AR1000 Series Resistive
`Touch Screen Controller
`Data Sheet
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B
`
`

`
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`
`QUALITY MANAGEMENT SYSTEM
`CERTIFIED BY DNV
`== ISO/TS 16949 ==
`
`Trademarks
`The Microchip name and logo, the Microchip logo, dsPIC,
`KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,
`PIC32 logo, rfPIC and UNI/O are registered trademarks of
`Microchip Technology Incorporated in the U.S.A. and other
`countries.
`FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
`MXDEV, MXLAB, SEEVAL and The Embedded Control
`Solutions Company are registered trademarks of Microchip
`Technology Incorporated in the U.S.A.
`Analog-for-the-Digital Age, Application Maestro, chipKIT,
`chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net,
`dsPICworks, dsSPEAK, ECAN, ECONOMONITOR,
`FanSense, HI-TIDE, In-Circuit Serial Programming, ICSP,
`Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB,
`MPLINK, mTouch, Omniscient Code Generation, PICC,
`PICC-18, PICDEM, PICDEM.net, PICkit, PICtail, REAL ICE,
`rfLAB, Select Mode, Total Endurance, TSHARC,
`UniWinDriver, WiperLock and ZENA are trademarks of
`Microchip Technology Incorporated in the U.S.A. and other
`countries.
`SQTP is a service mark of Microchip Technology Incorporated
`in the U.S.A.
`All other trademarks mentioned herein are property of their
`respective companies.
`© 2009-2012, Microchip Technology Incorporated, Printed in
`the U.S.A., All Rights Reserved.
` Printed on recycled paper.
`
`ISBN: 9781620761366
`
`Microchip received ISO/TS-16949:2009 certification for its worldwide
`headquarters, design and wafer fabrication facilities in Chandler and
`Tempe, Arizona; Gresham, Oregon and design centers in California
`and India. The Company’s quality system processes and procedures
`are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
`devices, Serial EEPROMs, microperipherals, nonvolatile memory and
`analog products. In addition, Microchip’s quality system for the design
`and manufacture of development systems is ISO 9001:2000 certified.
`
`DS41393B-page 2
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH
`SCREEN CONTROLLER
`
`AR1000 Series Resistive Touch Screen Controller
`
`Special Features:
`• RoHS Compliant
`• Power-Saving Sleep mode
`• Industrial Temperature Range
`• Built-in Drift Compensation Algorithm
`• 128 Bytes of User EEPROM
`
`Power Requirements:
`• Operating Voltage: 2.5-5.0V ±5%
`• Standby Current:
`- 5V: 85 uA, typical; 125 uA (maximum)
`- 2.5V: 40 uA, typical; 60 uA (maximum)
`• Operating “No touch” Current:
`- 3.0 mA (typical)
`• Operating “Touch” Current:
`- 17 mA, typical, with a touch sensor having
`200 layers.
`- Actual current is dependent on the touch
`sensor used
`• AR1011/AR1021 Brown-Out Detection (BOR) set
`to 2.2V.
`
`Touch Modes:
`• Off, Stream, Down, Up and more.
`
`Touch Sensor Support:
`• 4-Wire, 5-Wire and 8-Wire Analog Resistive
`• Lead-to-Lead Resistance: 50-2,000typical)
`• Layer-to-Layer Capacitance: 0-0.5 uF
`• Touch Sensor Time Constant: 500 us (maximum)
`
`Touch Resolution:
`• 10-bit Resolution (maximum)
`
`Touch Coordinate Report Rate:
`• 140 Reports Per Second (typical) with a Touch
`Sensor of 0.02 uF with 200 Layers
`• Actual Report Rate is dependent on the Touch
`Sensor used.
`
`Communications:
`• SPI, Slave mode, p/n AR1021
`• I2CTM, Slave mode, p/n, AR1021
`• UART, 9600 Baud Rate, p/n AR1011
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 3
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`Table of Contents
`1.0 Device Overview .......................................................................................................................................................................... 5
`2.0
`Basics of Resistive Sensors ......................................................................................................................................................... 7
`3.0 Hardware.................................................................................................................................................................................... 11
`I2C Communications .................................................................................................................................................................. 17
`4.0
`5.0
`SPI Communications.................................................................................................................................................................. 21
`6.0 UART Communications.............................................................................................................................................................. 25
`7.0
`Touch Reporting Protocol........................................................................................................................................................... 27
`8.0 Configuration Registers.............................................................................................................................................................. 29
`9.0 Commands ................................................................................................................................................................................. 35
`10.0 Application Notes ....................................................................................................................................................................... 45
`11.0 Electrical Specifications.............................................................................................................................................................. 51
`12.0 Packaging Information................................................................................................................................................................ 53
`Appendix A: Revision History............................................................................................................................................................... 63
`Appendix B: Device Differences........................................................................................................................................................... 64
`Index .................................................................................................................................................................................................... 65
`The Microchip Web Site ....................................................................................................................................................................... 67
`Customer Change Notification Service ................................................................................................................................................ 67
`Customer Support................................................................................................................................................................................ 67
`Reader Response ................................................................................................................................................................................ 68
`
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`
`DS41393B-page 4
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`Applications
`1.1
`The AR1000 Series is designed for high volume, small
`form factor touch solutions with quick time to market
`requirements – including, but not limited to:
`• Mobile communication devices
`• Personal Digital Assistants (PDA)
`• Global Positioning Systems (GPS)
`• Touch Screen Monitors
`• KIOSK
`• Media Players
`• Portable Instruments
`• Point of Sale Terminals
`
`DEVICE OVERVIEW
`1.0
`The Microchip mTouchTM AR1000 Series Resistive
`Touch Screen Controller is a complete, easy to
`integrate, cost-effective and universal touch screen
`controller chip.
`The AR1000 Series has sophisticated proprietary
`touch screen decoding algorithms to process all touch
`data, saving the host from the processing overhead.
`Providing filtering capabilities beyond that of other
`low-cost devices, the AR1000 delivers reliable, vali-
`dated, and calibrated touch coordinates.
`Using the on-board EEPROM, the AR1000 can store
`and independently apply the calibration to the touch
`coordinates before sending them to the host. This
`unique combination of features makes the AR1000 the
`most resource-efficient touch screen controller for
`system designs,
`including embedded
`system
`integrations.
`
`FIGURE 1-1:
`
`BLOCK DIAGRAM
`
`FIGURE 1-2:
`
`PIN DIAGRAM
`
`AR1000 Series (SSOP, SOIC)
`
`AR1000 Series (QFN)
`
`X+
`5WSX-
`Y-
`Y+
`SX+
`
`15
`14
`13
`12
`11
`
`16
`17
`18
`19
`20
`
`X-
`VSS
`VDD
`M1
`SY-
`
`SDI/SDA/RX
`NC
`SCK/SCL/TX
`NC
`SDO
`
`0
`67891
`
`M2
`WAKE
`SIQ
`SY+
`SS
`
`12345
`
`VSS
`X-
`X+
`5WSX-
`Y-
`Y+
`SX+
`SDI/SDA/RX
`NC
`SCK/SCL/TX
`
`20
`19
`18
`17
`16
`15
`14
`13
`12
`11
`
`VDD
`M1
`SY-
`M2
`WAKE
`SIQ
`SY+
`SS
`SDO
`NC
`
`1234567891
`
`0
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 5
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`TABLE 1-1:
`
`PIN DESCRIPTIONS
`Pin
`
`SSOP, SOIC
`1
`2
`3
`
`QFN
`18
`19
`20
`
`4
`
`5
`6
`
`7
`
`8
`
`9
`
`10
`
`11
`
`12
`
`13
`
`14
`
`15
`16
`17
`
`18
`19
`20
`
`1
`
`2
`3
`
`4
`
`5
`
`6
`
`7
`
`8
`
`9
`
`10
`
`11
`
`12
`13
`14
`
`15
`16
`17
`
`Function
`
`Description/Comments
`
`VDD
`M1
`SY-
`
`M2
`
`WAKE
`SIQ
`
`SY+
`
`SS
`
`SDO
`
`NC
`
`SCK/SCL/TX
`
`NC
`
`SDI/SDA/RX
`
`SX+
`
`Y+
`Y-
`5WSX-
`
`X+
`X-
`VSS
`
`Supply Voltage
`Communication Selection
`Sense Y- (8-wire). Tie to VSS, if
`not used.
`4/8-wire or 5-wire Sensor
`Selection
`Touch Wake-up/Touch Detection
`LED Drive/SPI Interrupt. No
`connect, if not used.
`Sense Y+ (8-wire). Tie to VSS, if
`not used.
`Slave Select (SPI). Tie to VSS, if
`not used.
`SPI Serial Data Output/I2C™
`Interrupt. Tie to Vss, if UART.
`No connection. No connect or tie
`to VSS or VDD.
`SPI/I2C™ Serial Clock/UART
`Transmit
`No connection. No connect or tie
`to VSS or VDD.
`I2C™ Serial Data/SPI Serial Data
`Input/UART Receive
`Sense X+ (8-wire). Tie to VSS, if
`not used.
`Y+ Drive
`Y- Drive
`5W Sense (5-wire)/Sense X-
`(8-wire). Tie to VSS, if not used.
`X+ Drive
`X- Drive
`Supply Voltage Ground
`
`DS41393B-page 6
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`2.0
`
`BASICS OF RESISTIVE
`SENSORS
`
`Terminology
`2.1
`ITO (Indium Tin Oxide) is the resistive coating that
`makes up the active area of the touch sensor. ITO is a
`transparent semiconductor that is sputtered onto the
`touch sensor layers.
`Flex or Film or Topsheet is the top sensor layer that a
`user touches. Flex refers to the fact that the top layer
`physically flexes from the pressure of a touch.
`Stable or Glass is the bottom sensor layer that
`interfaces against the display.
`Spacer Adhesive is a frame of adhesive that connects
`the flex and stable layers together around the perimeter
`of the sensor.
`Spacer Dots maintain physical and electrical
`separation between the flex and stable layers. The dots
`are typically printed onto the stable layer.
`
`Bus Bars or Silver Frit electrically connect the ITO on
`the flex and stable layers to the sensor’s interface tail.
`Bus bars are typically screen printed silver ink. They
`are typically much lower in resistivity than the ITO.
`X-Axis is the left and right direction on the touch sensor.
`Y-Axis is the top and bottom direction on the touch
`sensor.
`Drive Lines supply a voltage gradient across the
`sensor.
`
`General
`2.2
`Resistive 4, 5, and 8-wire touch sensors consist of two
`facing conductive layers, held in physical separation
`from each other. The force of a touch causes the top
`layer to deflect and make electrical contact with the
`bottom layer.
`Touch position measurements are made by applying a
`voltage gradient across a layer or axis of the touch
`sensor. The touch position voltage for the axis can be
`measured using the opposing layer.
`A comparison of typical sensor constructions is shown
`below in Table 2-1.
`
`TABLE 2-1:
`Sensor
`
`SENSOR COMPARISON
`
`Comments
`
`4-Wire
`
`5-Wire
`
`8-Wire
`
`Less expensive than 5-wire or 8-wire
`Lower power than 5-wire
`More linear (without correction) than 5-wire
`Touch inaccuracies occur from flex layer damage or resistance changes
`Maintains touch accuracy with flex layer damage
`Inherent nonlinearity often requires touch data correction
`Touch inaccuracies occur from resistance changes
`More expensive than 4-wire
`Lower power than 5-wire
`More linear (without correction) than 5-wire
`Touch inaccuracies occur from flex layer damaged
`Maintains touch accuracy with resistance changes
`The AR1000 Series Resistive Touch Screen
`Controllers will work with any manufacturers of analog
`resistive 4, 5 and 8-wire
`touch screens. The
`communications and decoding are included, allowing
`the user the quickest simplest method of interfacing
`analog resistive touch screens into their applications.
`The AR1000 Series was designed with an
`understanding of the materials and processes that
`make up resistive touch screens. The AR1000 Series
`Touch Controller is not only reliable, but can enhance
`the reliability and longevity of the resistive touch
`screen, due to its advanced filtering algorithms and
`wide range of operation.
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 7
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`4-Wire Sensor
`2.3
`A 4-wire resistive touch sensor consists of a stable and
`flex layer, electrically separated by spacer dots. The
`layers are assembled perpendicular to each other. The
`touch position is determined by first applying a voltage
`gradient across the flex layer and using the stable layer
`to measure the flex layer’s touch position voltage. The
`second step is applying a voltage gradient across the
`stable layer and using the flex layer to measure the
`stable layer’s touch position voltage.
`The measured voltage at any position across a driven
`axis is predictable. A touch moving in the direction of
`the driven axis will yield a linearly changing voltage. A
`touch moving perpendicular to the driven axis will yield
`a relatively unchanging voltage (See Figure 2-1).
`
`FIGURE 2-1:
`
`4-WIRE DECODING
`
`DS41393B-page 8
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`8-Wire Sensor
`2.4
`An 8-wire resistive touch sensor consists of a stable
`and flex layer, electrically separated by spacer dots.
`The layers are assembled perpendicular to each other.
`The touch position is determined by first applying a
`voltage gradient across the flex layer and using the
`stable layer to measure the flex layer’s touch position
`voltage. The second step is applying a voltage gradient
`across the stable layer and using the flex layer to
`measure the stable layer’s touch position voltage.
`The measured voltage at any position across a driven
`axis is predictable. A touch moving in the direction of
`the driven axis will yield a linearly changing voltage. A
`touch moving perpendicular to the driven axis will yield
`a relatively unchanging voltage.
`
`FIGURE 2-2:
`
`8-WIRE DECODING
`
`The basic decoding of an 8-wire sensor is similar to a
`4-wire. The difference is that an 8-wire sensor has four
`additional interconnects used to reference sensor
`voltage back to the controller.
`A touch system may experience voltage losses due to
`resistance changes in the bus bars and connection
`between the controller and sensor. The losses can vary
`with product use, temperature, and humidity. In a
`4-wire sensor, variations in the losses manifest them-
`selves as error or drift in the reported touch location.
`The four additional sense lines found on 8-wire sensors
`are added to dynamically reference the voltage to cor-
`rect for this fluctuation during use (See Figure 2-2).
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 9
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`5-Wire Sensor
`2.5
`A 5-wire resistive touch sensor consists of a flex and
`stable layer, electrically separated by spacer dots. The
`touch position is determined by first applying a voltage
`gradient across the stable layer in the X-axis direction
`and using the flex layer to measure the axis touch posi-
`tion voltage. The second step is applying a voltage gra-
`dient across the stable layer in the Y-axis direction and
`using the flex layer to measure the axis touch position
`voltage.
`The voltage is not directly applied to the edges of the
`active layer, as it is for 4-wire and 8-wire sensors. The
`voltage is applied to the corners of a 5-wire sensor.
`
`FIGURE 2-3:
`
`5-Wire Decoding
`
`To measure the X-axis, the left edge of the layer is
`driven with 0V (ground), using connections to the upper
`left and lower left sensor corners. The right edge is
`driven with +5 VDC, using connections to the upper
`right and lower right sensor corners.
`To measure the Y-axis, the top edge of the layer is
`driven with 0V (ground), using connections to the upper
`left and upper right sensor corners. The bottom edge is
`driven with +5 VDC, using connections to the lower left
`and lower right sensor corners.
`The measured voltage at any position across a driven
`axis is predictable. A touch moving in the direction of
`the driven axis will yield a linearly changing voltage. A
`touch moving perpendicular to the driven axis will yield
`a relatively unchanging voltage (See Figure 2-3).
`
`DS41393B-page 10
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`3.0
`
`HARDWARE
`
`Main Schematic
`3.1
`A main application schematic for the SOIC/SSOP
`package pinout is shown in Figure 3-1.
`See Figure 1-2 for the QFN package pinout.
`
`FIGURE 3-1:
`
`MAIN SCHEMATIC (SOIC/SSOP PACKAGE PINOUT)
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 11
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`4, 5, 8-Wire Sensor Selection
`3.2
`The desired sensor type of 4/8-wire or 5-wire is
`hardware selectable using pin M2.
`
`TABLE 3-1:
`
`4/8-WIRE vs. 5-WIRE
`SELECTION
`
`Type
`
`M2 pin
`VSS
`4/8-wire
`5-wire
`VDD
`If 4/8-wire has been hardware-selected, then the
`choice of 4-wire or 8-wire is software-selectable via the
`TouchOptions Configuration register.
`When 4/8-wire is hardware-selected, the controller
`defaults to 4-wire operation. If 8-wire operation is
`desired, then the TouchOptions Configuration register
`must be changed.
`
`4-Wire Touch Sensor Interface
`3.3
`Sensor tail pinouts can vary by manufacturer and part
`number. Ensure that both sensor tail pins for one
`sensor axis (layer) are connected to the controller’s
`X-/X+ pins and the tail pins for the other sensor axis
`(layer) are connected to the controller’s Y-/Y+ pins. The
`controller’s X-/X+ and Y-/Y+ pin pairs do not need to
`connect to a specific sensor axis. The orientation of
`controller pins X- and X+ to the two sides of a given
`sensor axis is not important. Likewise, the orientation of
`controller pins Y- and Y+ to the two sides of the other
`sensor axis is not important.
`Connections to a 4-wire touch sensor are as follows
`(See Figure 3-2).
`
`FIGURE 3-2:
`
`4-WIRE TOUCH SENSOR INTERFACE
`
`Tie unused controller pins 5WSX-, SX+, SY-, and SY+
`to VSS.
`See Section 3.8 “ESD Considerations” and
`Section 3.9 “Noise Considerations” for important
`information regarding the capacitance of the controller
`schematic hardware.
`
`DS41393B-page 12
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`5-Wire Touch Sensor Interface
`3.4
`Sensor tail pinouts can vary by manufacturer and part
`number. Ensure sensor tail pins for one pair of
`diagonally related sensor corners are connected to the
`controller’s X-/X+ pins and the tail pins for the other pair
`of diagonally related corners are connected to the
`controller’s Y-/Y+ pins.
`The controller’s X-/X+ and Y-/Y+ pin pairs do not need
`to connect to a specific sensor axis. The orientation of
`controller pins X- and X+ to the two selected diagonal
`sensor corners is not important.
`Likewise, the orientation of controller pins Y- and Y+ to
`the other two selected diagonal sensor corners is not
`important. The sensor tail pin connected to its top layer
`must be connected to the controller’s 5WSX- pin.
`Connections to a 5-wire touch sensor are shown in
`Figure 3-3 below.
`
`FIGURE 3-3:
`
`5-WIRE TOUCH SENSOR INTERFACE
`
`Tie unused controller pins SX+, SY-, and SY+ to VSS.
`“Section 3.8 “ESD Considerations” and
`See
`Section 3.9 “Noise Considerations” for important
`information regarding the capacitance of the controller
`schematic hardware.
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 13
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`8-Wire Touch Sensor Interface
`3.5
`Sensor tail pinouts can vary by manufacturer and part
`number. Ensure both sensor tail pins for one sensor
`axis (layer) are connected to the controller’s X-/X+ pins
`and the tail pins for the other sensor axis (layer) are
`connected to the controller’s Y-/Y+ pins.
`The controller’s X-/X+ and Y-/Y+ pin pairs do not need
`to connect to a specific sensor axis. The orientation of
`controller pins X- and X+ to the two sides of a given
`sensor axis is not important. Likewise, the orientation of
`controller pins Y- and Y+ to the two sides of the other
`sensor axis is not important.
`The 8-wire sensor differs from a 4-wire sensor in that
`each edge of an 8-wire sensor has a secondary
`connection brought
`to
`the sensor’s
`tail. These
`secondary connections are referred to as “sense” lines.
`The controller pins associated with the sense line for an
`8-wire sensor contain an ‘S’ prefix in their respective
`names. For example, the SY- pin is the sense line
`connection associated with the main Y- pin connection.
`
`Consult with the sensor manufacturer’s specification to
`determine which member of each edge connected pair
`is the special 8-wire “sense” connection. Incorrectly
`connecting the sense and excite lines to the controller
`will adversely affect performance.
`The controller requires that the main and “sense” tail
`pin pairs for sensor edges be connected to controller
`pin pairs as follows:
`• Y- and SY-
`• Y+ and SY+
`• X- and 5WSX-
`• X+ and SX+
`Connections to a 8-wire touch sensor are shown in
`Figure 3-4 below.
`
`FIGURE 3-4:
`
`8-WIRE TOUCH SENSOR INTERFACE
`
`See Section 3.8 “ESD Considerations” and
`Section 3.9 “Noise Considerations” for important
`information regarding the capacitance of the controller
`schematic hardware.
`
`DS41393B-page 14
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`ESD Considerations
`3.8
`ESD protection is shown on the 4-wire, 5-wire, and
`8-wire interface applications schematics.
`The capacitance of alternate ESD diodes may
`adversely affect
`touch performance. A
`lower
`capacitance is better. The PESD5V0S1BA parts shown
`in the reference design have a typical capacitance of 35
`pF. Test to ensure that selected ESD protection does
`not degrade touch performance.
`ESD protection is shown in the reference design, but
`acceptable protection is dependent on your specific
`application. Ensure your ESD solution meets your
`design requirements.
`
`Noise Considerations
`3.9
`Touch sensor filtering capacitors are included in the
`reference design.
`
`Warning: Changing the value of the capacitors may
`adversely affect performance of the touch system.
`
`Status LED
`3.6
`The LED and associated resistor are optional.
`
`FIGURE 3-5:
`
`The LED serves as a status indicator that the controller
`is functioning. It will slow flash when the controller is
`running with no touch in progress. It will flicker quickly
`(mid-level on) when a touch is in progress.
`If the LED is used with SPI communication, then the
`LED will be off with no touch and flicker quickly
`(mid-level on) when a touch is in progress.
`Note:
`If the SIQ pin is not used, it must be left as
`a No Connect and NOT tied to circuit VDD or
`VSS.
`
` WAKE Pin
`3.7
`The AR1000’s WAKE pin is described as “Touch
`Wake-Up/Touch Detection”. It serves the following
`three roles in the controller’s functionality:
`• Wake-up from touch
`• Touch detection
`• Measure sensor capacitance
`The application circuit shows a 20 KΩ resistor
`connected between the WAKE pin and the X- pin on the
`controller chip. The resistor is required for product
`operation, based on all three of the above roles.
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 15
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`NOTES:
`
`DS41393B-page 16
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`I2CTM COMMUNICATIONS
`4.0
`The AR1021 is an I2C slave device with a 7-bit address
`of 0x4D, supporting up to 400 kHz bit rate.
`A master (host) device interfaces with the AR1021.
`I2C Hardware Interface
`4.1
`A summary of the hardware interface pins is shown
`below in Table 4-1.
`I2C HARDWARE INTERFACE
`TABLE 4-1:
`AR1021 Pin
`M1
`SCL
`SDA
`SDO
`
`Description
`Connect to VSS to select I2C™ communications
`Serial Clock to master I2C
`Serial Data to master I2C
`Data ready interrupt output to master
`
`M1 Pin
`• The M1 pin must be connected to VSS to config-
`ure the AR1021 for I2C communications.
`SCL Pin
`• The SCL (Serial Clock) pin is electrically
`open-drain and requires a pull-up resistor, typi-
`cally 2.2 K to 10 K, from SCL to VDD.
`• SCL Idle state is high.
`SDA Pin
`• The SDA (Serial Data) pin is electrically
`open-drain and requires a pull-up resistor, typi-
`cally 2.2K to 10K, from SDA to VDD.
`• SDA Idle state is high.
`• Master write data is latched in on SCL rising
`edges.
`• Master read data is latched out on SCL falling
`edges to ensure it is valid during the subsequent
`SCL high time.
`SDO Pin
`• The SDO pin is a driven output interrupt to the
`master.
`• SDO Idle state is low.
`• SDO will be asserted high when the AR1021 has
`data ready (touch report or command response)
`for the master to read.
`
` 2009-2012 Microchip Technology Inc.
`
`Preliminary
`
`DS41393B-page 17
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`4.2
`
`I2C Pin Voltage Level
`Characteristics
`I2C PIN VOLTAGE LEVEL CHARACTERISTICS
`TABLE 4-2:
`Function
`Pin
`Input
`VSS ≤ VIL≤ 0.2*VDD
`SCL/SCK
`SCL/SCK/TX
`0.8*VDD ≤ VIH ≤ VDD
`—
`
`SDO
`
`SDO
`
`Output
`
`—
`
`VSS ≤ VOL(1) ≤ (1.2V – 0.15*VDD)(2)
`(1.25*VDD – 2.25V)(3) ≤ VOH(1) ≤ VDD
`Open-drain
`
`SDA
`
`SDI/SDA/RX
`
`VSS ≤ VIL ≤ 0.2*VDD
`0.8*VDD ≤ VIH ≤ VDD
`Note 1: These parameters are characterized but not tested.
`2: At 10 mA.
`3: At –4 mA.
`
` Addressing
`4.3
`The AR1021’s device ID 7-bit address is: 0x4D
`(0b1001101)
`
`TABLE 4-3:
`
`A7
`1
`
`A6
`0
`
`I2C DEVICE ID ADDRESS
`Device ID Address, 7-bit
`A5
`A4
`A3
`0
`1
`1
`
`A2
`0
`
`A1
`1
`
`TABLE 4-4:
`
`I2C DEVICE WRITE ID
`ADDRESS
`A7 A6 A5 A4 A3 A2 A1 A0
`1
`0
`0
`1
`1
`0
`1
`0
`
`0x9A
`
`TABLE 4-5:
`
`I2C DEVICE READ ID
`ADDRESS
`A7 A6 A5 A4 A3 A2 A1 A0
`1
`0
`0
`1
`1
`0
`1
`1
`
`0x9B
`
`Master Read Bit Timing
`4.4
`Master read is to receive touch reports and command
`responses from the AR1021.
`• Address bits are latched into the AR1021 on the
`rising edges of SCL.
`• Data bits are latched out of the AR1021 on the
`rising edges of SCL.
`• ACK is presented (by AR1021 for address, by
`master for data) on the ninth clock.
`• The master must monitor the SCL pin prior to
`asserting another clock pulse, as the AR1021
`may be holding off the master by stretching the
`clock.
`
`FIGURE 4-1:
`
`I2C MASTER READ BIT TIMING DIAGRAM
`
`Steps
`1. SCL and SDA lines are Idle high.
`2. Master presents “Start” bit to the AR1021 by
`taking SDA high-to-low, followed by taking SCL
`high-to-low.
`3. Master presents 7-bit Address, followed by a
`R/W = 1 (Read mode) bit to the AR1021 on
`SDA, at the rising edge of eight master clock
`(SCL) cycles.
`
`4. AR1021 compares the received address to its
`device
`ID.
`If
`they match,
`the AR1021
`acknowledges (ACK) the master sent address
`by presenting a low on SDA, followed by a
`low-high-low on SCL.
`5. Master monitors SCL, as the AR1021 may be
`“clock stretching”, holding SCL low to indicate
`that the master should wait.
`
`DS41393B-page 18
`
`Preliminary
`
` 2009-2012 Microchip Technology Inc.
`
`

`
`AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
`
`7.
`
`6. Master receives eight data bits (MSb first)
`presented on SDA by the AR1021, at eight
`sequential master clock (SCL) cycles. The data
`is latched out on SCL falling edges to ensure it
`is valid during the subsequent SCL high time.
`If data transfer is not complete, then:
`- Master acknowledges (ACK) reception of the
`eight data bits by presenting a low on SDA,
`followed by a low-high-low on SCL.
`- Go to step 5.
`If data transfer is complete, then:
`- Master acknowledges (ACK) reception of the
`eight data bits and a completed data transfer
`by presenting a high on SDA, followed by a
`low-high-low on SCL.
`
`8.
`
`9. Master presents a “Stop” bit to the AR1021 by
`taking SCL low-high, followed by taking SDA
`low-to-high.
`
`Master Write Bit Timing
`4.5
`Master write is to send supported commands to the
`AR1021.
`• Address bits are latched into the AR1021 on the
`rising edges of SCL.
`• Data bits are latched into the AR1021 on the
`rising edges of SCL.
`• ACK is pres