Crystal Touch User`s Manual
Contents
1. Filler Byte Contents of register Ox1E Read from register 0x1B Filler byte Filler byte Filler byte Filler byte Filler byte Filler byte Contents of register OxOEE Ox9B Write to register 0x1B Filler byte Value amp OxFO 0x08 Set charge time to 1000ns Filler byte Ox9E Write to register Ox1E Filler byte 0x02 Write command Filler byte Read from register 0x1E Filler byte Filler byte Filler byte Filler byte Filler byte Filler Byte Contents of register Ox1E 0x82 Write Status Register OxFB Filler byte 0x00 Clear Status register OxFB Filler byte Write to register 0x03 Filler byte Enable finger tracking Filler byte Write to Calibration Filler byte Start calibration Filler byte Read register 0x02 Filler byte Filler byte Filler byte Filler byte Filler byte Filler byte Status Continue reading register 0x02 until it is non zero 0x82 Write to register 0x02 Filler byte 0x00 Clear status Filler byte 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 12 of 19 User s Manual pe ULAR Crystal Touch DISPLAY YOUR ADVANTAGE 4 5 Register Descriptions 4 6 Status 0x02 e Bit 3 POST Power On Self Test The POST bit indicates successful completion of the power on self test POST following a reset It is cleared by writing to the register2. The signal strength of the finger is called Z level A smaller finger results in a lower Z level and a larger finger gives a larger Z level See section 4 2 Z Level Z level values range from 0 to 63 5 Initialization Crystal Touch performs a power on self test POST and a self calibration following a reset If the POST completes successfully the POST bit in the Status register 0x02 is set and the Data Ready signal is set high 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 16 of 19 D CULAR Crystal Touch User s Manual Once the POST has completed Crystal Touch needs to be set to absolute mode and enabled This is done by writing the value 0x03 to the Control register 0x04 You may also need to invert the X or Y axes which are controlled by the highest two bits in this register see section 4 8 Control 0x04 Next clear the POST bit Data Ready bit and Data ready signal by writing the value 0x00 to the Status register 0x02 If using a 7 panel next change the capacitor charge time to 1000ns see section 4 4 Capacitor Charge Time 6 Power Modes 6 1 Active Mode Active mode is the normal operational mode Crystal Touch defaults to this mode following a power up or reset In this mode Crystal Touch continually scans the touch panel for touches and reports the data To switch from Active mode to Low Power or Shutdown mode
3. set the appropriate bit in the Power and Reset register See 4 7 for more details 6 2 Low Power Mode In Low Power mode Crystal Touch continues to monitor the touch panel for touches When a touch is detected Crystal Touch transitions to Active mode to report the touch Crystal Touch can also be forced back into active mode by setting the bit to 0 Once in Active mode Crystal Touch stays awake until the Low Power or Shutdown bit is set again See 4 7 for more details 6 3 Shutdown Mode Shutdown mode is the lowest power mode available In Shutdown mode Crystal Touch does not respond to any touches Once in Shutdown mode Crystal Touch stays in this mode until the Shutdown bit is set to 0 See 4 7 for more details 7 Coordinate Scaling Although the controller is theoretically capable of returning coordinates between 0 0 and 2047 1535 due to the geometric construction of the touch panels the actual reported coordinates in the corners of the touch panel are typically between 64 64 and 1983 1471 This origin shift must be accounted for when scaling the panel s coordinates to the display s coordinates First shift the reported coordinates to an origin of 0 0 by subtracting 64 from each value Then divide by the maximum coordinate in X and Y Keep in mind that the maximum coordinates should 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd co
4. 1 1 1 1 11 11 post finger down event and data to OS 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 11 1 1 1 1 1 1 1 1 111 111 111 1 if then if else if then 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 19 of 19
5. The POST bit should only be polled if the host cannot access the hardware Data Ready signal see section 7 e Bit 2 DR Data Ready The DR bit indicates when new position data is ready As long as no finger is detected this bit stays low When a finger is detected on the surface of the touch panel this bit is set high every 10ms as long as the finger is present It is cleared by writing to the register The DR bit should only be polled if the host cannot access the hardware Data Ready signal see section 7 NOTE When clearing the Status register a read modify write algorithm is not required Simply write 0x00 to the register to clear it 4 7 Power and Reset 0x03 Table 12 Bit 7 6 5 4 3 2 1 0 Name LP SD RESET Read Write W W R W Initial Value 0 0 0 e Bit 2 LP Low Power The LP bit is used to enter lower power mode After a 1 is written to this bit Crystal Touch will enter low power mode five seconds after the last touch is sensed Power consumption in low power mode is approximately 40uA Crystal Touch will check for a touch every 300ms If a touch is detected or a SPI message is received it will switch back to Active mode Once Crystal Touch enters Low Power mode it can take up to 5ms for it to switch back to Active mode as the result of an incoming SPI message If Crystal Touch is in Low Power mode the host should either send the first message twice with a minimum 5ms spacing between messages or sen
6. WRITE The registers have five bit addresses ranging from 0x00 to 0x1F Commands are formatted as follows Table 5 Register Register Register Register Register Address Address Address Address Address Bit 3 Bit 2 Bit 1 Bit O 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 6 of 19 PCULAR Crystal Touch User s Manual 3 6 3 7 3 8 Register Addresses Only nine of the thirty two registers are used The rest are reserved and should not be read or written Table 6 Register Address Description Status Power and Reset Control Calibrate Z Idle X Position Low Byte Y Position Low Byte X and Y Position High Nibbles Z Level Reading From a Register Reading a register requires four SPI exchanges The host starts by sending the READ command byte The simultaneous response byte may be data from the previous command or it may be a filler byte Three additional bytes need to be sent after the READ byte to give Crystal Touch time to process and respond to the command The response will be sent during the transmission of the final byte When sending one command at a time the three additional bytes must be OxFB OxFB stands for filler byte Example Read the contents of the Status register 0x02 As shown in section 3 3 SPI Inter Message Transfer Delay Crystal Touch require
7. user to effectively move the center of their finger into the corners of the touch panel For this reason your application should not place any small touch areas in the corners of the screen When designing an application to work with a finger actuated touch panel it is recommended that the application avoid creating small touch areas around the outer edges of the display Studies show that for the best possible user experience touch areas should be at least 10mm and should be located at least 5mm from the edge of the screen 1 3 Calibration Each Crystal Touch touch panel undergoes an internal calibration when first powered up This calibration cancels the effects of the panel s construction on all touch measurements Calibration takes around 100ms The operator must not touch the panel during calibration as this could affect measurement sensitivity Once the touch panel is powered up there is no need to execute any subsequent calibration cycles unless the operating parameters of the panel are changed see section 10 Capacitor Charge Time for an example of when this is necessary 2 Hardware Interface 2 1 Signal Descriptions SPI All of Ocular s Crystal Touch touch panels with SPI interface have the following hardware pinout 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 3 of 19 PCULAR 2 2 2 3 2 4 Table 1 Symbol De
8. 4 7 added shutdown bit Added note about Reset on 10 1 touch panel Added 6 Power Modes 5 12 2010 Rev 7 Updated address 8 24 2010 Rev 8 Corrected address in 4 4 Capacitor Charge Time Prepared By Tony Gray Approved By Dave Nolte 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 2 of 19 User s Manual po ULAR Crystal Touch 1 Introduction This document describes the hardware and software interface for Ocular s Crystal Touch touch panels and applies to all Crystal Touch screen sizes 1 1 Theory of Operation Ocular s Crystal Touch touch panels are based on a projected capacitive technology meaning that a capacitive field is projected through a top layer of glass This projection mechanism allows the conductive elements to be embedded inside the glass protecting them from damage The top surface of Ocular s Crystal Touch is a high quality piece of custom glass designed for optimum clarity and hardness When the user places their finger on the glass surface they alter the capacitive field being projected through the glass This alteration is detected and used to determine the location of the user s finger 1 2 Design Considerations The position of the user s finger is determined by calculating the centroid of the changes in the electrical field With some enclosure designs it may be difficult for the
9. G CULAR Crystal Touch User s Manual Crystal Touch User s Manual Table of Contents 1 REENEN eege 3 1 4 Theory of O peration EE 3 1 2 Design Considerations cecccceeeseescecesseeeeeeceneeeseeeeceensnerseceeseeneaeeeeeenenenes 3 T3 ee e EE 3 e ie TEE 3 2 1 Signal Descriptions SPI ssessaseceesesecadeescsctesenen sxessagansedeccecsdsaswactenanne gek geer 3 2 2 PC Interface i cxssudicsnnist acadeascsulnenaiiedastdviinaacclnnadsensciouobdcasnnesanteutecshiossisns 4 23 NDD E 4 2 4 Case Grounds E 4 3 Serial Peripheral Interface PI 4 3 1 Basic OPSTANOM s e a E EE 4 3 2 SPI Timing Ee DEE 5 3 3 SPI Inter Message Transfer Delay ccceceeeeeessseeeeneeeneeeneeeeeees 6 3 4 SPI Slave Select EN 6 3 5 Register Access Protocol Using SPI 2 2 ssceicccccscccnncsnevelecesscecesseieneeclads 6 3 6 ee e E 7 3 7 Reading From a Register zoeereeseseegeggggguENENEde seadueeaewestoctesssansscteneneecsadeees 7 3 8 Pipelining Multiple Reads ssssssseeeeeeer kernerne EEN 8 3 9 Writing Le EC 9 4 Touch Detection pis daw eegene et 10 BN SampleRate EE 10 4 2 Z EE 10 E 10 4 4 Capacitor Charge Time cates e set See de 10 4 5 Register Descriptions u u seeeeeeeeereerr renerne renerne 13 AG Status OXO EE 13 4 7 Power and Reset 0x03 u u u u sseeeeeeerrrrre erne 13 4 8 Control 0x04 sssssssseeeeeeeere renere enlerterede ndedensedet Bebntivekeeec
10. Time Slave Data Hold Time Tacye 2 Master Data Setup Time Tacye 4 Master Data Hold Time Tacye 4 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 5 of 19 CULAR Crystal Touch User s Manual gt n SS_N ACTIVE 6 if INACTIVE ACTIVE Tacye Tsw SCK MISO MOSI Figure 2 SPI Timing 3 3 SPI Inter Message Transfer Delay Crystal Touch requires 50us minimum between transmitted bytes regardless of the baud rate see Trp in Figure 2 Some processors include a settable delay time between bytes For those processors that don t have a settable inter byte delay time or for processors whose maximum inter byte delay time is less than 50us the Crystal Touch software driver will have to enforce the inter byte delay 3 4 SPI Slave Select Line The slave select line must be low for a least one cycle before the first clock of each byte is transferred There is no requirement for the slave select line to toggle between bytes or between packets For example the slave select line can be driven low at power up and stay low forever It can also toggle between each byte as long as it is low for at least one clock cycle before the first clock of each byte 3 5 Register Access Protocol Using SPI Crystal Touch uses a communication method known as Register Access Protocol RAP RAP only has two commands READ and
11. d the first byte of the message followed by a 5ms pause before transmitting the rest of the message 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 13 of 19 User s Manual pe ULA Crystal Touch SPLAY ADVANTAGE e Bit 1 SD Shutdown The SD bit is used to enter shutdown mode After a 1 is written to this bit Crystal Touch will enter shutdown mode immediately Power consumption in shutdown mode is approximately 14A Crystal Touch will not respond to touches in shutdown mode To return to Active mode set the shutdown bit to 0 e Bit 0 RESET Reset Write a 1 to this bit to force a reset of the touch panel controller Follow the standard Initialization process following a reset NOTE Reset is not supported on the 10 1 touch panel 4 8 Control 0x04 Table 13 Name Read Write Initial Value e Bit 7 YINV Y Axis Invert Writing a 0 to this bit results in standard reporting for the Y position data 0 to 1535 Writing a 1 to this bit inverts the Y position data 1535 to 0 The correct setting for this bit depends on the orientation of your Crystal Touch module e Bit 6 XINV X Axis Invert Writing a 0 to this bit results in standard reporting for the X position data 0 to 2047 Writing a 1 to this bit inverts the X position data 2047 to 0 The correct setting for this bit depends on the orientation of y
12. gister 0x14 The response to the fourth OxFC will be the contents of register 0x15 The response to the last byte OxFB will be the contents of register 0x16 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 8 of 19 CULAR Crystal Touch User s Manual Table 8 Command MOSI Response MISO Note 1 OxFB OxFB Contents of register 0x14 Contents of register 0x15 Contents of register 0x16 Note 1 The first response byte may be a filler byte or it may be the response to a previous command 3 11 Writing To a Register 3 12 Writing to a register requires two SPI exchanges The host starts by sending the WRITE command byte The simultaneous response byte may be data from the previous command or it may be a filler byte The host then sends the byte being written to the register The simultaneous response byte is OxFB Multiple writes must be sent as consecutive single writes Example Write the value 0x03 to the Control register 0x04 As shown in 3 3 SPI Inter Message Transfer Delay Crystal Touch requires 50us minimum between transmitted bytes regardless of the baud rate see TTD in Figure 2 Some processors include a settable delay time between bytes For those processors that don t have a settable inter byte delay time or for processors whose maximum inter byte delay time is less than 50us the Crystal Touch software driver
13. iees ali 14 49 Zde 0X0A sena E 15 4 10 Calibrate LA EE 15 4 11 Touch Position Data 0x14 0x15 and 0X16 c esesesseeteteee tenes 15 e Ek Me ai RA a Kg d 16 ET EE 16 6 Power e 17 Ech Active MOG eebe Ee breede geg euer get 17 6 2 Low Power Mode EE 17 6 3 Shutdown Mode EE 17 T Coordinate ee knee et err ee ee 17 8 Data Ready eeneg Deag Egbert Eeer 18 Product descriptions and specifications are subject to change without notice 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 1 of 19 User s Manual po U LAR Crystal Touch Date Page Summary 4 30 2009 Rev 1 Preliminary Release 5 7 2009 Rev 2 Added X and Y axes inversion 8 17 2009 Rev 3 Added calibration and electrical sections Added warning to use read modify write algorithm Added minimum SPI frequency of 420kHz Added section on setting 1000ns charge time Changed maximum SPI frequency to 4MHz Added Reset bit to Power Reset register Corrected table for register address 0x16 1 11 2009 Rev 4 Added current and temperature specs Moved electrical characteristics voltage option quality assurance and mechanical characteristics sections to individual datasheets 2 22 2010 Rev 5 Added 2 3 Vpp Added 2 4 Case Ground Added 6 Coordinate Scaling 3 17 2010 Rev 6 Added 3 3 SPI Inter Message Transfer Delay Added 3 4 SPI Slave Select Line In
14. m Page 17 of 19 PE ULAR 8 Data also be shifted by 64 meaning that the maximum X value is 1983 64 1919 the maximum Y value is 1471 64 1407 The following example scales the panel coordinates to a 16 9 display with a width X of 533 and a height Y of 300 check for underflow if PanelX lt 64 PanelX 0 lse PanelX 64 if PanelY lt 64 PanelY 0 lse PanelY 64 scale coordinates DisplayX PanelX 533 1919 1919 Ss 2047 128 DisplayY PanelY 300 1407 1407 1535 128 check for overflow if DisplayX gt 532 DisplayxX if DisplayY gt 299 DisplayyY 532 299 Note the underflow check on the panel coordinates and the overflow check on the display coordinates This is required because the panel might report coordinates slightly less than 64 64 or slightly greater than 1983 1471 Ready In addition to the Data Ready software flag in the Status register 0x02 there is also a Data Ready hardware signal DR Crystal Touch drives this signal high when new position data is available New position data may be available as often as every 10ms Once the new data has been read write 0x00 to the Status register 0x02 to clear the DR signal This signal also indicates that a Power On Self Test POST has completed successfully following a reset See section 5 Initialization 12700 Park Central Suite 750 Dallas TX 75251 con
15. our Crystal Touch module e Bit 1 AIR Absolute Relative Mode Writing a 0 to this bit puts Crystal Touch in Relative mouse mode Writing a 1 to this bit puts Crystal Touch in Absolute mode Ocular recommends always using Absolute mode e Bit 0 EN Enable Writing a O to this bit disables Crystal Touch Writing a one to this bit enables Crystal Touch 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 14 of 19 User s Manual pe U LAR Crystal Touch DISPLAY YOUR ADVANTAGE 4 9 Z Idle 0x0A Table 14 ee 7 65 aT tT tt oo Name Z Read Write R W Initial Value 0x1E 30 e Bits 7 to 0 ZI Z Idle The number in this register defines how many times Crystal Touch will present empty position data to the host after the finger has been lifted from the touch panel An empty position is defined as both the X and Y positions set to 0 Because new packets are ready every 10ms tap times can be calculated easily by counting the number of empty packets received following a touch When set to 0 this register prevents any empty packets from being sent In this case the position registers will contain the last sensed location until a new finger presence is detected 4 10 Calibrate 0x07 Table 15 Read Write Initial Value e Bit 0 CAL Calibrate Writing a 1 to this bit forces a self calibration cycle Calibration
16. s 50us minimum between transmitted bytes regardless of the baud rate see TTD in Figure 2 Some processors include a settable delay time between bytes For those processors that don t have a settable inter byte delay time or for processors whose maximum inter byte delay time is less than 50us the Crystal Touch software driver will have to enforce the inter byte delay SPI Slave Select Line The slave select line must be low for a least one cycle before the first clock of each byte is transferred There is no requirement for the slave select line to toggle between bytes or between packets For example the slave select line can be driven low at power up and stay low forever It can also toggle between each byte as long as it is low for at least one clock cycle before the first clock of each byte Register Access Protocol Using SPI a Read command is formatted as 101xxxxx OxAX When OR ed with the register address the value is OxA2 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 7 of 19 C CULAR Crystal Touch User s Manual OxAO 0x02 CA Send OxA2 followed by OxFB three times The response to the third OxFB byte will be the contents of register 0x02 Table 7 Command MOSI Response MISO Note 1 OxFB OxFB Contents of register 0x02 Note 1 The first response byte may be a filler byte or it may be the respon
17. s and there is new data to report the touch data registers will be updated every 10ms If the Data Ready bit is not cleared the new data is discarded 4 2 Z Level The Z level is a measure of how much the capacitive field has changed When no finger is near the touch panel the Z level will be at or near 0 Asa finger approaches the top of the touch panel the Z level will begin to increase The Z level will continue to increase as more of the surface area of the finger comes into contact with the top surface of the touch panel Position data is generated for any Z level greater than 0 Therefore it is up to the software driver to determine the minimum Z levels that constitute a touch and a release For more information see Appendix A Software Driver Sample 4 3 Z Idle Once the finger is removed Crystal Touch can be configured to either immediately cease sending position data or it can send a specified number of empty packets This feature is referred to as Z Idle If configured to send empty packets the Data Ready signal will be asserted every 10ms until all the empty packets have been generated 4 4 Capacitor Charge Time The default time that the capacitors in the panel are allowed to charge up is 500ns This default value works correctly for all touch panels except the 7 diagonal touch panel For 7 touch panels the capacitor charge time must be changed to 1000ns Changing the capacitor charge time involves reading and wri
18. scription SPI Clock SPI Master In Slave Out SPI Select Data Ready SPI Master Out Slave In Ground Power Supply Ground Stylus input Ground e 2 3 4 5 6 7 8 9 j CH The mating connector part is Molex 52207 1060 or equivalent The signals are described below SCK MISO SS N MOSI These pins are part of the SPI communications interface See section 2 3 for details SNSN This pin is for a dedicated stylus input Leave this pin unconnected contact Ocular for details on using Crystal Touch with a stylus PC Interface An IC interface is available as an alternative to the standard SPI interface For information on the DC interface refer to the Crystal Touch DC Addendum Vbo It is important that the power supply provided to the touch panel be relatively clean particularly in the low frequency range of 1kHz to 500kHz Noise on the power supply or GND lines can affect the accuracy of the touch panel Case Ground If the system enclosure is metal the touch panel GND must be connected to the case ground 3 Serial Peripheral Interface SPI 3 1 Basic Operation SPI communication is a four wire bus that includes a slave select line for communicating with multiple devices on the SPI bus The Crystal Touch controller is designed as a slave device with a select line two data lines and a clock line see Figure 1 The SPI clock signal SCK must be initialized to low when idle To ac
19. se to a previous command 3 9 Pipelining Multiple Reads Multiple reads can be pipelined for greater throughput by using the auto increment command OxFC in place of the filler byte OxFB Example Read the contents of the Position registers 0x14 through 0x16 As shown in 3 3 SPI Inter Message Transfer Delay Crystal Touch requires 50us minimum between transmitted bytes regardless of the baud rate see TTD in Figure 2 Some processors include a settable delay time between bytes For those processors that don t have a settable inter byte delay time or for processors whose maximum inter byte delay time is less than 50us the Crystal Touch software driver will have to enforce the inter byte delay 3 10 SPI Slave Select Line The slave select line must be low for a least one cycle before the first clock of each byte is transferred There is no requirement for the slave select line to toggle between bytes or between packets For example the slave select line can be driven low at power up and stay low forever It can also toggle between each byte as long as it is low for at least one clock cycle before the first clock of each byte Register Access Protocol Using SPI a Read is formatted as 101xxxxx OxAX When OR ed with the first register address the value is OxB4 OxAO 0x14 OxB4 Send 0xB4 followed by OxFC four times Then send a single OxFB to terminate the sequence The response to the third OxFC will be the contents of re
20. tact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 18 of 19 Crystal Touch User s Manual CX P CULAR Crystal Touch User s Manual DISPL Appendix A Software Driver Sample The following sample code demonstrates how to use the Z level to determine when a touch and release event occur bool TouchPanelDataIsReady void struct POSITION_DATA uintl6 X Y uint8 ZLevel 1 void GetFingerPosition struct POSITION DATA Position These are typical numbers You made need to tune them to your application and enclosure define MIN Z LEVEL FOR TOUCH 25 define Z LEVEL RELEASE THRESHOLD 20 static bool FingerIsPresent FALSE if TouchPanelDatalIsReady struct POSITION DATA FingerPosition GetFingerPosition amp FingerPosition if FingerIsPresent if FingerPosition ZLevel lt Z LEVEL RELEASE THRESHOLD FingerIsPresent FALSE JULI L ULLA LL ATTA TTA AAT post finger up event to OS JULLDLLLLLL ILL LL LL LL LL LL LL LL LL LL if then else dddddddddddddddddddddddd dd dd dd post finger position data to OS ddddddddddddddddddddd dd dd dd dd dd if else if then else if PositionData ZLevel gt MIN Z LEVEL FOR TOUCH FingerIsPresent TRUE 11 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1
21. takes approximately 100ms When calibration is complete the POST bit in the Status register will be set The Status register must be cleared to continue normal operation 4 11 Touch Position Data 0x14 0x15 and 0x16 Table 16 Read Write Initial Value e Address 0x14 Bits 7 to 0 XDLB X Position Low Byte The lower eight bits of the twelve bit X position data 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 15 of 19 User s Manual ZS CULAR Crystal Touch 4 12 Table 17 Read Write Initial Value e Address 0x15 Bits 7 to 0 YDLB Y Position Low Byte The lower eight bits of the twelve bit Y position data Table 18 Name Read Write Initial Value e Address 0x16 Bits 7 to 4 YPHN Y Position High Nibble The upper four bits of the twelve bit Y position data e Address 0x16 Bits 3 to 0 XPHN X Position High Nibble The upper four bits of the twelve bit X position data For all Crystal Touch touch panels the X coordinate ranges from 0 to 2047 and the Y coordinate ranges from 0 to 1535 It is the hosts responsibility to scale these values to the display resolution being used Z Level 0x17 Bit f 7 Table 19 C Name Read Write e Bits 5 to 0 ZL Z Level In addition to X and Y position data Crystal Touch measures finger presence on the touch panel surface
22. ting several two byte extended register addresses Reading and writing an extended address is accomplished by writing the two bytes of the address to a pair of standard registers then writing a command to a third register Each extended memory 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 10 of 19 User s Manual po ULAR Crystal Touch access takes several milliseconds to process Note that the POST bit in the Status register needs to be cleared after each extended memory access To change the capacitor charge time to 1000ns write 0x08 to extended memory address OxOEE This can be accomplished by transmitting the following sequence of bytes to the Crystal Touch touch panel 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 11 of 19 User s Manual po ULAR Crystal Touch Table 10 Description MISO Description 0x83 Write to register 0x03 OxFB Filler byte 0x08 Disable finger tracking OxFB Filler byte Ox9C Write to register Ox1C OxFB Filler byte 0x00 Upper address byte OxFB Filler byte Ox9D Write to register 0x1D OxFB Filler byte OxEE Lower address byte OxFB Filler byte Ox9E Write to register Ox1E OxFB Filler byte 0x01 Read command OxFB Filler byte Read from register Ox1E Filler byte Filler byte Filler byte Filler byte Filler byte
23. tivate Crystal Touch s SPI bus pull the slave select line low SS_N Data sent by the master is placed on the Master Out Slave In line MOSI Data returned by Crystal Touch is placed on the Master In Slave Out line MISO Both sets of data are latched on the falling edge of SCK 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 4 of 19 Crystal Touch User s Manual G Crystal Touch CULAR User s Manual 3 2 Data is presented Most Significant Byte first MSB Crystal Touch s SPI bus supports data rates up to 4Mhz SCK must be low wna SS_N must be low during SS_N transitions to low transmission of entire byte H MOS and MISO transition Be MOS and MISO are V on the rising edge of SCK sampled on the falling MSE is sent first edge of SCK Figure 1 SPI Signals SPI Timing Requirements Timing for the SPI data lines is shown below see Figure 2 The data exchange is started when the master pulls the SS_N line low Due to the full duplex nature of the SPI bus Crystal Touch always returns data at the same time that it is receiving data The returned byte may be data from the previous command or it may be a filler byte Table 4 Symbol Frequency 0 42 Period 0 25 Clock High or Low Time Tacyc 2 Chip Select Lag Time 0 030 Inter Message Transfer Delay 50 Chip Select Lead Time Tacyc Slave Data Valid
24. will have to enforce the inter byte delay SPI Slave Select Line The slave select line must be low for a least one cycle before the first clock of each byte is transferred There is no requirement for the slave select line to toggle between bytes or between packets For example the slave select line can be driven low at power up and stay low forever It can also toggle between each byte as long as it is low for at least one clock cycle before the first clock of each byte Register Access Protocol Using SPI a Write is formatted as 100xxxxx 0x8X When OR ed with the register address the value is 0x84 0x80 0x04 0x84 Send 0x84 followed by 0x03 12700 Park Central Suite 750 Dallas TX 75251 contact OcularLcd com Tel 972 437 3888 Fax 972 437 2562 www OcularLcd com Page 9 of 19 User s Manual po U LAR Crystal Touch Table 9 Command MOSI Response MISO 1 0x84 Note 1 2 0x03 OxFB Note 1 The first response byte may be a filler byte or it may be the response to a previous command NOTE Many registers contain reserved bits that are not used for this application Changing any reserved bits could result in unexpected behavior When writing to a register always use a read modify write algorithm that preserves the values of all reserved bits 4 Touch Detection 4 1 Sample Rate Crystal Touch samples the touch panel 100 times per second or every 10ms If the Data Ready bit is cleared between scan
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