch1 0x20 0x02 regtouch2 0x00 0x03 regtouch3 0x00 0x04 regchanmsk 0xc0 touchscreen interface 0x05 reghapt0 0x00 0x06 reghapt1 0x00 0x07 reghapt2 0x00 0x08 reghapt3 0x80 0x09 reghapt4 0x00 0x0a reghapt5 0x00 haptics interface and temperature sensor 0x0b regprox0 0x00 0x0c regprox1 0x00 0x0d regprox2 0x00 0x0e regprox3 0x00 0x0f regprox4 0x00 0x10 regprox5 0x00 0x11 regprox6 0x00 0x12 regprox7 0x00 0x13 regprox8 0x00 0x14 regprox9 0x00 0x15 regprox10 0x00 0x16 regprox11 0x00 0x17 regprox12 0x00 0x18 regprox13 0x00 0x19 regprox14 0x00 0x1a regprox15 0x00 0x1b regprox16 0x00 0x1c regprox17 0x00 0x1d regprox18 0x00 0x1e regprox19 0x00 0x1f regprox20 0x00 0x20 regprox21 0x01 0x21 regprox22 0x00 proximity sensing interface 0x22 regirqmsk 0x08 0x23 regirqsrc 0x00 0x24 regstat 0x00 interrupt and chip status 0x25 regaux0 0x00 0x26 regaux1 0x00 auxiliary functions 0x3f regreset 0x00 software reset table 12 : registers overview notes: 1) addresses not listed above are reserved and sho uld not be written. 2) reserved bits should be left to their default v alue unless otherwise specified. 3) proximity related registers/bits do not apply t o sx8678.
advanced communications & sensing rev 1 C 25 th july 2011 48 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:4 touchrate 0000 defines the touch coordinates ac quisition 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 values above assume typical foscl, else vary accord ingly. 3:0 powdly 0000 defines the bias settling time for each channels 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 accord ingly. table 13 : regtouch0 (addr 0x00) bits variable default description 7:5 reserved 001 4 tstype 0 defines the type of touchscreen: 0 : 4-wire 1 : 5-wire 3:2 rpndt 00 defines the pen detection circuits pu ll-up resistor value: 00 : 114 kohms 01 : 228 kohms 10 : 57 kohms 11 : 28 kohms 1:0 filt 00 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 va lues (nfilt = 7) table 14 : regtouch1 (addr 0x01)
advanced communications & sensing rev 1 C 25 th july 2011 49 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:4 reserved 0000 3:0 setdly 0000 defines the bias settling time for each channels 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 accord ingly. table 15 : regtouch2 (addr 0x02) bits variable default description 7:6 reserved 00 5:3 rmsely 000 cf. 4.5 2:0 rmselx 000 cf. 4.5 table 16 : regtouch3 (addr 0x03) bits variable default description 7 xconv 1 enables x channel conversion: 0 : off 1 : on 6 yconv 1 enables y channel conversion: 0 : off 1 : on 5 z1conv 0 enables z1 channel conversion: 0 : off 1 : on 4 z2conv 0 enables z2 channel conversion: 0 : off 1 : on 3 reserved 0 2 rxconv 0 enables rx channel conversion: 0 : off 1 : on 1 ryconv 0 enables ry channel conversion: 0 : off 1 : on 0 reserved 0 table 17 : regchanmsk (addr 0x04) bits variable default description 7 haptmode 0 defines the haptics mode/input: 0 : pwm 1 : i2c
advanced communications & sensing rev 1 C 25 th july 2011 50 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 6:5 hapttypeen 00 defines the haptics load: 00 : off. haptics block disabled. 01 : lra 10 : erm 11 : reserved 4 haptrange 0 defines min prescaler value: 0 : 128 1 : 256 3:0 haptgain 0000 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 variable default description 7:6 reserved 00 5:3 haptsquelch 000 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 2 tempwrnirqedg 0 enables tempwrnirq to be generate d when the chip temperature gets below the alarm threshold : 0 : off. tempwrnirq generated only when the chip te mperature gets above the alarm threshold. 1 : on. tempwrnirq generated both when the chip tem perature gets above and below the alarm threshold. 1 tempalrmirqedg 0 enables tempalrmirq to be genera ted when the chip temperature gets below the alarm threshold : 0 : off. tempalrmirq generated only when the chip t emperature gets above the alarm threshold. 1 : on. tempalrmirq generated both when the chip te mperature gets above and below the alarm threshold. 0 tempalwayson 0 enables the temperature monitoring even when no operation (touch, proximity, haptics) is enabled: 0 : off 1 : on table 19 : reghapt1 (addr 0x06)
advanced communications & sensing rev 1 C 25 th july 2011 51 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:0 haptamp 0x00 defines the haptics output polarit y 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 variable default description 7:5 haptbw 100 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) 4 hapthz 0 sets moutp and moutn to high impedance ( hz): 0 : normal 1 : hz 3 haptshortprot 0 disables short-circuit protection : 0 : on . a short-circuit event will automatically s top haptics operation. 1 : off. a short-circuit event will not stop haptic s operation. in both cases haptshortstat is still updated (and h ence an interrupt can still be generated if needed) 2:0 hapttimermsb 000 defines the haptics timer over flow value used to generate the lras 128 or 256 multiple frequency from min. table 21 : reghapt3 (addr 0x08) bits variable default description 7:0 hapttimerlsb 0x00 defines the haptics timer ove rflow value used to generate the lras 128 or 256 multiple frequency from min. hapttimer[9:0] values below 8 (ie 0-7) are reserved . table 22 : reghapt4 (addr 0x09) bits variable default description 7:0 reserved 0x00 table 23 : reghapt5 (addr 0x0a) bits variable default description 7 proxrawfiltsel 0 defines the proximity raw filter ing range for proxrawfilt : 0 : fast 1 : slow 6 proxirqsel 0 defines the function of bits 5 of re girqmsk and regirqsrc. 0 : proxfar 1 : proxconvdone
advanced communications & sensing rev 1 C 25 th july 2011 52 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5:4 proxhyst 00 defines the proximity detection hys teresis : 00 : off 01 : 32 10 : 128 11 : 512 3:0 proxscanperiod 0000 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) bits variable default description 7:0 proxthresh 0x00 defines the proximity detection threshold (for proxstat update). threshold = 16 x register value table 25 : regprox1 (addr 0x0c) bits variable default description 7:6 proxclosedeb 00 defines the close debounce (f or proxstat update): 00 : off 01 : 2 samples 10 : 4 samples 11 : 8 samples 5:4 proxfardeb 00 defines the far debounce (for p roxstat update): 00 : off 01 : 2 samples 10 : 4 samples 11 : 8 samples 3:0 proxcompprd 0000 defines the periodic compensat ion : 0 : off else : register value x 128 samples table 26 : regprox2 (addr 0x0d) bits variable default description 7:0 proxstuck 0x00 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) bits variable default description 7:0 proxavgposthresh 0x00 defines the average positive threshold (for co mpensation). threshold = 8 x register value table 28 : regprox4 (addr 0x0f)
advanced communications & sensing rev 1 C 25 th july 2011 53 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:5 proxavgposdeb 000 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 4:2 proxavgposfilt 000 defines the average positive filter coefficient : 000 : 0 (ie filtering off) 001 : 1 C 1/2 010 : 1 C 1/4 011 : 1 C 1/8 100 : 1 C 1/16 101 : 1 C 1/32 110 : 1 C 1/64 111 : 1 C 1/128 1:0 proxrawfilt 00 defines the raw filter coefficie nt. if proxrawfiltsel = 0 : 00 : 0 (ie filtering off) 01 : 1 C 1/2 10 : 1 C 1/4 11 : 1 C 1/8 if proxrawfiltsel = 1 : 00 : 1 C 1/16 01 : 1 C 1/32 10 : 1 C 1/64 11 : 1 C 1/128 table 29 : regprox5 (addr 0x10) bits variable default description 7:0 proxavgnegthresh 0x00 defines the average negative threshold (for co mpensation). threshold = C 8 x register value table 30 : regprox6 (addr 0x11) bits variable default description 7:5 proxavgnegdeb 000 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 4:2 proxavgnegfilt 000 defines the average negative filter coefficient : 000 : 0 (i.e. filtering off) 001 : 1 C 1/2 010 : 1 C 1/4 011 : 1 C 1/8 100 : 1 C 1/16 101 : 1 C 1/32 110 : 1 C 1/64 111 : 1 C 1/128 1 proxhighim 0 enables high noise immunity mode : 0 : off 1 : on, at the expense of higher power consumption. 0 reserved 0 table 31 : regprox7 (addr 0x12)
advanced communications & sensing rev 1 C 25 th july 2011 54 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:4 reserved 0000 3:0 proxrawmsb 0000 provides the proximity raw info rmation for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 32 : regprox8 (addr 0x13) bits variable default description 7:0 proxrawlsb 0x00 provides the proximity raw info rmation for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 33 : regprox9 (addr 0x14) bits variable default description 7:4 reserved 0000 3:0 proxusefulmsb 0000 provides the proximity infor mation for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 34 : regprox10 (addr 0x15) bits variable default description 7:0 proxusefullsb 0x00 provides the proximity infor mation for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 35 : regprox11 (addr 0x16) bits variable default description 7:4 reserved 0000 3:0 proxavgmsb 0000 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) bits variable default description 7:0 proxavglsb 0x00 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) bits variable default description 7:5 reserved 0000 4:0 proxdiffmsb 0000 provides the proximity differe ntial information for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 38 : regprox14 (addr 0x19) bits variable default description 7:0 proxdifflsb 0x00 provides the proximity differe ntial information for monitoring purposes. signed, 2's complement format. read-only (using proxconvdone), do not write. table 39 : regprox15 (addr 0x1a) bits variable default description 7:0 proxoffsetmsb 0x00 provides the proximity compe nsation offset information for monitoring purposes. read-only (using proxconvdone), do not wr ite. table 40 : regprox16 (addr 0x1b)
advanced communications & sensing rev 1 C 25 th july 2011 55 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:0 proxoffsetlsb 0x00 provides the proximity compe nsation offset information for monitoring purposes. read-only (using proxconvdone), do not wr ite. table 41 : regprox17 (addr 0x1c) bits variable default description 7 reserved 0 6:4 proxsensitivity 000 defines the sensitivity : 000 : 0 (min) 001 : 1 010 : 2 011 : 3 100 : 4 101 : 5 110 : 6 111 : 7 (max) 3:1 proxfreq 000 defines the operating frequency : 010 : 64 khz 011 : 90 khz 100 : 112 khz 101 : 150 khz (recommended) else : reserved 0 reserved 0 table 42 : regprox18 (addr 0x1d) bits variable default description 7:4 proxsensorcon 0000 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 3:0 proxshieldcon 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) bits variable default description 7:6 reserved 00 5:3 proxboost 000 enables proximity boost mode (hig her sensitivity) : 100 : on 110 : off (recommended; compulsory when sensor is t s) else : reserved 2:0 reserved 000 must be set to 100. table 44 : regprox20 (addr 0x1f) bits variable default description 7:0 reserved 0x01 must be set to 0x81. table 45 : regprox21 (addr 0x20) bits variable default description 7:0 reserved 0x00 table 46 : regprox22 (addr 0x21)
advanced communications & sensing rev 1 C 25 th july 2011 56 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7 haptshortirqen 0 enables the haptshort interrupt. 0 : off 1 : on 6 proxcloseirqen 0 enables the proxclose interrupt. 0 : off 1 : on 5 proxfarirqen/ proxconvdoneirqen 0 enables the proxfar/proxconvdone interrupt. cf r egprox0[6] 0 : off 1 : on 4 proxcompdoneirqen 0 enables the proxcompdone inte rrupt. 0 : off 1 : on 3 pentouchirqen/ touchconvdoneirqen 1 enables the pentouch/touchconvdone interrupt 0 : off 1 : on 2 penreleaseirqen 0 enables the penrelease interrup t. 0 : off 1 : on 1 tempwarningirqen 0 enables the tempwarning interr upt. 0 : off 1 : on 0 tempalarmirqen 0 enables the tempalarm interrupt. 0 : off 1 : on table 47 : regirqmsk (addr 0x22) bits variable default description 7 haptshortirq 0 gives the haptshort interrupt sour ce status. (ie haptshortstat rising edge) 6 proxcloseirq 0 gives the proxclose interrupt sour ce status. (ie proxstat rising edge) 5 proxfarirq/ proxconvdoneirq 0 gives the proxfar (ie proxstat falling edge), or proxconvdone (ie convstat falling edge after proxim ity conversion) interrupt status depending on proxirqse l . 4 proxcompdoneirq 0 gives the proxcompdone interrup t source status. (ie proxcompstat falling edge) 3 pentouchirq/ touchconvdoneirq 0 gives the pentouch/touchconvdone interrupt source status. (ie in pendet mode -> penstat rising edge, else -> conv stat falling edge after touch conversion) 2 penreleaseirq 0 gives the penrelease interrupt so urce status. (ie penstat falling edge) 1 tempwarningirq 0 gives the tempwarning interrupt source status. (ie tempwarningstat rising/falling edge depending on tempwrnirqedg) 0 tempalarmirq 0 gives the tempalarm interrupt sour ce status. (ie tempalarmstat rising/falling edge depending on tempalrmirqedg) table 48 : regirqsrc (addr 0x23) bits variable default description 7 haptshortstat 0 gives the haptics short-circuit i nstantaneous status : 0 : no short circuit is currently present 1 : a short circuit is currently present 6 resetstat 0 gives the reset latched status : 0 : no reset occurred 1 : a reset occurred this bit is cleared when regstat is read.
advanced communications & sensing rev 1 C 25 th july 2011 57 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 5 proxstat 0 gives the proximity instantaneous status: 0 : far (or proximity sensing disabled) 1 : close proxstat (and proxavg) is automatically frozen to i ts 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. 4 proxcompstat 0 when read, this bit indicates gives the compensat ion instantaneous status : 0 : no compensation is currently pending 1 : a compensation is currently pending execution a nd/or completion when set to 1, triggers a compensation for next s can period. 3 convstat 0 gives touch/proximity conversion instantaneous st atus : 0 : no touch or proximity conversion is currently r unning 1 : a touch or proximity conversion is currently ru nning 2 penstat 0 gives the pen instantaneous status : 0 : released/up 1 : touching/down 1 tempwarningstat 0 gives the temperature warning instantaneous statu s : 0 : temperature is below warning threshold 1 : temperature is above warning threshold 0 tempalarmstat 0 gives the temperature alarm instantaneous status : 0 : temperature is below alarm threshold 1 : temperature is above alarm threshold table 49 : regstat (addr 0x24) bits variable default description 7 reserved 0 6 aux1digouten 0 enables the digital output capabil ity of aux1 0 : off 1 : on, cf. aux1digout. bit is ignored if tstype = 1 or proxsensorcon = 000 1 5 aux2digouten 0 enables the digital output capabil ity of aux2 0 : off 1 : on, cf. aux2digout. bit is ignored if proxsensorcon = 0010 4 aux3digouten 0 enables the digital output capabil ity of aux3 0 : off 1 : on, cf. aux3digout. bit is ignored if tstype = 1 or proxshieldcon = 001 1 3:0 aux1digout 0000 defines the digital signal to o utput 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)
advanced communications & sensing rev 1 C 25 th july 2011 58 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing bits variable default description 7:4 aux2digout 0000 defines the digital signal to o utput 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) 3:0 aux3digout 0000 defines the digital signal to o utput 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) bits variable default description 7:0 softreset 0x00 writing 0xde will reset the chip and all registers to their default values. table 52 : regreset (addr 0x3f)
advanced communications & sensing rev 1 C 25 th july 2011 59 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 13 a pplication i nformation 13.1 typical application circuit figure 56 C typical application circuit 13.2 external components recommended values symbol description note min typ. max unit cvdd main supply decoupling capacitor - 1 - uf cmvdd motor supply decoupling capacitor - 10 - uf cvreg regulator decoupling capacitor +/- 20%, esr<1 - 100 - nf rpull host interface pull-ups +/- 50% - 10 - k ctb proximity sensor-to-shield capacitance - - <0.7 1.5 nf rxy proximity sensor serial resistor - - <1 1.5 k rmot motor resistance - 7.5 - - cmout motor output capacitor - - 1 - uf table 53 : external components recommended values 13.3 multitouch gestures 13.3.1 pinch/stretch a simple thumb and forefinger pinch movement enab les a user to enlarge objects onscreen (moving fing ers away from each other) or make them smaller (move th em towards each other). this intuitive zooming func tion replaces the standard point-and-click functionality of a mouse and provides far greater accuracy to th e user. figure 57 C pinch/stretch multitouch gestures
advanced communications & sensing rev 1 C 25 th july 2011 60 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 13.3.2 rotate objects are rotated onscreen by making simple clock wise (right) or counterclockwise (left) movements w ith the anchored thumb and forefinger. this multi-touch fun ction enables swift and accurate positioning of obj ects without needing to point and click repeatedly on a rotate left-right function button in order to achie ve the desired effect. figure 58 C rotate multitouch gestures
advanced communications & sensing rev 1 C 25 th july 2011 61 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 14 p ackaging i nformation 14.1 qfn package figure 59 - outline drawing - qfn figure 60 - land pattern - qfn
advanced communications & sensing rev 1 C 25 th july 2011 62 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing 14.2 csp package figure 61 - outline drawing - csp figure 62 - land pattern - csp
advanced communications & sensing rev 1 C 25 th july 2011 63 www.semtech.com sx8677/sx8678 haptics enabled multitouch 4/5- wire resistive touchscreen controller with proximity sen sing contact information ? semtech 2011 all rights reserved. reproduction in whole or in pa rt is prohibited without the prior written consent of th e copyright owner. the information presented in this document does not form part of any quotation or con tract, is believed to be accurate and reliable and may be cha nged without notice. no liability will b e accepted by the publisher for any consequence of its use. publicati on thereof does not convey nor imply any license un der patent or other industrial or intellectual property rights . semtech assumes no responsibility or liability wh atsoever for any failur e or unexpected operation resulting from misuse, ne glect improper installation, repair or improper handling or unusual physical or electrical stress i ncluding, but not limited to, exposure to parameter s beyond the specified maximum ratings or operation outside the specified range. semtech products are not designed, intended, author ized or warranted to be suitable for use in life- support applications, devices or systems or other c ritical applications. inclusion of semtech products in such applications is un derstood to be undertaken solely at the customers own risk. sh ould a customer purchase or use semtech products for any such unauthorized application, the customer shall indemnify and hold semtech and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs dam ages and attorney fees which could arise. notice: all referenced brands, product names, servi ce names and trademarks are the property of their respective owners. semtech corporation advanced communications and sensing products divisi on 200 flynn road, camarillo, ca 93012 phone: (805) 498-2111 fax: (805) 498-3804

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