ScreenCoder
TM
UR7HCTS2-U860
High-Performance USB
Touch Screen Controller / Digitizer
HID & SYSTEM MANAGEMENT PRODUCTS, MOUSECODER
TM
FAMILY
DESCRIPTION
The ScreenCoder
TM
USB IC is the
first single IC that seamlessly
interfaces ANY 4- or 8-wire
resistive touch screen to a USB-
equipped system. It is also the
first touch screen controller IC on
the market designed to
accommodate a very wide range of
size, capacitance and resistance of
4- or 8-wire touch screens,
providing a universal performance
solution among different OEM
products and touch screen
vendors. This unique feature of the
IC provides OEMs with a wide
variety of interchangeable touch
screen options.
Unlike digitizers, the
ScreenCoder
TM
USB integrates a
digitizer with a controller that
performs all touch detection, noise
filtering, error elimination and
provides the host with processed
and stable positioning data over
USB. Semtech’s unique motion
algorithms provide high resistance
to RF and other noise sources
resulting in precise, non-jittery
cursor control.
Ideal application for the
ScreenCoder
TM
USB include
portable devices, interactive kiosks
and industrial / custom displays
with integrated touch screens.
The universal features of the
ScreenCoder
TM
USB, as
implemented in both the system
and the sensor interface, reduce
the development effort and cost of
touch input based systems. The
ScreenCoder
TM
USB is available in
a slim, 36-pin SSOP package.
FEATURES
• Controller & digitizer in a single IC
• Interfaces the system via USB
• Works with ANY 4- or 8-wire
resistive touch screen regardless
of size, material or vendor
• Provides high resolution - 1000
points per axis, enabling IC to
make precise drawing and
signature captures
• Accurate, quick touch response
due to Semtech’s advanced
sampling technology and
algorithms
APPLICATIONS
• Handhelds/Notebooks
• Portable Devices
PIN ASSIGNMENTS
• Interactive Kiosks
• Industrial/Custom Touch Screens
• Highly resistant to RF and other
noise
• No digitizer or external A/D
necessary
• Fully compliant with USB HID
specifications; works with native
USB drivers including Windows®
98, Me and 2000
• Convienent calibration applet
offered free of charge
• Uses slim 36-pin, SSOP package
• Customized versions available
1
RSVD1
RSVD2
RSVD3
SXL
SYT
SYB
SXR
RSVD4
RSVD5
RSVD6
RSVD7
VREF
_RESET
VSS2
VDD
OSCIN
_OSCOUT
VSS
18
36
36-pin SSOP
D+
D-
_RB
RSVD13
XR2
YB2
YT2
XL2
RSVD12
RSVD11
USBV
RSVD10
RSVD9
RSVD8
XL1
YT1
YB1
XR1
19
ScreenCoder, MouseCoder are trademarks of
Semtech Corp. All other trademarks belong to
their respective companies.
Copyright Semtech 2000-2001
DOC7-TS2-U860-DS-101
1
www.semtech.com
ORDERING CODE
Package Options
36-pin, Plastic SSOP
Pitch in mm’s
0.8mm
TA=-20° C to +85° C
UR7HCTS2-U860-DR
Other Materials
ScreenCoder
TM
USB Eval Kit
Type
Evaluation Kit
Order number
EVK7-TS2-U860-XXX
BLOCK DIAGRAM FOR THE UR7HCTS2-U860
Right Button
Power
Management
Section
Switch Interface
Power -On Reset
Drivers for Touch
Screen
Touch Panel
Interface
4
Sense Lines
4
16-Bit Timer
Sensor Interface
Oscillator Circuit
USB
Communication
Interface
D+
D-
OSCIN
_OSCOUT
Copyright Semtech 2000-2001
DOC7-TS2-U860-DS-101
2
www.semtech.com
FUNCTIONAL DESCRIPTION
The UR7HCTS2-U860 consists
functionally of five major sections
(see the Functional Diagram on
Page 2). These are the Sensor
Interface, the Power Management
Section, the 16-Bit Timer, the
Oscillator Circuit and the USB
Interface.
OSCILLATOR
This IC has a built-in Oscillator
circuit capable of operations with
an external 6.00 MHz Clock source,
or a Ceramic Resonator (preferably
with built-in Load Capacitors) or a
Crystal with external Load
Capacitors.
POWER MANAGEMENT
According to the USB specification,
if there is no activity of the USB port
for 3 ms, the system is considered
to be in a suspended state. The
ScreenCoder
TM
USB IC, on
detecting that the system is in
suspend, will check the state of the
touch screen and the right button.
If there is no touch pressure
detected or no button pressed, the
ScreenCoder
TM
USB enters into the
suspended state. In suspend the
IC fully complies with the USB
specification for the power
consumption, dissipating current
only in the USB-mandated pull-up
for the device identification.
Another technique the IC uses to
conserve power is called remote
wake-up. If the system relies on the
device to perform wake-up, the IC
will send a resume message to the
system when there is activity on the
touch screen or button.
PIN DEFINITIONS
Mnemonic Pin #
Power:
VDD
15
VSS
14,18
3.3V
22
_Reset
13
Oscillators:
OSCI
16
OSCO
17
USB:
D-
35
D+
36
Touch
Screen:
XR1, XR2
19,32
YB1, YB2
31,20
YT1, YT2
21,30
XL1, XL2
22,29
SXR
7
SYB
6
SYT
5
SXL
4
VREF
12
SOUT
23
_RB
34
RDVD1-13
1-3,8-11
23-25,
27-28
33
Type
P
P
P
Name and Function
Power Supply
Ground
USB Reference Voltage Out
I
I
O
I/O
I/O
Reset
Oscillator Input
Oscillator Output
USB D- Line
USB D+ Line
I/O
I/O
I/O
I/O
Al
Al
Al
Al
Al
O
I
I/O
Touch Screen Right Drive Pins
Touch Screen Bottom Drive Pins
Touch Screen Top Drive Pins
Touch Screen Left Drive Pins
Touch Screen Sense Pin:
for X Right
Touch Screen Sense Pin:
for Y Bottom
Touch Screen Sense Pin:
for Y Top
Touch Screen Sense Pin:
for X Left
Voltage Reference for A/D Converter
Output control data to A/D Converter
Mouse Right Button
Reserved for future use
Note:
An underscore before a pin mnemonic denotes an active low signal.
Pin Types Legend:
I=Input; O=Output; I/O=Input or Output; P=Power; Al= Analog Input
POWER MANAGEMENT (CON’T)
If the system does not allow remote wake-up, the ScreenCoder
TM
USB will
not send resume messages to the system when it is awoken by activity on
the touch screen or button.
Copyright Semtech 2000-2001
DOC7-TS2-U860-DS-101
3
www.semtech.com
TOUCH SCREEN SENSOR INTERFACE
The ScreenCoder
TM
USB can acquire data from any 4- or 8-wire resistive touch screen sensors. The sensor
interface has the following features:
Touch detection
The IC periodically checks touch pressure applied to the panel. If there is no touch, the IC will not perform
measurements and will not send data to system. When touch pressure is detected, the IC further qualifies and
determines the amount of pressure. Semtech’s proprietary, patent-pending touch detection algorithm performs this
test very quickly, accommodating sensors with various plate-to-plate capacitances.
Touch Measurement
Position information is only collected if it has been determined that the touch pressure is sufficient for an accurate
reading. To obtain position information from the Resistive Touch Screen Sensor, the ScreenCoder
TM
USB uses four
internal drivers (two pins for each driver) and four sense lines. During sampling, the drivers of the X-axis are
activated by setting one X-drive high and the other X-drive low. The drivers for Y-axis are set floating. This action
produces a voltage gradient across the touch screen's surface in the X direction. The internal A/D measures both
the voltage across the activated X-plane and the voltage potential between the planes. Next, the drivers for the Y-
axis are activated while the drivers for X-axis are set floating. Again, the internal A/D measures both voltage across
the activated plane and potential between the planes. The X and Y absolute position is obtained from these four
A/D measurements. The IC keeps measuring the touch pressure even while the positioning data is acquired. If
insufficient touch pressure is detected during sampling of the position, the current data set will be rejected.
Touch algorithm
Due to vibration and electrical noise, the raw data can not be used directly. Internal data processing delivers
consistent position accuracy and quick touch response.
Resolution
The ScreenCoder
TM
USB uses a built-in A/D converter to get the touch position. The maximum touch screen
resolution is 1000 points per direction. Resolution varies somewhat for different touch screen sensors, due to
voltage droop on connecting wires.
Touch screen from different makers
Operating parameters for the touch screens from different manufacturers vary depending on the size of the sensor,
material it is made from, and mechanical construction. The ScreenCoder
TM
USB takes these properties into
account, and adjusts automatically for plate-to-plate capacitance, intrinsic plate resistances, etc.
Buttons
The ScreenCoder
TM
USB implements both left and right buttons, however, there is no physical left button. Left
button press is reported when there is touch pressure on the panel. The left button is released when there is no
pressure on the panel. The right button is a physical button, and can be used individually.
Copyright Semtech 2000-2001
DOC7-TS2-U860-DS-101
4
www.semtech.com
USB FUNCTIONALITY
The ScreenCoder
TM
USB is a low-
speed USB device with remote
wake-up capability. The IC asks
the system to send report requests
every 10ms according to USB
specification for low speed device.
The ScreenCoder
TM
USB describes
itself as a pointer, and provides
absolute position data to the
system.
USB DESCRIPTORS
Offset
Part
Size
Value
Description
Device Descriptor
0
bLength
1
bDescriptonType
1
1
0x12
0x01
0x0100
0x00
0x00
0x00
0x08
0x047A
0x0004
0x0061
0x04
0x0E
0x00
0x01
2
3
4
5
6
8
10
12
14
15
16
17
bcdUSB
bDeviceClass
bDeviceSubClass
bDeviceProtocol
bMaxPacketSize0
idVendor
idProduct
bcdDevice
iManufacture
iProduct
iSerialNumber
bNum-
2
1
1
1
1
2
2
2
1
1
1
1
Numeric expression specifying the size of
device descriptor
Device descriptor type
USB HID spec release number 01.00
Class code
Sub class code
Protocol code
Maximum packet size for EP0
USAR's vendor ID
USAR ScreenCoder
TM
USB Product ID
Device release number
Index of string descriptor describing
manufacturer
Index of string descriptor describing
product
Index of String descriptor describing
serial number
Number of possible configurations
Configuration Descriptor
0
bLength
1
1
bDescriptorType
1
2
wTotalLength
2
4
bNumInterface
1
5
6
7
8
bConfigurationValue1
iConfiguration
1
bmAttribute
1
MaxPower
1
0x09
0x02
0x0022
0x01
0x01
0x00
0xA0
0x32
Size of configuration descriptor in bytes
Configuration (assigned by USB)
Total length of data returned for this
Number of interfaces supported by this
configuration
Current configuration value
Configuration string descriptor index
Configuration characteristics - bus
powered, with remote wakeup
Maximum power consumption of USB
device 100 mA
Interface Descriptor
0
bLength
1
1
bDescriptorType
1
2
bInterfaceNumber 1
3
bAlternateSetting 1
4
bNumEndpoints
1
5
bInterfaceClass
1
6
bInterfaceSubClass 1
7
8
bInterfaceProtocol 1
iInterface
1
0x09
0x04
0x00
0x00
0x01
0x03
0x00
0x02
0x00
Size of Interface descriptor in bytes
Interface descriptor type
Number of interface
Number of alternate setting
Number of endpoint
Class code (HID)
Subclass code (nor boot interface
subclass)
Protocol code = mouse
Index of string descriptor describing this
interface
HID Descriptor
0
bLength
1
bDescriptorType
2
bcdHID
4
bCountryCode
5
bNumDescriptor
6
bDescriptorType
7
wDescriptorLength
1
1
2
1
1
1
2
0x09
0x21
0x0100
0x00
0x01
0x22
0x0038
Size of HID descriptor in byte
HID descriptor type
HID Spec release number
Hardware target country
Number of HID class descriptor follow
Report descriptor type
Total length of report descriptor
Copyright Semtech 2000-2001
DOC7-TS2-U860-DS-101
5
www.semtech.com
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