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PDF LM8300 Data sheet ( Hoja de datos )
| Número de pieza | LM8300 | |
| Descripción | Four Wire Resistive Touchscreen Controller with Brownout | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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PRELIMINARY
October 2002
LM8300/LM8400/LM8500
Four Wire Resistive Touchscreen Controller with
Brownout
General Description
The LM8300/8400/8500 is a 4-wire resistive touch screen
controller. The controller samples and drives the touch
screen without the need of any external hardware. The built
in 10-bit A/D provides a maximum of 500 coordinate pairs
per second (cpps). The data sampled from the touch screen
is sent out on the UART at a speed of 38400 bps.
The controller has a power-saving mode which causes the
controller to self-power down when no touch is detected on
the touch screen for a specified amount of time. In the
self-power down mode, the current drawn is typically less
than 2 µA. The device resumes normal operation when a
touch is detected on the touch screen or communication is
detected on the UART. In addition to the self-power down
mode, the controller can be disabled by pulling the SHUT-
DOWN pin low. The controller resumes normal operation
when the SHUTDOWN pin is tristated or pulled high.
The controller has an internal non-volatile memory storage
element to store configuration data such as calibration points
or controller configurations.
Devices included in this datasheet:
Operating
Device
Voltage
Brownout
Voltage
LM8300
3, 5 V
2.7 to 2.9 V
Operating
Frequency
3.27 MHz
I/O
Pins
18
LM8400
3, 5 V No Brownout
3.27 MHz
18
LM8500
5V
4.17V to 4.5V 3.27, 10 MHz
18
Packages
44 LLP, 44 PLCC,
48 TSSOP
44 LLP, 44 PLCC,
48 TSSOP
44 LLP, 44 PLCC,
48 TSSOP
Temperature
0˚C to +70˚C
0˚C to +70˚C
0˚C to +70˚C
Features
KEY FEATURES
n Supports 4 wire resistive touch panels
n Low power standby current typically less than 2 µA at
5.5V
n Maximum speed of 500 coordinate pairs per second
n Automatic wake up and return to standby
n 10 bit A/D
n On-chip touch screen current drivers - no external driver
required
n UART interface
n Controller configurations are stored in the internal
non-volatile storage element
n Touch pressure can be measured
APPLICATIONS
n Personal Digital Assistants
n Smart Hand-Held Devices
n Touch Screen Monitors
n Point-of-Sales Terminals
n KIOSK
n Pagers
n Cell Phones
COP8™ is a trademark of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation DS200372
www.national.com
1 page  
2.0 Pin Descriptions
Pin Name
RESET
DTR
WD_OUT
CLK_SET1
Unused2
Unused2
Unused2
Unused2
OSC_OUT
OSC_IN
Unused2
Unused2
UART_TX
UART_RX
SHUTDOWN
Unused2
Unused2
WAKE-UP
X+
Y-
X-
Y+
Unused2
Unused2
FILTER_OUT
FILTER_IN
GND
AGND
AVCC
VCC
Unused2
Unused2
Unused2
Unused2
Unused2
Unused2
Unused2
Direction
I
I
O
I
O
I
O
I
I
I
I/O
I/O
I/O
I/O
O
I
Pinouts for 44- and 48-Pin Packages
Pin Description
Reset pin, pull low to reset
UART Data terminal ready signal, low
if not ready
Watchdog output, tie to RESET pin
for correct function
Used to set if crystal is 3.3 MHz (low)
or 10 MHz (floating or pulled high)
Clock oscillator output
Clock oscillator input
UART transmit pin (inverted for use
with standard RS-232 drivers)
UART receive pin (inverted for use
with standard RS-232 drivers
Shutdown pin, puts the device in halt
mode if pulled low
Used to wake up the processor from
halt mode with touch on touch screen
Drives the X+ wire, also analog input
when sampling
Drives the Y- wire, also analog input
when sampling
Drives the X- wire, also analog input
when sampling
Drives the Y+ wire, also analog input
when sampling
Analog output to the filter
Analog input from the filter
Digital ground
Analog ground
Analog power supply, connect to filter
for best performance
Digital power supply
44-Pin LLP
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
X
X
36
37
38
39
40
44-Pin PLCC 48-Pin TSSOP
11
22
33
44
55
66
77
88
99
10 10
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
20 20
21 21
22 22
23 23
24 24
25 25
26 26
27 27
28 28
29 31
30 32
X 33
X 34
31 35
32 36
33 37
34 38
35 39
5 www.national.com
5 Page 
4.0 Functional Description (Continued)
$B2: Read software version number
Reply Byte #1: $C7 (Software version number)
Byte #2: First byte in version number, year 20 (00-99)
Byte #3: Second byte in version number, month (1-12)
Byte #4: Third byte in version number, day (1-31)
$B3: Read # of calibration points
Reply Byte #1: $CA (Acknowledge)
Byte #2: ($00 — no calibration done, $02 — 2 points,
$05 — 5 points or $0D — 13 points)
$B4: Read stored calibration points
Reply Byte #1: $CA (Acknowledge)
Byte #2: ($00 — no calibration done, $02 — 2 points,
$05 — 5 points or $0D — 13 points)
Byte #3: X-max (2 MSB for coordinate 1)
Byte #4: X-min (8 LSB for coordinate 1)
Byte #5: Y-max (2 MSB for coordinate 1)
Byte #6: Y-min (8 LSB for coordinate 1)
Continue until all coordinates have been sent. A zero is send
back if calibration has not been performed and there are no
data bytes.
$B8: Set focus value
Byte #2: Focus value (0-63)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Focus value (0-63)
The set focus command allows the setting of different values
to improve touch screen focusing. Focusing is defined as the
ability of the touch screen controller to detect exactly identi-
cal coordinate values from measurement to measurement if
the pointer on the touch screen has not moved. The focus
values are equivalent to pixels of touch screen resolution. If
for example a value of 2 is selected, this means that every
coordinate value that is within two pixels of the previously
measured coordinate value is considered to be identical to
that previous value and that in this case the touch screen
controller transmits the previous coordinate information. This
keeps the mouse pointer steady at the point being touched,
rather than "jumping around" the point. A Focus value of zero
disables the focusing algorithm. The default setting is 4.
$BA: Set number of samples per coordinate
Byte #2: Number of samples per coordinate ($01 - 1
samples/coordinate, $02 - 2 samples/coordinate, $04
- 4 samples/coordinate, $08 - 8 samples/coordinate,
$10 - 16 samples/coordinate, $20 - 32
samples/coordinate)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Number of samples per coordinate ($01 - 1
samples/coordinate, $02 - 2 samples/coordinate, $04
- 4 samples/coordinate, $08 - 8 samples/coordinate,
$10 - 16 samples/coordinate, $20 - 32
samples/coordinate)
This command allows the selection of different sample num-
bers per X, Y, and Z coordinates. The higher the number of
samples per X, Y, and Z coordinates, the better the accuracy,
but the lower the coordinates per second data rate. The
default setting is 8.
$BB: Set communication mode
Byte #2: Communication mode ($01 = stream, $02 =
touchdown, $04 = liftoff)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Communication mode ($01 = stream, $02 =
touchdown, $04 = liftoff)
See the communication modes section for a description of
the stream, touchdown and liftoff modes. This command
selects the communication mode. The default setting is
stream mode.
$BC: Set max delta
Byte #2: Max delta value (0-63)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Max delta value (0-63)
See the averaging algorithms section for a detailed descrip-
tion of this setting. Simply put, this command sets how much
the "coordinate velocity" can change from one coordinate to
the next. The default setting is 8.
$BD: Set calibration points
Byte #2: High nibble: Number of calibration points
($01 = two, $02 = five, $04 = thirteen)
Low nibble: Active calibration cross (1-13 = cross #)
Reply Byte #1: $CA (Acknowledge)
Byte #2: High nibble: Number of calibration points
($01=two, $02=five, $04=thirtheen)
Low nibble: Active calibration cross # (1-13)
Refer to the calibration section for details.
$BE: Set minimum pressure
Byte #2: Minimum pressure value (0-127)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Minimum pressure value (0-127)
This setting controls how high the pressure (Z-axis) must be
in order for samples to be accepted. Setting this value too
low may result in having faulty coordinates accepted. This
value is internally multiplied by two in the controller (due to
the 7-bit limitation in the communication format, which can
not send 8-bit values larger than 127 in one byte). The
default setting is 40.
$A0: Toggle disable/enable external filter path
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
This command enable/disable external filter path. The exter-
nal filter path enabled option will require the addition of a
single external low pass filter (either R/C or active OpAmp
based), which is then applied to the touch screen signal
lines. This option can be used in high noise environments to
significantly improve performance and accuracy of the touch
screen controller.
The default setting is filter path enabled.
$A2: Toggle disable/enable self-power down
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
This command can switch between self-power down mode
enable or disabled. Refer to the Power Save Mode section
for details. The default setting is Self-Power Down mode
enabled. If the echo mode is enabled, any command byte
send to the device will be echo back and executed.
$A3: Toggle disable/enable echo mode
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
The echo mode is available for debugging purposes. If en-
abled, the touch screen controller will echo back any data
that is received via the UART interface.
11 www.national.com
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LM8300.PDF ] | |
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