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| freescale semiconductor data sheet: product preview document number: CRTOUCHds rev. 3, 04/2013 ? freescale semiconductor, inc., 2007-2012. all rights reserved. this document contains information on a prod uct under development. freescale reserves the right to change or discontinue this product without notice. CRTOUCH the CRTOUCH is a ready play solution devi ce designed to serve as a four wire and five wire resistive touch driver and a capacitive touch sensing device in a single 32-pin qfn package. it provi des all the signal interfaci ng and processing to calcul ate x and y coordinates as well as to detect and process two t ouch gestures for human-machine in terface applications. it?s key features are: features ? x and y coordinates calculated from a resistive touc h screen with built-in filter to improve stability ? slide gesture detection for single touch. ? two touch gesture detection for resistive four wire screens ? zoom in and zoom out ? rotate with clockwise and counter clockwise indication. ? four capacitive keys in different configurations ? rotary ? slider ?keypad ? uart communication and i2 c communication available ? baud-rate auto detection pin to enable automatic synchronization with any uart baud-rate between 9600 and 115200 bps using the same uart rx pin ? configurable scanning period that can calculate up to 200 coordinate points per second ? 1.8 to 3.6 volts operation ? 32-pin qfn package ? ?40 c to 105 c operating temperature ? normal run mode, sleep mode, and shutdown mode for lower power consumption operation CRTOUCH data sheet capacitive and resistive touch sensing application specific ic.
CRTOUCH data sheet, rev. 3 freescale semiconductor 2 table of contents 1 pins and connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 1.1 device block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .3 1.2 device pin out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 1.3 recommended system connections . . . . . . . . . . . . . . . .5 1.4 signals description . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 2.1 CRTOUCH resistive touchscreen scanning . . . . . . . . . . . .7 2.1.1 touchscreen electric al signals . . . . . . . . . . . . . . .7 2.1.2 CRTOUCH scanning process . . . . . . . . . . . . . . . . .8 2.1.3 resistive events. . . . . . . . . . . . . . . . . . . . . . . . .10 2.1.4 calibration process . . . . . . . . . . . . . . . . . . . . . .10 2.1.5 data fifo . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 2.1.6 resistive gestures . . . . . . . . . . . . . . . . . . . . . . .15 2.2 capacitive subsystem . . . . . . . . . . . . . . . . . . . . . . . . . .17 2.2.1 capacitive touch detection. . . . . . . . . . . . . . . . .17 2.2.2 keypad control . . . . . . . . . . . . . . . . . . . . . . . . . .18 2.2.3 rotary and slider control . . . . . . . . . . . . . . . . . .18 2.3 modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 2.3.1 run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 2.3.2 sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 2.3.3 shutdown mode. . . . . . . . . . . . . . . . . . . . . . . . .20 2.4 internal voltage regulator . . . . . . . . . . . . . . . . . . . . . . .21 2.4.1 internal voltage regulator features . . . . . . . . . . .21 2.4.2 internal voltage regulator modes of operation . .21 3 serial communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.1 i2c interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.1.1 i2c bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.2 i2c start and stop conditions. . . . . . . . . . . 23 3.1.3 i2c transferring data. . . . . . . . . . . . . . . . . . . . . 24 3.1.4 i2c acknowledge . . . . . . . . . . . . . . . . . . . . . . . 24 3.1.5 CRTOUCH i2c slave address . . . . . . . . . . . . . . . 24 3.1.6 message format for writing CRTOUCH . . . . . . . 25 3.2 uart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.1 uart baudrate auto detection. . . . . . . . . . . . . 25 3.2.2 uart communication protocol. . . . . . . . . . . . . 26 3.2.3 registers read through uart. . . . . . . . . . . . . 26 3.2.4 registers write through uart . . . . . . . . . . . . . 27 4 memory map and registers description . . . . . . . . . . . . . . . . 28 4.1 device memory map . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.2 registers description . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4.2.1 resistive touch status registers . . . . . . . . . . . 34 4.2.2 capacitive touch sensi ng status registers . . . 41 4.2.3 resistive touch configuration registers . . . . . . 44 4.2.4 calibration values registers . . . . . . . . . . . . . . . 50 4.2.5 tss configuration registers . . . . . . . . . . . . . . . 51 appendix aelectrical specifications. . . . . . . . . . . . . . . . . . . . . . . 59 appendix bpacking information. . . . . . . . . . . . . . . . . . . . . . . . . . 62 pins and connections CRTOUCH data sheet, rev. 3 freescale semiconductor 3 1 pins and connections 1.1 device block diagram figure 1. block diagram CRTOUCH data sheet, rev. 3 pins and connections freescale semiconductor 4 1.2 device pin out figure 2. device pinout pins and connections CRTOUCH data sheet, rev. 3 freescale semiconductor 5 1.3 recommended system connections figure 3. recommended system connections note 1. resistive touch screen signals are bi-directional only for fo ur-wire screens. for five-wir e 5ws is input and the other four signals are outputs. 2. commsel is connected to ground only if uart communication is desired. otherwise it can be left unconnected. 3. i2c and uart communications are mutually exclusive. only one can work during the device run time. the other pins from the other communication protocol can be un-connected. 4. all unused pins can be left as not connected. connecting them to ground may increase power consumption. CRTOUCH data sheet, rev. 3 pins and connections freescale semiconductor 6 1.4 signals description table 1. signal descriptions pin function used for CRTOUCH description 1 yr y voltage reference 2 touchpending indicates that there is a previous touch event (resistive or capacitive) fwhere data registers have not been read 3 5wur 5-wire upper right connection 4 y+ / 5wlr 4-wire y+ or 5-wire lower right connection 5 x+ / 5ws 4-wire x+ or 5-wire sense connection 6 y? / 5wul 4-wire y? or 5-wire upper left connection 7vdda v dd signal for the adc 8 vssa v ss signal for the adc 9-11 nc no connect 12 vreg_in voltage regulator input 13 v33_out voltage regulator output ?3.3 volts 14 vss v ss ? connect to digital ground 15 x? / 5wll 4-wire x? or 5-wire lower left connection 16 electrode1 capacitive touch sensing key #1 17 xr x voltage reference 18 electrode2 capacitive touch sensing key #2 19 electrode3 capacitive touch sensing key #3 20 electrode4 capacitive touch sensing key #4 21 nc no connect 22 baudrate auto detect signal used to enable baud rate auto detection 23 i2caddrsel i2c address selection pin is used as bit 1 of the i2c address 24 vdd v dd ? connect to system regulated power supply 25 vss v ss ? connect to digital ground 26 i2c1_sda i2c ? bidirectional sda communication signal 27 i2c1_scl i2c ? clock signal. must be driven by the bus master 28 reset reset signal 29 com select communication select pin. 0 = uart. 1 = i2c 30 wakeup signal used to wake the CRTOUCH when configured to go into sleep or shutdown modes. while in sleep mode, this pin should be held down with a logical 0 to communicate with the device. 31 uart_rx uart reception pin 32 uart_tx uart transmission pin functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 7 2 functional description the capacitive and resistive touch (CRTOUCH) is a device capable of interfacing with 4-wire and 5-wire resistive touch screens. it is capable of detecting single touch slide and two-touch ro tate and pinch gestures. CRTOUCH includes a calibration procedure to increase the touch detection accuracy and configurable low power and shutdown modes to reduce power consumption. 2.1 CRTOUCH resistive touchscreen scanning 2.1.1 touchscreen electrical signals the types of resistive touchscreen supported by this device are pa ssive elements composed of two layers of conductive material uniformly distributed across the screen . due to the resistivity of the conductive material, it can be seen as a resistor betw een the terminals of each layer. the following figure shows the constr uction of the 4 and 5 wire type s of screens, and their simpli fied electrical equivalent circuit. figure 4. construction and electrical e quivalent of a four wire touchscreen figure 5. construction and electrical e quivalent of a five wire touchscreen CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 8 when a voltage is applied at the terminal s of one layer, the voltage is linearly distributed across the conductive material. fo r a four wire screen, the coordinates of the point of contact can be determined by applying voltage to one layer and reading the voltage on the other. for a five wire screen, one layer is us ed only for reading the voltage, while the other has voltages appl ied in different combinations for determining the value of each axis. the following table shows how the signals are activated for x and y measurements in each type of screen. considering these scanning sequences, the sc reen?s origin (coordinate 0,0) is located in the intersection of the x? and y? terminals for a four wires screen, and at the ll terminal for a fi ve wire screen. it is also important to consider that the co nnection between the conductive material of the screen and the te rminals of the CRTOUCH controller re present a series resistance with th e screen. because of this, the coordinates obtai ned at the edges of the active region of the screen may be a number of counts abo ve 0 and a number of counts below the maximum value. this vari ation is given by the construction of the touchscreen, the impedance of its connection lines, th e size of the active area, and so on. another electrical phenomenon that needs to be considered is the capacitances created in the screen. because the active area is composed of two plates of conductive mate rial, this creates a set of capacitances be tween the two layers. when combined with the resistors created in the screen, these fo rm an rc circuit with an a ssociated stabilization time constant. if the voltage of one layer is read before it stabilizes, then a deviation from the real coordinate is produced. in some devices esd diodes may be connected to the resistive panel for improve d electrostatic immunity. in this case, lo w capacitance esd diodes must be used to avoid increasing the resulting capacitance. 2.1.2 CRTOUCH scanning process the CRTOUCH has three scanning modes for th e resistive screen. one is active when only x and y coordinate values are desired, the second activates when the pressure meas urement is enabled, and the last one when any of the two touch gestures are enabled. before each sample is taken, the CRTOUCH waits for a configurab le amount of time fo r the signals to stab ilize. the following figure shows the differences in the scan ning process for each scanning mode. table 2. signal states for a four wire screen measurement x+ x? y+ y- xv dd v ss zz yz z v dd v ss table 3. signal states for a five wire screen measurement ur ul lr ll xv dd v ss v dd v ss yv dd v dd v ss v ss functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 9 figure 6. scanning process for x, y, pressure, and two touch gestures as seen in the previous figure, the scanning sequence repeats at a fixed period of time. this period is configurable in the sampling time register and may be in the range of 5 ms to 100 ms. the CRTOUCH scans the screen signals only when a touch is detected. when the screen is not touched, the devi ce stays in a standby state. at the end of the scanning process, a set of coordinates is pr oduced. these coordinates have a default resolution of 12 bits, o r 4096 points per axis. however, this resolu tion may be modified to reflect the propor tions of the screen more accurately (typica l screens have a 4:3 or 16:9 proportion). this can be done by writing to the horizontal resolution and vertical resolution, which correspond to the x and y resolution respectively. the resulting x and y values are scaled to fit into this resolution. the CRTOUCH is capable of autodetecting the type of the screen connected. the type of screen detected is reflected in the statu s register 2. only two touch gestures and pressure detection is available for 4 wire screens, a nd cannot be enabled when a 5 wire screen is connected. x stabilization y stabilization x y sampling period x x stabilization y stabilization x y1 sampling period y2 z1 z2 x z stabilization x stabilization y stabilization x y1 sampling period y2 z1 z2 xr yr x z stabilization x stabilization y stabilization scanning process for x and y coordinates only scanning process for x ,y, and pressure CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 10 2.1.3 resistive events the CRTOUCH has a touchpending signal that can assert on configur able events in the system to alert the host of a new event that requires attention. this signal can be used by the host to avoid time based polling of the status of the device and theref ore unnecessary use of the communication bus. when ever an event is detected in the system, it will be reflected in its associated b it in status register 1. all event bits of this register remain latched and are cleared until the re gister is read. this avoids lo sing any detected event if the host cannot read the status of the device for several samplin g periods. each event can also be enable d to assert the touchpending signal through the triggers enable re gister. by setting the bits in this register, when an event is recorded in the status register the touchpending signal is asserted, and remains asserted until the status is read. the most basic events that are related to the touchscreen are the resistive new samp le and the touchscreen release events. the resistive new sample is triggererd when a new sample of the sc reen coordinates is available, which means that it is produced at the touch detection and subsequently at every scan period. the re lease event is produced only when the screen transitions from touched to not touched. in this case the last valid coordinates value remains in the coordinate registers. additional to the events status, the status register 1 reflects the state of the scr een through its most significant bits, scre en touched and two touch bits. these bits are updated with each sa mpling period and unlike the even ts bits, they are not latched and are not cleared with a register read, so their value always reflects the state of the screen at the last scanning sequence . when the screen transitions to the touched state, the resistive touch screen to uched and the resistive new sample event bits in the resistive touch status register 1 are set. with every new coordinate sample, the resistive touch screen touched and the resistive new sample event bits will be set after the coordi nate values are available in the x and y coordinates registers. when the screen is released, the resistive new sample event bit will be set, indicating the end of the scanning sequence, but the resistive touch screen touched bit will now be cleared, reflecting the released st ate of the screen. af ter this condition i s met, no more touchscreen events will be repo rted in the status register or the touchpending pin until a new touch is detected i n the screen. the touchpending signal is active lo w and is capable of driving an led if user feedback is desired. 2.1.4 calibration process the resistive touch screen should be calibrated to get an accura te performance. this inlcudes x and y coordinate and gesture detection. the calibration process consists of a series of points touched by the user to give the device references on the scre en orientation, offsets, and linearity. two di fferent processes may be executed: one, for only single touch calibration, the other for single and two touch calibration. in both cases, three different points need to be touched for single touch calibration. it is recommended that these points be touched with a stylus to increa se the precision achieved. in the case of two touch calibration , two pairs of points need to be touched. as expected the two touch gestures are performed with fingers, these pairs of points must also be pressed with fingers. the three single touch calibration points are the following: the fi rst coordinate should be at 10% of x and 10% of y axis. the second coordinate should be at 50% of x and 90% of y axis. th e third coordinate should be at 90% of x and 50% of y axis. the two pairs of two touch coordinates are the following and may be pressed in any order: the firs t pair is at 50% on the x axi s and 10% and 90% on y axis; the second pair is 50% on y axis and 10% and 90% on x axis. these percentages correspond to the graphic display screen reso lution. the horizontal display resolution and vertical display resolution must be configured with the corresponding display re solution before executing the calibration process. note that both registers must be written for their new values to take ef fect. when the CRTOUCH is calibra ted with the correct resolution, the x and y coordinates calculated by the devi ce directly correspond to the display pi xels and need no additional processing by the graphics controller. usually the user application displays an image showing the calibration points one at a time that must be touched to calibrate the screen. for increased precision, the CRTOUCH performs a validation of the touched points during calibration to determine if the values are within the expected range. when the validation is not positive, a calibration error is signaled in the status error registe r. this validation mechanism does not prevent the device from being calib rated. it serves as informat ion to the host processor to determine if the calibration was executed co rrectly. other methods of validation can be to display an additional point in the display and verify that the coordinate reported by the CRTOUCH corresponds to the displayed point. the built-in validation mechanism is accurate only with in a 5 diphase between the display and the touch panels. functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 11 figure 7. touch points for single touch calibration figure 8. touch pairs for two touch calibration the calibration process is initiated by setting bit6 into the tr igger events register. for two t ouch calibration at least one o f the two touch gestures must be enabled prior to starting the calibra tion process. it is also important to properly configure the resolution values to match the screen ratio , to increase the precision of the gestures detection especially for the rotate gest ure. the following diagrams show the sequence of actions followed after setting the calibration bit to start the process. CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 12 figure 9. single touch calibration sequence functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 13 figure 10. single and two touch calibration sequence CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 14 during calibration, the touch screen scan period is fixed at 10 ms, regardless of the value configured in the sampling rate register. for each point, 128 samples ar e taken, so each point should be held at least for 1.3 s for proper calibration. the calibration processed may be stopped at anytime by clearing bit6 on the trigger events register. asampling period must pass before enabling it again for a new calibration process. to discard an established calibration both of the display resoluti on registers must be written. it is also possible to calibrate the CRTOUCH device through the calibration values set of registers without any touches required by the user. this is particularly useful for factory calibration to reduce the time required for t his process. in this case, a system must be manually calibrated to generate the calibration values that can be reproduced to other devices. it is important to consider that the precision achieved by this method depends on the repeatability of the touch senso r impedances by the manufacturer. after writing the values to these registers the CRTOUCH must be reset for the calibration to ta ke effect. 2.1.5 data fifo the device has three fifo buffers, one for x coordinates, one for y coordinates, and on e for pressure values. each fifo buffer stores up to16 samples and new samples can not be stored once th e fifo buffer is full. each point touched on the screen yields one x coordinate and one y coordinate which are store onto its respective fifo buffer. if pressu re is enabled on the device, then each point yields also a pressure value th at is stored onto its respective fifo buffer. the three fifo buffers are sync hronized and should be read in sequence. the device has a m echanism avoiding that just one fifo buffer is read. if there are samples on the fifo buffers and just one of them is read several times the device will report the same value until the other fifo buffers is read. this mean s if the pressure is enabled the x fifo buffer, y fifo buffer, and pressure fifo buffer should be read once before trying to read any of them again. if pressure is disabled then only x fifo buffer and y fifo buffer should be read. setting the rtfifoen bit into the fifo setup register enables th e fifo buffers. clearing this bi t disables the fifo buffers. x, y, and pressure fifo buffers are flushed each time the fifo setup register is written. the device returns the value 0xffff if the fifo buffers are disabled or empty. if the fifo buffers are enabled a watermark can be configured to generate an event once the number of samples stored onto the fifo buffers are bigger or equal than the watermar k. the watermark is disabled by setting a zero value. figure 11. fifo watermark example functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 15 2.1.6 resistive gestures the CRTOUCH controller has built-in gestures detection cap abilities with unique support for zoom and rotate multi-touch gestures, as well as single touch slides. this feature offloads the host processor of continuous coordinate reading and process ing for gesture detection. 2.1.6.1 slide a slide is detected for linear motion in an y region of the screen in a direction parall el to any axis of the screen. this mean s that any motion that varies only one axis can be detected as a slide. the de tection algorithm supports a deviation of 7.5 from the axis direction to still consider the mo tion as a slide. the following figure sh ows the valid ranges for a slide motion. figure 12. slide valid regions the slide gesture is enabled through the slide enable bit in the configuration register, and it is reported through the slide e vent bit in the status register 1. a slide can be performed in four different directions: horizontal or vertical, positive or negati ve in each case. the direction of the ge sture is reported in the status register 2 th rough the slide directi on [1:0] bits. the follow ing table shows the reported value for each case. the slide gesture is reported when the motion distance is higher than a configurable threshold. this threshold is a portion of the screen resolution across each axis. for a vert ical slide, a portion of the y resolution is the threshold and for a horizontal s lide, a portion of the x resolution is the threshold. this portion is defined by the slide steps register value. for a value of ten, the table 4. slide gesture directions motion direction slide direction [1:0] x0 < x1, y0 = y1 horizontal positive 00 x0 > x1, y0 = y1 horizontal negative 01 y0 < y1, x0 = x1 vertical positive 10 y0 > y1, x0 = x1 vertical negative 11 CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 16 threshold is set to one tenth of the resolution; a value of one would mean one unit of the resolution, which cannot produce a slide because no motion may have a di stance greater than the resolution. the slide displacement register reports the accumulated steps of the motion afte r it begins, therefore each time the threshold is crossed, this value is incremente d. this value is reset if a change of direction is detected or when th e screen is touched afte r a release. 2.1.6.2 two touch gestures the CRTOUCH device is capable of detecting when two independent touches are present in the scr een and when zoom and rotate gestures are performed by these two touches. two touch detection is enabled when eith er zoom or rotate are enabled in the configuration register. when two touches are detected, the two touch bit in the status re gister 1 is set. in this state, coordi nates reported in the x and y registers should be disregarded by th e display controller. when det ecting a two touch event, the CRTOUCH continuously measures displacemen t of the fingers. this displacement may re flect in terms of the distance between the fingers (zoom gesture), the sl ope of the line between the fingers (rotate gesture), or both. for two touch gestures to operate, it is mandatory to run the calibration process described in section section 2.1.4, ?calibration process .? two touch gestures and display resolution must be config ured before running the calibra tion to properly calibrate the gesture detection. for two touch gestures, the CRTOUCH uses in ternally a different resolution for the distances between the fingers in each axis. the smaller axis has a fixed resolution of 1000, while the other axis resolution is calculated to match t he screen proportions. for a screen with 16:9 proportions, for exam ple, one axis would have a resolution of 1000 and the other of 1777. the screen proportion is calculated acco rding to the vertical resolution and ho rizontal resolution values. these values are used to calculate the distance between the fingers. eqn. 1 eqn. 2 or eqn. 3 whichever is the highest. eqn. 4 the signals required for two touch detection are obtained through the resistors connected to the xr and yr signal. unexpected behaviors may be produced if these resistors are not connected and two touch gestures are enabled. 2.1.6.3 zoom gesture when the distance between the fingers vari es, a zoom gesture is detected. if the distance increases, a zoom-in direction is reported through the rtszd bit in the status register 2. if the distance decreas es, a zoom-out direction is reported through th e rtszd bit in the status register 2. in eith er case, the rtsz bit is set in status re gister 1. similar to the slide gesture, th e zoom gesture is reported when a threshold is crossed. this threshold is approximately one tenth of the smaller axis of the screen. t he zoom size register is updated each time the threshold is crossed and is cumulative th roughout the gesture. the value of this register is equal to one tent h of the distance displacement. eqn. 5 twotouchresolutiona 1000 = twotouchresolutionb 1000 horizontalresolution verticalresolution --------------------------------------------------------- - ? = twotouchresolutionb 1000 verticalresolution horizontalresolution --------------------------------------------------------- - ? = maxtwotouchdis ce tan resolutiona ? 2 resolutionb ?? 2 + = zoomsize initdis ce tan actualdis ce tan ? 10 ---------------------------------------------------------------------------------- - = functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 17 the maximum distance reported in the zoom size register can vary this depends on the proportions of the screen. 2.1.6.4 rotate gesture the rotate gesture is reported when a variation of the slope betw een the fingers is detected. this variation must be at least 10 for it to be reported in the rtsr of the status register 1. the direction of the rotate gesture is reported in the rtsrd in the status register 2. the rotate angle regist er reflects the cumulative angl e that has been displaced in that direction. this ang le is reported in radians with 5 fractional b its and 3 integer bits. this determines a limit of 456 of continuous rotation that c an be reported by the CRTOUCH. the following equation can be used to convert the value of the rotate angle register to a value in degrees. eqn. 6 2.2 capacitive subsystem the CRTOUCH controller supports up to four capacitive electrodes as an extended interface. these electrodes may be detected independently or they can be arranged in a keypad, rotary or slider control configuration. th e capacitive subsystem is enabled through the configuration regist er with the capacitive control [1:0] bits according to ta ble 4. additionally, each of the electrodes of the CRTOUCH controller may be individually enabled or disabled in the electrode enablers register. when enabled, the capacitive electrodes ar e scanned sequentially, from e0 to e3, at a fixed rate of 7 ms. the capacitive subsystem of the CRTOUCH controller has a set of configur ation and status registers to control several features. note before the desired control is enabled through the configuration register, the desired events to be detected must be enabled in the capaciti ve register; otherwise the control will not be enabled. 2.2.1 capacitive touch detection the touch detection is based on a baseline tracking algorithm and thresholds for touch detection. when the system is enabled, an initial baseline is calculate d and continuous baseline recal ibration can be enable d through the dctracker feature with the dc tracker enable bit in the capacitive system config uration. this recalibration is executed at a fixed number of scanning periods, determined by the dc tracker rate register value. sin ce the scanning period is fixed at 7 ms, the recalibration period is equal to the dc tracker rate register value multiplied by 7 ms. to detect a touch, the capacitance samp les taken for each electrode are compared against the baseli ne. if a number of consecutive samples exceed a certain threshold then that electrode is considered and re ported as touched. these thresholds are defined by the ex sensitivity registers and represent the minimu m difference that must exist be tween a capacitive sample and table 5. capacitive control configuration bits capacitive control [1:0] configuration 00 capacitive subsystem disabled 01 rotary control enabled 10 slider control enabled 11 keypad control enabled ? rotateangle ?? ? 180 32 ? ------------------------------------------------- - = CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 18 the signal baseline for a touch to be detected. to avoid false touch detection due to sporadic noise, the response time registe r defines how many samples the algorithm will consider to determine a touch or a no touch condition. after an electrode has been detected as touched, recalibration is no t performed for that electrode to avoid recalibrating the baseline at a non-idle signal level. however, under certain envi ronmental conditions, large and sudden changes in the measured capacitance may occur which may trigger a touch detection. if this condition persists (excessive humidity over an electrode, fo r example), the affected elect rode will not be able to detect real touches. for this kind of scenario, the stuck key feature allo ws the host to define a touch timeout,after which the touche d status is released and the electrode is recalibrated. the actual status of each individual electrode may be read at the electrode status regi ster. each bit represents the status of one electrode, reporting a 1 when the elect rode is detected as touched and a 0 when the electrode is not touched. for application customization of these para meters, the CRTOUCH controller provides a set of registers that allow the analysis o f the capacitance behavior of each electrode under the specific ap plication conditions. the electrode baseline registers and electrode instant delta regist ers provide this information. the resolution of the capacitive samples an d the calculated baselines can be modi fied through the capacitive resolution registers. increasing or decreasing the reso lution is useful depending on the thickness of the dielectric used. this allows to modify the signal (touch) to noise ratio for more flexibility on the touch detection. this value is only effective after a rese t, a reset is then needed to make a change in this register to take effect. 2.2.2 keypad control the keypad control supports the reporting of touch or release even ts for each individual electrode. these events are reported through an events buffer and each of them is enabled through the events register. the events buffer is mapped to the electrodes fifo register of the device. each read of this register returns the oldest previously stored in the buffer, until the buffer is empty and any subsequent read returns a value of 0xff. the format of the events in the bu ffer may be consulted in the registers sect ion of this document. additionally to the touch detection, the keypad control provides an autorepeat feature, to log new touch events into the buffer at a certain rate after detecting the electr ode as touched for a period of time. the auto-repeat start regi ster controls the ti meout before it starts logging new events, and th e auto-repeat rate register controls how of ten a new event is stored in the buffer. the keypad control also provides the capabilit y of restricting the number of keys that may be pressed at the same time. this is done by writing a value different than 0 in the max touches regist er. when the number of simultan eous touches is equal to the max touches register, no new touch events for additional keys are st ored in the events buffer unti l one or more keys are releas ed. 2.2.3 rotary and slider control the slider and rotary control types provide support for linear or circular arrangements of electro des. a rotary may be seen as a circular slider, where the first and last electrodes are adjacent. in th e case of a rotary a simultan eous touch of these two el ectrodes is considered valid, where in a slider it is not. this is th e only difference between these two types of controls, otherwise al l of their behavior is the same. slider and rotary controls are oriented to the detection of motion through the control, so they provide the capability to detec t this motion, report its direction, and the amount of displ acement. the control is also capable of reporting when the initial to uch is detected, when the motion en ds and when all of the control?s electrodes have been released. all these events are enabled through the events register. two status registers are provided for these controls, the static status register and the dynamic status register. the dynamic status register reports if movement is be ing detected at the moment through the movement flag, reports the direction of this movement in the direction bit and how many positions were advan ced since the last status. the st atic status reports if the cont rol is currently touched through the touch flag, the position of the touch, and if an invalid position is detected. to increase the number of positions detectab le in a rotary or slider control, positio ns ?between? the electrodes are also repor ted. this means that when two electrodes are to uched, the control reports a position differ ent than the position of each of the touc hed functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 19 electrodes. for example, e0 corresponds to position 0, e0 and e1 correspond to position 1, and e1 corresponds to position 2. when more than two electrodes are touche d, the central position is reported. 2.3 modes of operation the CRTOUCH operating modes are described in this section. entry in to each mode and exit from each mode as well as the function while in each of the modes are described. 2.3.1 run mode this is the normal operating mode for CRTOUCH which is the de fault mode for a new device. in this mode the device is not entering into low-power nor shutdown modes at any time. serial communications are active all the time waiting for a command to be received. scanning of a resistive to uchscreen panel will be performed periodica lly as defined in the sampling rate regist er. during run mode, all the internal circuitr y remains enabled all the time. all the functions do not have any constraints or spec ial considerations to be used while in this mode. power consumption is higher than in any other operating mode. 2.3.2 sleep mode sleep mode is enabled through the sleepen bit in the configuration register. this mode sends the part into a low power mode between scanning periods of a resistive touchscreen panel. when the part is in sleep mode it turn s off the internal clocks for the serial communication peripherals, both uart and i2c. the overall function of the device is the same compared to normal run mode, with the ex ception of commun ication interfaces. 2.3.2.1 CRTOUCH function in sleep mode when sleep mode is enabled, the part will remain in this state until the timeout configured in the sampling rate register expir es. after the sampling rate period expires, the part will start the sequence to scan if the resistiv e touch screen connected has a new coordinate and calculate the x and y coordinates and gestures detection if needed. besides a sampling rate period expiration, there are two addi tional ways to transition from sleep mode into run mode: ? wakeup pin?the active low wakeup pin will transition the part from sleep mode into run mode. while being asserted, the device will remain in run mode. the part will return into sleep mode after the signal has been de-asserted, unless there is an active communi cation (uart or i2c) or the part is actively scanning a resistive touchscreen panel. for the communication case, the commun ication timeout rules will apply before going back to sleep mode. when the part is scanning the resistive touchscreen panel, it will go back to sleep mode as soon as the scanning process finishes. ? serial communication?either uart or i2c can transiti on the part from sleep mode into run mode. each communication interface has speci fic characteristics and rules while working in sleep mode. 2.3.2.2 i2c communication in sleep mode if i2c communication is selected for CRTOUCH communication, a start condition followed by a slave address match can be used to wakeup the part from sleep mode and transition to normal run mode. because the i2c internal clock was turned off until the slave address matched, CRTOUCH answers with a not acknowledge to this initial request. there are two alternatives to use i2c communication with sleep mode enabled: ? include in the host the logic a re-send of the slave addres s with the appropriate read or write request upon reception of a not acknowledge. CRTOUCH data sheet, rev. 3 functional description freescale semiconductor 20 figure 13. CRTOUCH wakeup using i2c communication ? use the wakeup signal to bring the part into normal run mo de before starting any i2c communication. it is important to return the wakeup signal into its idle state (high) after the communication is finished, otherwise the part will remain into normal run mode increasing the overall system power consumption. when the wakeup pin is used to return the part to run mode, the system will remain in this state for 50 ? s. if a new communication starts with a start condition followed by the device slave address and a valid command for the CRTOUCH while in normal run mode, the part will remain in run state. it will return to sleep mode only after the communication remains idle f or 1ms after receiving a stop condition. when the part wakes by receiving its slave address through i2c, it remains in run mode for 1ms waiting for a new communication to start. it goes back to sleep mode after 1 ms of inactivity on the i2c bus. 2.3.2.3 uart communication in sleep mode when uart communication is used for crtouc h, a start bit will transition the part from sleep mode to run mode. when the part is in sleep mode the internal clock used for the uart co mmunication is off. up on reception of a start bit the internal clo ck is re-started, the part returns into normal run m ode and the communication can be resumed normally. in the majority of the cases the byte that wokeup the part is properly received and stored. the exceptio n to this rule occurs w hen the internal circuitry is transitioning from normal run mode (either because of a previous communication, wake up pin use, or screen x and y coordinates calculation) into sleep mode. if the uart start bit is r eceived at the exact moment the internal circuitry starts the transition, the initial byte (start of frame) will be lost. th is will result in a complete frame loss when it occurs. there are three alternatives when enabling sleep mode using uart: ? send the start of frame byte twice in each frame. ? asserting the wakeup pin for at least 10 ? s before sending the start of frame. it is important to return the wakeup signal into its idle state (high) after the communication is finished, otherwise the part will remain in normal run mode increasing the overall sy stem power consumption. ? implementing a timeout on the host side to retry the comman d if there is no response rece ived within the next 1ms of sending the command. 2.3.3 shutdown mode shutdown is enabled through the shutdown bit in the configuration register. this mode sends the part into the lowest power consumption state. in this mode, all the resistive touchscreen scanning , serial communication and any other internal activity a re stopped. this mode is intended for when a device is in a standby or hibernating state and wish es to reduce power consumption to its minimum. there are three ways to co me out of shutdown mode: ? asserting the wakeup signal for more than 10 ? s ? using the reset pin ? optionally enabling a capacitive electrode as wakeup source and performing a touch on it. in all cases the part will recover the latest value for the configuration regi sters and will resume will resume normal operatin g mode. the part will use either normal ru n mode or sleep mode based on the latest configuration for the sleepen bit before going into shutdown. functional description CRTOUCH data sheet, rev. 3 freescale semiconductor 21 any of the capacitive electrodes may be en abled as a low power electrode and can be configured for a scanning period and sensitivity. to enable this electrode as a wakeup source from shutdown, the clpen bit must be enabled in the capacitive system configuration register. enabling this bit inhibits nor mal functioning of all the electr odes, therefore it should only be enabled prior to sending the device into shutdown mode. baseline tracking is not performed for the low power electrode. 2.4 internal voltage regulator the voltage regulator module is a ldo linear voltage regulator to provide 3.3 v power from an input power supply varying from 2.7 v to 5.5 v. it consists of one 3.3 v power channel. th e internal voltage regulator can be used to be the main power supply of the device. when the input power supply is below 3.6 v, the regulator goes to pass-through mode. 2.4.1 internal voltage regulator features ? low drop-out linear voltage regulator with one power channel (3.3 v) ? low drop-out voltage? 300 mv. ? output current?120 ma. ? three different power modes? run, sleep, and shutdown. ? low quiescent curr ent in run mode. ? typical value is around 120 ? a (one thousand times smaller than the maximum ? load current). ? very low quiescent current in standby mode. ? typical value is around 1 ? a. ? automatic current limiting if the load current is greater than 290 ma. ? automatic power-up once some voltage is applied to the regulator input. ? pass-through mode for regulator input voltages less than 3.6 v ? small output capacitor? 2.2 ? f ? stable with aluminum, tant alum, or ceramic capacitors. 2.4.2 internal voltage regu lator modes of operation the regulator has these power modes: ? run? the regulating loop of the run regulator and the sleep regulator are active, but the switch connecting the sleep regulator output to the external pin is open. ? sleep? the regulating loop of the ru n regulator is disabled and the st andby regulator is active. the switch connecting the sleep regulator output to the external pin is closed. ? shutdown? the module is disabled. this is the recommended connections to power CRTOUCH from internal voltage regulator: CRTOUCH data sheet, rev. 3 serial communications freescale semiconductor 22 figure 14. connections to power CRTOUCH from internal voltage regulator figure 15. recommended connections to power external circuitry from internal voltage regulator 3 serial communications the CRTOUCH is a four wire and five wire resistive touch scr een and a four key capacitive touch sensing device. it can interact with a master device either through uart or i2c interfaces 3.1 i2c interface the registers inside CRTOUCH can be accessed through th e inter-integrated circuit serial interface (i2c, i 2 c, or iic). the i2c interface provides a method of communication with a number of devices and the CRTOUCH can act only as a slave device inside an i2c network, therefore it will respond to read and write operations from a bus ma ster and can never initiate a communication within the bus. to enable the i2c interface, com sel must be tie d high when coming out of reset. CRTOUCH operates as an i2c slave that sends and receives data through the sda line on an i2c bu s. a bus master initiates all data transfers to and from crtouc h, and generates the scl clock that synchronizes the data transfer. the CRTOUCH line operates as an open drain bidirectional signal. a pull-up resistor (typically between 4.7 ? and 10 k ? ) is required on CRTOUCH. for CRTOUCH, scl is an input only signal which also requires an external pull-up. each transmission is initiated with a start condition generated by the master, followed by the CRTOUCH slave address (7 bits) plus one bit that indicates if the transaction is a read or write operation, in the case of write sequen ces it includes one reg ister address byte and 1 to n data bytes for r ead or write transactions, followed by a stop condition that indicates the end of that transmission. serial communications CRTOUCH data sheet, rev. 3 freescale semiconductor 23 figure 16. i2c start and stop conditions and timing 3.1.1 i2c bit transfer because CRTOUCH can operate with different voltages, the levels of the logical low and high valu es are not fixed and depend on the associated level of v dd . the data on the sda line must be stable during the high period of the clock. any change on the sda line for data transmission can only occur when the clock si gnal on the scl line is low. figure 17. bit transfer 3.1.2 i2c start and stop conditions a transition to low on the sda line while scl is high indicates a start (s) condition. a transition to high on the sda line whi le scl is high defines a stop (p) condition. start and stop conditions are always generated by the master. the bus is free when no master device is engaging the bus (both scl and sda are high). when the bus is free, a master may initiate communication by sending a start signal. the bus is considered to be busy after the start condition. the bus is considered to be free again at a certain time after the stop condition. the bus stays busy if a repeated start (sr) is generated instead of a stop condition. the start (s) and repeated start (sr) are functionally identical, th erefore the s symbol will be used as a generi c term to represent both the start and repeated start conditions, unless sr is particularly relevant. figure 18. start and stop conditions CRTOUCH data sheet, rev. 3 serial communications freescale semiconductor 24 3.1.3 i2c transferring data the number of bytes that can be transmitte d per transfer is unrestricted. each byte has to be followed by an acknowledge bit. data is transferred with the mo st significant bit (msb) first. within each byte , there must be 8-data bits and on e acknowledge bit. 3.1.4 i2c acknowledge data transfer with acknowledge is obligatory for the i2c protocol. the acknowledge-related clock pulse is generated by the i2c master as a 9th bit which the recipient uses to handshake rece ption of each byte of data. thus each byte transferred effectivel y requires 9 bits. to acknowledge a byte, the device sending data through the i2c bus releases the CRTOUCH line in the 9th bit of data. in this clock the receiver has to pul l down and maintain the CRTOUCH line stable low during the high period of this clock pulse as an acknowledgement that the byte was received properly. when CRTOUCH does not acknowledge a byte in a transaction it can indicate one of the following conditions: ? the address is trying to be acce ssed (either read or write) does not exist in the memory map ? the location written does not have write attributes if the CRTOUCH does not acknowledge the data byte, the crt ouch line is left high during the acknowledge clock bit and the master has to generate a stop or repeat start condition. figure 19. i2c acknowledge 3.1.5 CRTOUCH i2c slave address the CRTOUCH has a 7-bit long slave address. the eight bit follow ing the slave address is the r/ w bit used to indicate if the transaction is going to be a read or write transaction (low indicat es a write command). the i2c address has a configurable bit through the addrsel signal. when connected to ground, bit 1 of the i2c address will be 0 and 1 when connected to v dd . the resulting two 7 bit addresses possible are: 0x49 and 0x4b. figure 20. i2c slave address serial communications CRTOUCH data sheet, rev. 3 freescale semiconductor 25 3.1.6 message format for writing CRTOUCH a write sequence comprises the transmission of the CRTOUCH slave address with a valu e of 0 for the r/w bit followed by two bytes of information. the first byte of information is the memory map address byte and the second byte is the first data byte t o be written. the memory map section of this document details the address of each register, its read and write permissions and the auto increment address in case more than 1 data byte is written. any byte received after the address byt e is taken as data bytes and is written in the location where the internal memory map logi c points at that moment. a not acknowledge may be generated if the location written does not exist or does not have write permissions. figure 21. i2c write sequence 3.2 uart the CRTOUCH device can also send and receive data through a uart communication. default configuration is 115200 bps, 8 data bits, odd parity and one stop bit. the only configurable parameter is the baud rate through the auto-detection feature. al l the other settings are fixed. to synchronize start and end of transactions with a host devi ce, uart communication uses a start and end of frame reserved characters. all the data within the data payl oad will be sent in unpacked bcd (that is a value of 0 x 8c will be sent in two by tes, 0 x 08 and 0 x 0c) to avoid overlapping with the start and end of frame characters. because there are tx and rx dedicated lin es for the uart communication, for any comm and (read or write) there must be a response from CRTOUCH, either replying to a read transaction or replying a status byte (success or error) from the previous transaction. 3.2.1 uart baudrate auto detection the CRTOUCH comes with an auto detect feature that allows configuring any baudrate from 9600 bps to 115200 bps. to use this feature: 1. baudrate auto detection signal is asserted with a low value. 2. host sends three consecutive bytes with 0 x 55 values with 8-data bits, odd parity, and one stop bit at the desired baudrate to configure. 3. finally new baudrate is configured on CRTOUCH. if the requested baudrate is out of range or the values sent are not the appropriate ones to calculate a valid baudrate the las t valid value stored on the memory map is used and a baudrate error will be indicated in the status error register. CRTOUCH data sheet, rev. 3 serial communications freescale semiconductor 26 3.2.2 uart communication protocol the protocol uses the following format: figure 22. uart protocol format start of frame ? a specific byte that indicates the st art of a communication between a host and CRTOUCH. data byte value 0 x c0 is used for this purpose. register address ? includes information if th ere is a write or read re quest from the mcu host to CRTOUCH, and data record address from the CRTOUCH memory map. data record address is 7-bits width, from bit 6 to bit 0 and write/ read transaction is located on [b7]. b7 low indi cates a read transaction. payload size ? information about quantity of bytes to be read or writte n is included on this field, this size does not include start of frame, register a ddress, nor end of frame. data bytes ? write or read information from the the memory map. the nu mbers of bytes to be read or written specified in the payload size define how many bytes each frame has. section 4.1, ?device memory map ? includes a descript ion of the registers address and the next address to be written or read in case of a sequential read/write operation. end of frame (eof) ? eof indicates that the current co mmunication has been finished. if the data frame transmitted from the host mcu to the CRTOUCH does not incl ude an eof (0 x c1), the information sent from the host to CRTOUCH does not have any effect. when processing data through uart interface th e command is executed upon the reception of an eof. starting on the data record address byte to the last data byte to be transmitted or received by the host mcu, each data byte is divided in msb nibble and lsb nibble where the valid range written goes from 0 x 00 to 0 x 0f. 3.2.3 registers read through uart to read any CRTOUCH register using the uart interface, the communication must st art with a sof followed by a register address with the most significant bit value of ?0? and the amount of bytes that the host wishes to read followed by an eof. upon reception of a read command, CRTOUCH will reply us ing the same uart communication protocol (sof, register address, payload size, data payload, and eof) with the data from the registers read. figure 23. register read through uart communication serial communications CRTOUCH data sheet, rev. 3 freescale semiconductor 27 3.2.4 registers write through uart to write one to n CRTOUCH registers, the communication must st art with a sof, followed by a re gister address with the most significant bit value of ?1? indicating the amount of registers to be written, followed by the data bytes and ending with an eo f. the CRTOUCH will reply either with an acknowledge byte or an error code. figure 24. register write through uart communication the following table shows a list of possible responses to a write commands from a host. response to any write command is the only communication where the communication protocol is not stric tly followed to reduce the amount of traffic generated for a simple acknowledgement. table 6. uart communication responses to a write command byte value information 0xc2 positive acknowledge. the last command data was valid and has been properly written into CRTOUCH. 0xe0 sampling rate out of range. a value between 5 and 100 (ms) is expected. 0xe1 invalid write transaction. register written does not have write attributes 0xe2 data size out of range. a value between 1 and tes sent in the write command 0xe3 register address out of range. see memory map section for more information 0xe5 parity error was generated. parity is odd parity for each byte. table 7. uart communication responses to a write command byte value information 0xc2 positive acknowledge. the last command data was valid and has been properly written into CRTOUCH. 0xe0 sampling rate out of range. a value between 5 and 100 (ms) is expected. 0xe1 invalid write transaction. register written does not have write attributes 0xe2 data size out of range. a value between 1 and test sent in write command 0xe3 register address out of range. see memory map section for more information 0xe5 parity error was generated. parity is odd parity for each byte. CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 28 4 memory map and registers description the CRTOUCH product has status and configuration registers for th e resistive touchscreen driver and the capacitive keys support . all the status registers are read-only regi sters. the configuration regi sters have read and write a ttributes. all configuration registers are stored in non-vol atile memory when changed, th e device therefore does not require reconfiguration after power loss or reset. only specific bits in certain registers are not restored and this is indicated in the corr esponding bit descript ion. when writing a configuration value into a register, it may take one sampling period, resistive or capacitive, for it to take ef fect and to be read. 4.1 device memory map the CRTOUCH memory map is designed to allow a consecutive by tes reading. each register ha s a value for its incremental address, which is the value that the intern al read address pointer hold s after reading that specific location. for example, if the x coordinate is read, the initial transaction starts with addre ss 0x03 and automatically auto-increment to 0x04, 0x05, and 0x06 . when the pressure is disabled, after readi ng the y coordinate lsb in address 0x06, the internal address pointer returns to valu e 0x03 to allow reading again of x and y coor dinates without further write operations. table 8. resistive touch sense status register map name register address incremental address default value valid range comment resistive touch error register 0x00 0x01 0x00 ? used to report serial protocol communication errors resistive touch status register 1 0x01 0x02 0x00 ? register used to report general information resistive touch status register 2 0x02 0x03 0x00 ? register used to report general information x coordinate msb 0x03 0x04 0x00 0x00 ? 0x1f x coordinate msb x coordinate lsb 0x04 0x05 0x00 0x00 ? 0xff x coordinate lsb y coordinate msb 0x05 0x06 0x00 0x00 ? 0x1f y coordinate msb y coordinate lsb 0x06 0x03 1 0x07 2 0x00 0x00 ? 0xff y coordinate lsb pressure value msb 0x07 0x08 0x00 0x00 ? 0xff pressure value msb pressure value lsb 0x08 0x03 0x00 0x00 ? 0xff pressure value lsb resistive touch fifo status 0x09 0x0a 0x00 ? fifo status information fifo x coordinate msb 0x0a 0x0b 0x00 0x00 ? 0x1f fifo x coordinate msb fifo x coordinate lsb 0x0b 0x0c 0x00 0x00 ? 0xff fifo x coordinate lsb fifo y coordinate msb 0x0c 0x0d 0x00 0x00 ? 0x1f fifo y coordinate msb fifo y coordinate lsb 0x0d 0x0a 1 0x0e 2 0x00 0x00 ? 0xff fifo y coordinate lsb fifo pressure value coordinate msb 0x0e 0x0f 0x00 0x00 ? 0xff fifo pressure value coordinate msb memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 29 1.incremental address when pressure detection is disabled. 2.incremental address when pressure detection is enabled. fifo pressure value coordinate lsb 0x0f 0x10 0x00 0x00 ? 0xff fifo pressure value coordinate lsb uart baudrate msb 0x10 0x11 0x01 0x00 ? 0x01 uart baud rate msb byte uart baudrate mid 0x11 0x12 0xc2 0x00 ? 0xff uart baud rate mid byte uart baudrate lsb 0x12 0x13 0x00 0x00 ? 0xff uart baud rate lsb byte device identifier register 0x13 0x14 0x 12 ? identifies mask set of the device. increments with versions of the device. slide displacement 0x14 0x15 0x00 0x00 ? 0xff reports how many steps the user displaced since the initial touch rotate angle 0x15 0x16 0x00 0x00 ? 0xff reports the total angle of the rotate motion since the initial touch zoom size 0x16 0x20 0x00 0x00 ? 0xff reports how much zoom has been exercised by the user table 9. capacitive touch status registers name register address incremental address default value valid range comment electrode status 0x20 0x21 0x00 0x00 ? 0x0f each bit represents the current status of an electrode. capacitive touch faults 0x21 0x22 0x00 0x00 to 0x01 shows the faults generated by the system electrode 0 baseline msb 0x22 0x23 0x0000 0x0000 ? 0x07ff electrode base capacitance. this value may adjust to changes due to electrical and environmental noise. electrode 0 baseline lsb 0x23 0x24 electrode 1 baseline msb 0x24 0x25 0x0000 0x0000 ? 0x07ff electrode base capacitance. this value may adjust to changes due to electrical and environmental noise. electrode 1 baseline lsb 0x25 0x26 electrode 2 baseline msb 0x26 0x27 0x0000 0x0000 ? 0x07ff electrode base capacitance. this value may adjust to changes due to electrical and environmental noise. electrode 2 baseline lsb 0x27 0x28 table 8. resistive touch sense status register map (continued) name register address incremental address default value valid range comment CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 30 electrode3 baseline msb 0x28 0x29 0x0000 0x0000 ? 0x07ff electrode base capacitance. this value may adjust to changes due to electrical and environmental noise. electrode3 baseline lsb 0x29 0x2a electrode0 instant delta 0x2a 0x2b 0x00 -128 ? 127 instant capa citance variation with respect to its baseline electrode1 instant delta 0x2b 0x2c 0x00 -128 ? 127 instant capacitance variation with respect to its baseline electrode2 instant delta 0x2c 0x2d 0x00 -128 ? 127 instant capa citance variation with respect to its baseline electrode3 instant delta 0x2d 0x2e 0x00 -128 ? 127 instant capa citance variation with respect to its baseline slider and rotary dynamic status 0x2e 0x2f 0x00 ? displays the movement, direction, and displacement information slider and rotary static status 0x2f 0x20 0x00 ? displays the touch and absolute position information. holds the invalid position status flag capacitive electrodes fifo 0x30 0x30 0x00 ? register window for keypad fifo. consecutive reads to this register return successive fifo elements. table 10. resistive touch configuration register map name register address incremental address default value valid range comment resistive touch system configuration 0x40 0x41 0x00 0x00 ? 0xff general CRTOUCH configuration register resistive touch trigger events 0x41 0x42 0x00 0x00 ? 0xff register used to select what event shall assert port pin event signal resistive touch fifo setup 0x42 0x43 0x00 0x00 ? 0x1f fifo enabler and watermark are configured in this register sampling rate x and y coordinates (msec) 0x43 0x44 0x05 0x05 ? 0x64 determi nes the resistive touchscreen sampling rate in milliseconds x settling time msb 0x44 0x45 0x0064 0x000e ? 0x012c x settling time high byte x settling time lsb 0x45 0x46 x settling time low byte y settling time msb 0x46 0x47 0x0064 0x000e ? 0x012c y settling time high byte y settling time lsb 0x47 0x48 y settling time low byte z settling time msb 0x48 0x49 0x0064 0x000e ? 0x012c z settling time high byte z settling time lsb 0x49 0x4a z settling time low byte table 9. capacitive touch status registers name register address incremental address default value valid range comment memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 31 display horizontal resolution msb 0x4a 0x4b 0x1000 0x0030 ? 0x2000 msb of the display resolution on the x axis display horizontal resolution lsb 0x4b 0x4c lsb of the display resolution on the x axis display vertical resolution msb 0x4c 0x4d 0x1000 0x1000 0x0030 ? 0x2000 msb of the display resolution on the y axis display vertical resolution lsb 0x4d 0x4e lsb of the display resolution on the y axis resistive touch slide steps 0x4e 0x4f 0x0a 0x01 ? 0xff defines how many slides per axis may be detected table 10. resistive touch configuration register map (continued) name register address incremental address default value valid range comment CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 32 table 11. calibration values registers map name register address incremental address default value valid range comment x calibration value 1 msb 0x4f 0x50 0x4000 0x0000 ? 0xffff manual calibration values. writing to these registers calibrates the device without the need for pressing the calibration points on the touchscreen. x calibration value 1 lsb 0x50 0x51 x calibration value 2 msb 0x51 0x52 0x0 0x0000 ? 0xffff x calibration value 2 lsb 0x52 0x53 x calibration value 3 msb 0x53 0x54 0x0 0x0000 ? 0xffff x calibration value 3 lsb 0x54 0x55 y calibration value 1 msb 0x55 0x56 0x0 0x0000 ? 0xffff y calibration value 1 lsb 0x56 0x57 y calibration value 2 msb 0x57 0x58 0x4000 0x0000 ? 0xffff y calibration value 2 lsb 0x58 0x59 y calibration value 3 msb 0x59 0x5a 0x0 0x0000 ? 0xffff y calibration value 3 lsb 0x5a 0x5b x calibration constant msb 0xb 0x5c 0x0 0x0000 ? 0xffff x calibration constant lsb 0x5c 0x5d y calibration constant msb 0x5d 0x50e 0x0 0x0000 ? 0xffff y calibration constant lsb 0x5e 0x60 memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 33 table 12. capacitive touch configuration registers map name register address incremental address default value valid range comment capacitive system configuration 0x60 0x61 0x20 ? main configuration of the capacitive touch system dc tracker rate 0x61 0x62 0x0a 0x00 ? 0xff determines how often the recalibration function occurs. capacitive touch responsetime 0x62 0x63 0x04 0x00 ? 0x20 configures the number of scans necessary to determine if a key is pressed stuckkeytimeout 0x63 0x64 0x64 0x00 ? 0xff configures the number of scans to detect a key stuck electrode0 sensitivity 0x64 0x65 0x40 0x02 ? 0x7f represents the capacitance threshold for electrode 0 to be detected as touched electrode1 sensitivity 0x65 0x66 0x40 0x02 ? 0x7f represents the capacitance threshold for electrode 1 to be detected as touched electrode2 sensitivity 0x66 0x67 0x40 0x02 ? 0x7f represents the capacitance threshold for electrode 2 to be detected as touched electrode3 sensitivity 0x67 0x68 0x40 0x02 ? 0x7f represents the capacitance threshold for electrode 3 to be detected as touched electrodes enablers 0x68 0x69 0x0f ? eac h bit represents the enabler of an electrode. if a bit is 0, then the corresponding electrode will not be scanned capacitive touch low power scan period 0x69 0x6a 0x0f 0x00 ? 0x0f represents the value of the scan period in low power mode capacitive touch low power electrode 0x6a 0x6b 0x00 0x00 ? 0x03 this register represents the number of the electrode scanned in low power mode low power electrode sensitivity 0x6b 0x6c 0x7f 0x00 ? 0x7f threshold for the low power electrode while in shutdown mode capacitive resolution 0x6c 0x6d 0x0a 0x08 ? 0x0b determines the resolution in bits of the capacitive samples CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 34 4.2 registers description 4.2.1 resistive touch status registers all the resistive touch status registers have read only attributes . attempting to write any of these registers return in an inv alid write response from CRTOUCH. 4.2.1.1 resistive touch error register this register reports several possible failures in th e system. all bits are cleared after a register read capacitive touch events 0x6d 0x6e 0x01 0x00 ? 0xff configures the events that reported by the capacitive controller capacitive touch autorepeatrate 0x6e 0x6f 0xff 0x00 ? 0xff configures the rate at which keys will be reported when kept pressed capacitive touch autorepeatstart 0x6f 0x70 0xff 0x00 ? 0xff configures the time between a touch and an auto-repeat event when the key is kept pressed capacitive maxtouches 0x70 0x71 0x00 0x00 ? 0x03 configures the maximum number of keys that can be pressed at once bit 7 6 5 4 3 2 1 0 field bre ce se wef dse ae eofe pe field description 7 bre baudrate error bre is set when the baud-rate auto detect proc ess can not determine the communication baudrate. 6 ce calibration error flag set when the calibration process can not calculat e the values needed for system calibration. this typically occurs when the points touched do not match with calibration requirements. 5 se sampling error flag set when trying to write the resistive touch sampling rate register with a value less than 5 or more than 100. 4 wef write error flag wef is set when trying to write an address that has read-only attributes. table 12. capacitive touch configuration registers map name register address incremental address default value valid range comment memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 35 3 dse data size error dse is set when number of data = 0 or number of data > 101. 2 ae address error ae is set when the requested address is outsid e the address memory map range or within an un-implemented section of the memory map. 1 eofe end of frame error eof error flag is set to 1 when end of frame is no t received after the communication timeout expires. 0 pe parity error pe error flag is set to 1 when one or several bytes from the received frame does not have odd parity properly configured. field description CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 36 4.2.1.2 resistive touch status register 1 this register reports different events that may be dete cted in the system, and latches some bits to ensure that the event does not get lost if not read immedi ately. latched bits clear af ter a register read. the touchpending pin is also set after this register is read. bit 7 6 5 4 3 2 1 0 field rtst rts2t rtsz rtsr rtss rtsf cte rtsrdy field description 7 rtst resistive touch screen touched is set after any touch event in a resistive screen is connected to CRTOUCH 0 resistive touch screen not currently touched 1 resistive touch screen currently touched 6 rts2t resistive touch screen two touch detection is set after the screen has a two touch detection event. this bit is automatically cleared when a two touch condition is no longer detected on the screen. 0 two touch event not currently detected 1 two touch currently detected. 5 rtsz resistive touch screen zoom indicates when a zoom gesture has been detected. 0 zoom gesture not detected 1 zoom gesture pending for reading 4 rtsr resistive touch screen rotate indicates when a rotate gesture has been detected. 0 rotate gesture not detected 1 rotate gesture pending for reading 3 rtss resistive touch screen slide indicates when a slide gesture has been detected. 0 slide gesture not pending for reading 1 slide gesture pending for reading 2 rtsf resistive touch screen fifo data is set when the fifo count reaches the watermark value or when the fifo is filled. 0 fifo data ful and watermark reached 1 fifo data not full and watermark not reached 1 cte capacitive touch event is set after one of th e configured capacitive events is detected. 0 capacitive touch event not pending for reading 1 capacitive touch event pending for reading 0 rtsrdy resistive touch sample ready is set after a resi stive touch screen connected to CRTOUCH is pressed and the device finished all the data processing to determine x and y coordinates. 0 resistive touch sample not pending for reading 1 resistive touch sample pending for reading memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 37 4.2.1.3 resistive touch status register 2 4.2.1.4 x coordinate bit 7 6 5 4 3 2 1 0 field rtscal reserved rtszd rtsrd rtssd rtsd field description 7 rtscal resistive touch screen calibrated is set after the screen has been properly calibrated. after initial calibration the result is stored in the internal non-volatile memory and is recovered after automatically reset. 0 resistive touch screen not calibrated 1 resistive touch screen calibrated 6 reserved this bit is reserved 5 rtszd zoom direction 0 zoom in 1 zoom out 4 rtsrd resistive touch screen rotate direction. 0 clock wise direction 1 counter clock wise direction 3-2 rtssd resistive touch screen slide direction indicates the direction of the slide gesture after its detection. 0 0 horizontal positive direction 0 1 horizontal negative direction 1 0 vertical positive direction 1 1 vertical negative direction 1-0 rtstd resistive touch screen type detected . after reset, the system scans for the type of resistive touch screen connected to the system. the rtsd bits indicate the type of screen detected. 0 0 resistive touch not detected 0 1 4 wires resistive touch screen detected 1 0 5 wires resistive touch screen detected 1 1 reserved bit 1514131211 10987 6 5 4 3 2 10 field xmsb xlsb CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 38 4.2.1.5 y coordinate 4.2.1.6 pressure value 4.2.1.7 resistive touch fifo status signal description 15-8 xmsb most significant byte for x coordinate 7-0 xlsb least significant byte for x coordinate bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field ymsb ylsb signal description 15-8 ymsb most significant byte fory coordinate 7-0 ylsb least significant byte for y coordinate bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field pressmsb presslsb signal description 15-8 pressmsb most significant byte for pressure detected when touching the screen 7-0 presslsb least significant byte for pressure detected when touching the screen bit 7 6 5 4 3 2 1 0 field reserved reserved fifowmrkf fifowmrkf fifocnt memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 39 4.2.1.8 fifo x coordinate 4.2.1.9 fifo y coordinate 4.2.1.10 fifo pressure value signal description 7 reserved reserved 6 reserved reserved 5 fifowmrkf fifo watermark flag indicates when the fifo c ounter is greater than or equal to the value configured in the watermark bits of the fifo config uration register. 4-0 fifocnt fifo sample counter, default value 00000. (00001 to 11111 indicates 1 to 31 samples stored in fifo) bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field fifoxmsb fifoxlsb signal description 15-8 fifoxmsb most significant byte for x coordinate stored in the fifo 7-0 fifoxlsb least significant byte for x coordinate stored in the fifo bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field fifoymsb fifoylsb signal description 15-8 fifoymsb most significant byte for y coordinate stored in the fifo 7-0 fifoylsb least significant byte for y coordinate stored in the fifo bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field fifopmsb fifoplsb CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 40 4.2.1.11 uart baudrate msb (read only) 4.2.1.12 device identifier register (read only) 4.2.1.13 slide displacement signal description 15-8 fifopmsb most significant byte for pressure stored in the fifo 7-0 fifoplsb least significant byte for pressure stored in the fifo bit 23222120191817161514131211 10 9 8 76543 2 10 field brh brm brl signal description 23-16 fifoymsb most significant byte for uart baudr ate used for the system configuration. 15-8 fifoylsb intermediate byte for uart baudrate used for the system configuration. 7-0 fifoylsb least significant byte for uart baudr ate used for the system configuration. bit 7 6 5 4 3 2 1 0 field deviceid signal description 7-0 deviceid device id stores the product version informat ion. this register is factory programmed and its usage is for traceability purposes. bit 7 6 5 4 3 2 1 0 field slidedata memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 41 4.2.1.14 rotate angle 4.2.1.15 zoom size (read only) 4.2.2 capacitive touch sensing status registers all the capacitive touch sensing status registers have read onl y attributes. attempting to write any of these registers will re turn an invalid write response from CRTOUCH. 4.2.2.1 capacitive electrodes status register signal description 7-0 slidedata reports how many steps the user has displaced after the initial touch. this is useful to keep track of the motion if at lower sampling rates, more than one step was displaced in a sample period. bit 7 6 5 4 3 2 1 0 f i e l d rotat e data signal description 7-0 rotatedata reports the total angle of the rotate motion after the initial touch. bit 7 6 5 4 3 2 1 0 field zoomsize signal description 7-0 zoomsize reports how much zoom has been exercised by the user. bit 7 6 5 4 3 2 1 0 field reserved e3 e2 e1 e0 CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 42 4.2.2.2 capacitive touch faults register 4.2.2.3 electrodes baselines registers 4.2.2.4 electrodes instant delta registers signal description 7-4 reserved reserved 3-0 e3-e0 e3 ? e0 represents the status of the corresponding electrode. a bit set to 1 indicates that the corresponding electrode is detecting a touch event. bit 7 6 5 4 3 2 1 0 field reserved se signal description 7-1 reserved reserved 0 shortened electrode indicates if one of the capacitive elec trodes cannot be measured, typically due to a short to v cc or ground. 1 timeout fault detected 0 no timeout fault detected bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field exbaselinemsb exbaselinelsb signal description 15-8 electrode baseline msb most significant byte for electrodes 0 to 3 baseline. the baseline value is compared to the instant value to determine if the electrode is touched or not. 7-0 electrode baseline lsb least significant byte for electrodes 0 to 3 baseline. the baseline value is compared to the instant value to determine if the electrode is touched or not. bit 7 6 5 4 3 2 1 0 field exinstantdelta memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 43 4.2.2.5 slider and rotary dynamic status 4.2.2.6 slider and rotary static status signal description 7-0 electrode instant delta electrode 3 to electrode 0 instant capacitance variation with respect to its baseline. this register is in signed format, ranging from -128 to 127. if the instant value is greater than these values, the delta value is saturated. bit 7 6 5 4 3 2 1 0 field ctdsmov ctdsdir reserved ctdsval signal description 7 ctdsmov capacitive touch dynamic status movement indicates if movement is being detected at the moment of reading. 1 indicate s that there is movement detected 6 ctdsdir capacitive touch dynamic status direction is used to determine the direction of movement. 1 indicates an incremental movement. this bit remains with its last value even if movement has stop a nd is no longer detected. 5-4 reserved reserved 3-0 ctdsval capacitive touch dynamic status value indicate s the difference in positions from the last status to the new one. this indicates how many positions have been advanced in the current direction of movement. bit 7 6 5 4 3 2 1 0 field ctsstouch ctssinv reserved ctdsval CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 44 note for rotary and sliders, the number of positions is greater than the number of electrodes. the device reports different positions when more th an one electrode is being touched. for more details, review section 2.2.3, ?rotary and slider control ? 4.2.2.7 capacitive electrodes fifo (read only) when electrodes are configured as keypad, capacitive electrodes fifo keep s status information from capacitive electrode 0 to 3. 4.2.3 resistive touch configuration registers all the resistive touch status registers have read and write attr ibutes. care must be taken that the written value is valid for the specific register written 4.2.3.1 resistive and capacitive touch configuration register the resistive and capacitive touch configurat ion register is used to configure the diff erent settings used as part of the resis tive and capacitive scanning processes. all the configuratio n bits except crtshtdwn are non-volatile and recovered to their latest value as part of the part reset sequence. signal description 7 ctsstouch capacitive touch static status touch indicate s if a touch in the control is being detected at the moment of reading. 6 ctssinv capacitive touch static status invalid flag i ndicates if an invalid combination of touched electrodes is being detected. an invalid co mbination is detected when two or more non adjacent electrodes are det ected as touched, for example electrodes 0 and 2. 5- reserved reserved 4-0 ctdsval capacitive touch static status value indicate s the absolute position within the control that is actuated. bit 7 6 5 4 3 2 1 0 field ctfifotouch reserved ctfifokey signal description 7 ctfifotouch capacitive touch fifo touch indicates if the event was a release or a touch event. 1 indicates the key was released 5- reserved reserved 5-0 ctfifokey capacitive touch fifo key determines the key on which the event has occurred memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 45 4.2.3.2 resistive and capacitive triggers register the resistive and capacitive triggers regi ster configures what events will assert the touchpending pin. this can be used to signal to an external host that there is a pending activity to be read in th e status registers. the triggers register also c ontains a bit used by the host to send CRTOUCH into calibration mode?see section 2.1.4, ?calibration process .? all bits except for the calibration bit are non-volatile. a 1 enables the event to a ssert the touchpending pin. bit 7 6 5 4 3 2 1 0 field rtpresen ctcntrl rtslden rtroten rtpncen crtsleep crtshtdwn field description 7 rtpresen resistive touch pressure enable bit is used to enab le the pressure measurement on the resistive touch screen as part of the x and y scanning process. if fi fo is enabled, changing the value of this bit will automatically flush the fifo to synchronize x, y, and pressure buffers. 6-5 ctcntrl capacitive touch control defines the type of contro l used for the four capacit ive electrodes that can be connected to CRTOUCH. ctcntrl 1 ctcntrl 0 configuration 1 1 keypad control selected 1 0 slider control selected 0 1 rotary control selected 0 0 capacitive keys disabled 4 rtslden resistive touch slide enable ? a single touch slide ca n be detected if the x and y coordinates fit in the slide gesture description. status registers 1 and 2 are used to indicate when the slide gesture was detected and the slide direction. 3 rtroten resistive touch rotate enable ? status registers 1 and 2 are used to indicate when the rotate gesture was detected and if it was a clock-wise or counter-clock-wise gesture. 2 rtzmen resistive touch zoom enable ? this bit controls if zoom motions on the touch screen are detected and reported. status registers 1 and 2 are used to indicate when the pinch gesture is detected and if it was a zoom-in or zoom out gesture. 1 crtsleep capacitive resistive touch sleep is used to send the deviceinto sleep mode. section 2.3.2, ?sleep mode ? has detailed information on the CRTOUCH behavior while in sleep mode. 1 sleep mode enabled 0 sleep mode disabled 0 crtshtdwn capacitive resistive touch shutdown is used to configure the CRTOUCH into its lowest power mode available. section 2.3.3, ?shutdown mode ? has detailed information on the CRTOUCH behavior when this bit is enabled. shutdown is the only bi t in the configuration register t hat is not restored after a reset. 1 shutdown mode enabled 0 shutdown mode disabled CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 46 4.2.3.3 fifo setup register any writes to this register will automatica lly flush the fifo of any stored elements. bit 7 6 5 4 3 2 1 0 field rtrel rtcal rtpinch rtsld rtrot rtfifowm ctev rtev field description 7 rtrel resistive touch release bit is used to generate a signal when the resistive touch screen is released. 6 rtcal resistive touch calibration bit sends the CRTOUCH into calibration mode. after this bit is enabled, the system behavior is section 2.1.4, ?calibration process .? writing a 0 to this bit while in a calibration process aborts the calibration. calibration mode is finished after the calibration points have been identified or with a reset. 5 rtzoom resistive touch pinch trigger bit configures the external event pin to be asserted when a zoom-in or zoom out is detected. 4 rtrot resistive touch rotate trigger bit configures the external event pin asserted when a clock-wise or counter-clock-wise rotate gesture is detected. 3 rtsld resistive touch slide trigger bit configures the external event pin asserted when a slide gesture in any direction is detected. 2 rtfifowm resistive touch fifo watermark bit is used to generate a signal after the number of samples in the fifo is greater than or equal to the watermark bits configuration in the fifo setup register 1 ctev capacitive touch event is used to generate a pending activity signal when any capacitive event is detected. capacitive events detection is configured in the capacitive events register. 0 rtev resistive touch event signals the host after each sampling period after the signals have been processed and the coordinates have been determined, as well as any resistive event. bit 7 6 5 4 3 2 1 0 field reserved rtfifoen rtfifowmrk memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 47 4.2.3.4 resistive touch sampling rate this register is used to configure the period to sample the resistive touch screen. 4.2.3.5 x coordinate stabilization time this 16-bit value holds the number needed in micro-seconds for the signals required for an x coor dinate scanning to stabilize. the value is calculated automatically as part of the calibrati on process but can be written through serial communication to simplify factory configuration of devices. field description 7-5 reserved reserved 6 rtfifoen resistive touch fifo enable enables stori ng the resistive touch data inside the fifo. 3-0 rtfifowmrk resistive touch fifo watermark indicates the amount of samples needed to signal an event. when the amount of values stored in the fifo is greater than or equal to the watermark configuration, the rtsf bi t is set in the status register 1. 0 watermark is disabled. fifo event is signaled when the fifo is full. 1?15 fifo event will be signaled when the fifo counter reaches this value. bit 7 6 5 4 3 2 1 0 field rtsampling signal description 7?0 rtsampling value in miliseconds to indicate the scanning period. value must be between 5 and 100 (10 points per second to 200 points per second). bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field xctimesetmsb xctimesetlsb signal description 15?8 x coordinate stabilization msb most significant byte for the x coordinates stabilization delay. 7?0 x coordinate stabilization lsb least significant byte for the x coordinates stabilization delay CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 48 4.2.3.6 y coordinate stabilization time this 16-bit value holds the number needed in micro-seconds for the signals required for a y coordinate scanning to stabilize. the value is calculated automatically as part of the calibrati on process but can be written through serial communication to simplify factory configuration of devices. 4.2.3.7 z coordinate stabilization time this 16-bit value holds the number needed in micro-seconds for the signals required for the pressure coordinate scanning to stabilize. the value is calculated automatically as part of the calibration process, but can be written through serial communication to simplify fact ory configuration of devices. 4.2.3.8 display horizontal resolution determines the resolution for the x coordinates. it is important to configure this value properl y before a calibration is execu ted. values written to this register have no effect until after both horizontal and vertical resolutions have been written. writes t o these registers reset the device calibration. bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field yctimesetmsb yctimesetlsb signal description 15-8 y coordinate stabilization msb most significant byte for the y coordinates stabilization delay. 7-0 y coordinate least significant byte for the y coordinates stabilization delay stabilization lsb bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field ztimesetmsb ztimesetlsb signal description 15-8 pressure stabilization msb most significant byte for the two-touch signals stabilization delay. 7-0 pressure stabilization lsb least significant byte for the tw o-touch signals stabilization delay memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 49 4.2.3.9 display vertical resolution determines the resolution for the y coordinates. it is important to configure this value properl y before a calibration is execu ted. values written to this register have no effect until after both horizontal and vertical resolutions have been written. writes t o these registers reset the device calibration. 4.2.3.10 resistive touch slide steps bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field reserved reserved xaxisresmsb xaxisreslsb signal description 15?14 reserved reserved 13?8 x axis resolution msb most significant byte for the x axis resolution 7?0 x axis resolution lsb least significant byte for the x axis resolution bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field reserved reserved yaxisresmsb ya x i s r e s l s b signal description 15?14 reserved reserved 13?8 y axis resolution msb most significant byte for the y axis resolution 7?0 y axis resolution lsb least significant byte for the y axis resolution bit 7 6 5 4 3 2 1 0 field rtsldsteps CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 50 4.2.4 calibration values registers this set of registers hold the calibration coefficients for the x and y single touch coordinates, as well as the constants for each axis required for two touch gesture calculations. writing to thes e values calibrates the device without the need for touching t he calibration points on the screen. all of the values must be wri tten to calibrate the device. the status register 2 bit for cali bration is set after a reset. 4.2.4.1 x calibration values this set of three 16-bit values represents the calibration coefficients for the x coordinate. to obtain the x coordinate, the f irst value is multiplied by the x sample, the second value by the y sample, and the third value added with the products. 4.2.4.2 y calibration values this set of three 16-bit values represents the calibration coefficients for the y coordinate. to obtain the y coordinate, the f irst value is multiplied by the x sample, the second value by the y sample and the third value added with the products. signal description 7?0 rtsldsteps number of steps reported when a slide is perform side to side of the touch screen bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field xcalxmsb xcalxlsb signal description 15?8 xcalxmsb most significant byte for the x coordinate calibration value. 7?0 xcalxlsb least significant byte for the x coordinate calibration value. bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field xcalxmsb xcalxlsb signal description 15?8 ycalxmsb most significant byte for they coordinate calibration value. 7?0 ycalxlsb least significant byte for the y coordinate calibration value. memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 51 4.2.4.3 x and y two touch constant values these values are used for calculations on two touch gestures. 4.2.5 tss configuration registers 4.2.5.1 capacitive system configuration bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 field x/yconstmsb x/yconstlsb signal description 15?8 x/yconstmsb most significant byte for the x/y tw o touch constant calibration value. 7?0 x/yconstlsb least significant byte for the x/y tw o touch constant calibration value. bit 7 6 5 4 3 2 1 0 field reserved dctrackeren stuckkeyen reserved clpen reserved signal description 7?6 reserved reserved 5 dctrackeren dc tracker enable ? this bit enables the dc tracker to continuously adjust the electrode capacitance baseline. the periodic ity at which the baseline is adjusted is determined by the dc tracker rate. 4 stuckkeyen stuck key enable ? this bit enables the baseline recalibration of a touched electrode after a period of time. if the electrode re mains touched for as long as the stuck key timeout register defines, then the elec trode baseline is recalculated and as a consequence the electrode is released. 3 reserved reserved 2 clpen capacitive low power enable ? this bit enables one of the four electrodes to wake the system from shutdown mode. when this bit is enabled, no electrodes are scanned while in run mode. this bit should be enabled only prior to entering into shutdown mode. this bit is not restored and will always be 0 after a reset. 1?0 reserved reserved CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 52 4.2.5.2 dc tracker rate 4.2.5.3 response time register 4.2.5.4 stuck key timeout register bit 7 6 5 4 3 2 1 0 field dctrackerrate signal description 7?0 dctrackerrate determines how often the recalibration function occurs. this number represents the number of capacitive samples required before recalibration. if this register is set to 0, the dc tracker feature is disabled. 0 dc tracker feature disabled 1?255 dc tracker executed every n sampling period bit 7 6 5 4 3 2 1 0 field reserved resptime signal description 7?6 reserved reserved 5?0 resptime determines the number of measurements required to detect a status change in any electrode. this value represents the number of capaciti ve samples required for an electrode status change detection. 1?32 n measurements to be used bit 7 6 5 4 3 2 1 0 field stuckkeytout signal description 7?0 stuckkeytout determines how many mili-seconds must an electrode be detected as touched before recalibrating that electrode and then detect it as untouched. if this value is set to 0, the stuck key feature is disabled. 0 stuck key feature disabled 1?255 electrode recalibrated after n task executions memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 53 4.2.5.5 electrodes sensitivity this set of registers, one per electrode, holds the sensitivity value of each electrode . sensitivity value is an 8-bit value th at represents the minimum difference betw een an instant reading versus the baseline required to indicate a touch. 4.2.5.6 electrodes enablers this register holds the information of which electro de is enabled. each bi t represents an electrode 4.2.5.7 low power scan period register represents the value of the scan period in the low power mode, this range does not represent a linear (ms) scan interval. bit 7 6 5 4 3 2 1 0 field reserved exsens signal description 7 reserved 6?0 exsens represents the capacitance threshold for an elec trode to be detected as touched, relative to the baseline value of that electrode. 2?127 electrode x (0 to 3) sensitivity bit 7 6 5 4 3 2 1 0 field reserved e3en e2en e1en e0en signal description 3?0 exen 1 ? electrode x enabled 0 ? electrode x disabled bit 7 6 5 4 3 2 1 0 field reserved lpsp CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 54 4.2.5.8 low power electrodes register this register represents the number of th e electrodes scanned in the low power mode. 4.2.5.9 low power electrode sensitivity register signal description 7?4 reserved reserved lpsp determines scan period in low power mode. only selection from the list of predefined values is allowed. 0000 ? 1 ms scan interval 0001 ? 5 ms scan interval 0010 ? 10 ms scan interval 0011 ? 15 ms scan interval 0100 ? 20 ms scan interval 0101 ? 30 ms scan interval 0110 ? 40 ms scan interval 0111 ? 50 ms scan interval 1000 ? 75 ms scan interval 1001 ? 100 ms scan interval 1010 ? 125 ms scan interval 1011 ? 150 ms scan interval 1100 ? 200 ms scan interval 1101 ? 300 ms scan interval 1110 ? 400 ms scan interval 1111 ? 500 ms scan interval bit 7 6 5 4 3 2 1 0 field reserved lpel signal description 7?2 reserved reserved 1?0 lpel low power electrode ? this value selects which of the four electrodes, from e0 ? e3, will be scanned when the system is in shutdown mode and the clpen bit is enabled in the capacitive system configuration register. bit 7 6 5 4 3 2 1 0 field reserved lpsens memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 55 4.2.5.10 capacitive resolution register this register determines the resolution of the capacitive samp les. increasing the capacitive resolution helps improving the sig nal to noise ratio when using thick dielectrics. a re set is needed for this value to take effect. 4.2.5.11 capacitive events register this register is used to configure events for keypad, rotary and slider controls. ea ch bit has a different meaning if the enabl ed control is a keypad, rotary, or slider. signal description 7reserved 6?0 lpsens determines the sensibility value for the low power electrode. bit 7 6 5 4 3 2 1 0 field reserved capres signal description 7?4 reserved reserved 3?0 capres resolution of capacitive samples. 0?7 reserved 8?11 resolution value 12?15 reserved bit 7 6 5 4 3 2 1 0 field reserved relen autorepen hlden moven touchen CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 56 keypad events signal description 7-5 reserved reserved 4 relen release event enabler if this bit is set, the capacitive event bit in th e status register 2 is set when all the electrodes in the control are released. 1 event enabled 0 event disabled 3 autorepen auto repeat enable if this bit is set, the capacitive event bit in the status register 2 will be set at the rate defined by the auto repeat rate register w hen the same electrode remains touched. 1 auto-repeat enabled 0 auto-repeat disabled 2 hlden hold event enabler if this bit is set, the capacitive event bit in the status register 2 will be set when an electrode is first touched and remains touched for the peri od of time defined by the auto repeat start register. the hold event is produced only once , and auto repeat events may be produced after. 1 hold event enabled 0 hold event disabled 1 moven movement event enabler if this bit is set, the capacitive event bit in th e status register 2 will be set when a transition from one position to another is detected. 1 movement event enabled 0 movement event disabled 0 touchen touch event enabler if this bit is set, the capacitive event bit in th e status register 2 will be set when all electrodes are released and an initial touch is detected in any of the electrodes. 1 touch event enabled 0 touch event disabled bit 7 6 5 4 3 2 1 0 field maxkeys buffov reserved keyexen buffoven autorepen relen touchen memory map and registers description CRTOUCH data sheet, rev. 3 freescale semiconductor 57 4.2.5.12 auto repeat rate register signal description 7 maxkeys this bit reflects if the number of keys allowed to be touched at the same time through the max keys register has been exceeded. this bit is automatically cleared when the condition is no longer true. 1 number of key is exceeded 0 number of keys below the configured value 6 buffov this bit reflects if the keypad fifo is full. this bit is automatically cleared with a read of the register. 1 keypad fifo holds 16 events 0 keypad fifo has free elements 5 reserved reserved 4 keyexen if this bit is set, the capaciti ve event bit in the status regist er 2 is set when the maxkeys flag is set. 1 keys exceeded event enabled 0 keys exceeded event disabled 3 buffoven if this bit is set, the capacitive event bit in t he status register 2 is set when the buffov flag is set. 1 buffer overflow event enabled 0 buffer overflow event disabled 2 autorepen if this bit is set, the new touch events are stor ed in the keypad fifo at the rate defined by the autorprate register while the electrode remains touched. 1 touch event auto repeat enabled. 0 touch event auto repeat disabled. 1 relen if this bit is set, electrode release events are stored in the keypad fifo. 1 release events stored in fifo 0 release events not stored in fifo 0 touchen if this bit is set, electrode touch events are stored in the keypad fifo. 1 touch events stored in fifo 0 touch events not stored in fifo bit 7 6 5 4 3 2 1 0 field autorprate signal description 7?0 autorprate auto repeat rate ? sets the rate at which the pr essed keys are reported when kept pressed. if set to 0, no auto-repeat occurs and the event will be automatically disabled in the events register. the user must manually re-enable this event if desired. 0 auto-repeat feature disabled 1?255 touch event reported every n measurements CRTOUCH data sheet, rev. 3 memory map and registers description freescale semiconductor 58 4.2.5.13 auto repeat rate start register 4.2.5.14 max touches register this register defines the maximum number of simultaneous touc hed keys reported by a keypad control. this feature can be used to control the function when a bigger than expected area is touched. for example, a multiplexed array of electrodes where only two keys are needed to detect a value or function. in this cas e, the maxtouches register is co nfigured with a value of two. bit 7 6 5 4 3 2 1 0 field autorpstrt signal description 7?0 autorpstrt auto repeat start sets the time a key must remain pressed befor e generating new events at the auto-repeat rate. if set to 0, the auto-repeat state will be entered immediately after the last touch. 0?255 wait n measurements before auto-repeat. bit 7 6 5 4 3 2 1 0 field reserved maxtouches signal description 7?0 maxtouches maximum number of touches. sets the limit for simultaneous touched keys. if set to 0, no limit is established. 0 no limit established 1?3 limit set to n keys. electrical specifications CRTOUCH data sheet, rev. 3 freescale semiconductor 59 appendix a electrical specifications this chapter contains electri cal and timing specifications. a.1 voltage and current operating requirements 1.the device always interprets an input as a 1 when the input is greater than or equal to vih (min. ) and less than or equal to vih (max.), regardless of whether input hysteresis is turned on. 2. the device always interprets an input as a 0 when the input is less than or equal to vil (max.) and greater than or equal to vil (min.), regardless of whether input hysteresis is turned on. 3. all functional non-supply pins are internally clamped to v ss and v dd . input must be current limited to the value specified. to determine the value of the required curr ent-limiting resistor, calculate resistanc e values for positive and negative clamp voltages, then use the larger of t he two values. power supply must maintain regulation within operating v dd range during instantaneous and operating maximum current co nditions. if positive injection current (v in > v dd ) is greater than i dd , the injection current may flow out of v dd and could result in external power supply going out of regulation. ensure external v dd load will shunt current greater than the maximum injection current. this will be the greatest risk when the mcu is not consuming power. examples are: if no syst em clock is present, or if clock rate is very low (which reduces overall power consumption). symbol description minimum maximum unit v dd supply voltage 1.8 3.6 v v dda analog supply voltage 1.8 3.6 v v dd -v dda v dd to -v dda differential voltage -0.1 0.1 v ss -v ssa v ss to -v ssa differential voltage -0.1 0.1 v ih input high voltage 1 ? 2.7 v vdd 3.6 v ? 1.8 v vdd 2.7 v 0.7 x vdd 0.75 x vdd ? ? v v v il input low voltage 2 ? 2.7 v vdd 3.6 v ? 1.8 v vdd 2.7 v ? ? 0.35 x v dd 0.3 x v dd v v i ic dc injection current ? single pin 3 ? vin > vdd ?vin < vss 0 0 2 ?0.2 ma ma dc injection current ? sum of all stressed pins 3 ? vin > vdd ?vin < vss 0 0 25 ?5 ma ma v oh output high voltage ? 2.7 v vdd 3.6 v, i oh = ?10 ma ? 1.8 v vdd 2.7 v, i oh = ?3 ma vdd ? 0.5 vdd ? 0.5 ? ? v v v ol output low voltage ? 2.7 v vdd 3.6 v, ioh = ?10 ma ? 1.8 v vdd 2.7 v, ioh = ?3 ma ? ? 0.5 0.5 v v t j die junction temperature ?40 125 c t a ambient temperature ?40 105 c CRTOUCH data sheet, rev. 3 electrical specifications freescale semiconductor 60 a.2 uart timing specifications a.3 esd handling ratings 1. determined according to jedec standard jesd22-a114, electrostatic discharge (esd) sensitivity testing human body model (hbm) . 2. determined according to jedec standard jesd22-c101, field-induced charged-device model test method for electrostatic-discharge-withstand thre sholds of microelectronic components . a.4 i2c timing specifications a.5 capacitive electrodes specifications description min typical max unit reading response time ? 57 75 ? s writing response time ? 81 110 ? s auto baudrate pulse width 1.5 ? ? ms time between auto baudrate pulse and first synchronization byte 2? ? ms auto baudrate timeout ? ? 1.1 s symbol description min. max. unit notes v hbm electrostatic discharge voltage, human body model -2000 +2000 v 1 v cdm electrostatic discharge voltage, charged-device model -500 +500 v 2 i latch-up current at ambient temperature of 105c -100 +100 ma description min max unit reading frame duration 214 1700 ? s writing frame duration 300 1800 ? s description min typical max unit electrode capacitance range 1 20 500 pf capacitive electrodes sampling peroid ? 7 ? ms electrical specifications CRTOUCH data sheet, rev. 3 freescale semiconductor 61 a.6 current ratings 1. average current measured with the device in idle state. 2. average current measured while touchi ng the touch screen, with pressure and two touch gestures enabled. a screen with impedances around 600 ?? was used. this value varies depending on the current consumed by the screen when touched. a.7 operating mode transition timing specification 1. valid for power on reset, pin reset and shutdown wakeup. 2. measured when only the shutdown bit is written without prior register writes. 3. measured after writing a series of regi sters before shutdown. time increases due to the time required to store values in non volatile memory. 4. after a falling edge on wake pin. a.8 resistive screen scan times specifications description typical 1 max 2 unit run ? 3.3 v ? 1.8 v 11.8 11.8 14.6 13.7 ma sleep ? 3.3 v ? 1.8 v 0.39 0.39 6.9 6.1 ma shutdown ? 3.3 v ? 1.8 v 1 1 120 61 ? a description min max unit reset ? run 1 ?13 ms run ? sutdown transiton 2 2 550 3 ? s sleep ? run 4 5? ? s wake pulse 10 ? ? s description min typical max unit signal settling time 14 100 300 ? s signal measurement time ? normal mode ? calibration mode ? ? 150 160 ? ? ? s CRTOUCH data sheet, rev. 3 electrical specifications freescale semiconductor 62 a.9 nvm reliability specifications symbol description min typical unit tnvmretee100 data retentio n up to 100% of write endurance 550 years tnvmretee10 data retention up to 10% of write endurance 10 100 years tnvmretee1 data retention up to 1% of write endurance 15 100 years nnvmwree write endurance 315 k 1.6 m writes packing information CRTOUCH data sheet, rev. 3 freescale semiconductor 63 appendix b packing information CRTOUCH data sheet, rev. 3 packing information freescale semiconductor 64 packing information CRTOUCH data sheet, rev. 3 freescale semiconductor 65 CRTOUCH data sheet, rev. 3 packing information freescale semiconductor 66 packing information CRTOUCH data sheet, rev. 3 freescale semiconductor 67 document number: CRTOUCHds rev. 3 04/2013 how to reach us: home page: www.freescale.com web support: http://www.freescale.com/support usa/europe or locations not listed: freescale semiconductor, inc. technical information center, el516 2100 east elliot road tempe, arizona 85284 +1-800-521-6274 or +1-480-768-2130 www.freescale.com/support europe, middle east, and africa: freescale halbleiter deutschland gmbh technical information center schatzbogen 7 81829 muenchen, germany +44 1296 380 456 (english) +46 8 52200080 (english) +49 89 92103 559 (german) +33 1 69 35 48 48 (french) www.freescale.com/support japan: freescale semiconductor japan ltd. headquarters arco tower 15f 1-8-1, shimo-meguro, meguro-ku, tokyo 153-0064 japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com asia/pacific: freescale semiconductor hong kong ltd. technical information center 2 dai king street tai po industrial estate tai po, n.t., hong kong +800 2666 8080 support.asia@freescale.com for literature requests only: freescale semiconductor literature distribution center p.o. box 5405 denver, colorado 80217 1-800-441-2447 or 303-675-2140 fax: 303-675-2150 ldcforfreescalesemiconduc tor@hibbertgroup.com information in this document is provid ed solely to enable system and software implementers to use freescale semiconduc tor products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. freescale semiconductor reserves the right to make changes without further notice to any products herein. freescale semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does freescale semiconductor assume any liability arising out of the application or use of any product or circuit, and specif ically disclaims any and all liability, including without limitation consequential or incidental damages. ?typical? parameters that may be provided in freescale semiconductor data s heets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?typicals?, must be validated for each customer application by customer?s technical experts. freescale semiconductor does not convey any license under its patent rights nor the rights of others. freescale semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applic ations intended to support or sustain life, or for any other application in which the failure of the freescale semiconductor product could create a situation where personal injury or death may occur. should buyer purchase or use freescale semiconductor products for any such unintended or unauthorized application, buyer shall indemnify and hold freescale semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that freescale semiconductor was negligent regarding the design or manufacture of the part. rohs-compliant and/or pb-free versions of freescale products have the functionality and electrical characteristics as thei r non-rohs-compliant and/or non-pb-free counterparts. for further information, see http://www.freescale.com or contact your freescale sales representative. for information on freescale?s environmental products program, go to http://www.freescale.com/epp . freescale? and the freescale logo are trademarks of freescale semiconductor, inc. all other product or service names are the property of their respective owners. ? freescale semiconductor, inc. 2007-2012. all rights reserved. |
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