LM8300IMT9/NOPB National Semiconductor, LM8300IMT9/NOPB Datasheet - Page 11

• Manufacturer Part Number: LM8300IMT9/NOPB
• Manufacturer: National Semiconductor

Specifications of LM8300IMT9/NOPB

• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Package Type: TSSOP
• Mounting: Surface Mount
• Pin Count: 48
• Lead Free Status / RoHS Status: Compliant

9.0 Functional Description
This command allows the user to read all the selected pa-
rameters. It is primary intended to aid in debugging. This
command can also be used if a configuration utility needs to
determine the current setting of controller.
$B2: Read software version number
$B3: Read # of calibration points
$B4: Read stored calibration points
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
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 #11: Number of calibration coordinates (0, 2, 5 or
13)
Byte #12: Toggle-flags:
1=enabled)
1=enabled)
1=enabled)
Byte #13: Pressure threshold for valid touch
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)
Reply Byte #1: $CA (Acknowledge)
Byte #2: ($00 — no calibration done, $02 — 2 points,
$05 — 5 points or $0D — 13 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)
Byte #2: Focus value (0-63)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Focus value (0-63)
Byte #2: Number of samples per coordinate ($01 - 1
samples/coordinate, $02 - 2 samples/coordinate, $04
Bit #5: calibration coordinates check (0=disabled,
Bit
Bit #3: Echo mode (0=disabled, 1=enabled)
Bit #2: Self Power-Down mode (0=disabled,
Bit #1: Unused
Bit #0: External filter path (0=disabled, 1=enabled)
#4:
Pressure
measurement
(Continued)
(0=disabled,
11
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
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
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
Refer to the calibration section for details.
$BE: Set minimum pressure
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
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
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
samples/coordinate)
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)
Byte #2: Max delta value (0-63)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Max delta value (0-63)
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
- 4 samples/coordinate, $08 - 8 samples/coordinate,
$10
samples/coordinate)
Byte #2: Minimum pressure value (0-127)
Reply Byte #1: $CA (Acknowledge)
Byte #2: Minimum pressure value (0-127)
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)
-
-
16
16
samples/coordinate,
samples/coordinate,
$20
$20
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