EVAL-ADXL350Z Analog Devices, EVAL-ADXL350Z Datasheet - Page 24

• Manufacturer Part Number: EVAL-ADXL350Z
• Description: Acceleration Sensor Development Tools EB
• Manufacturer: Analog Devices

Specifications of EVAL-ADXL350Z

• Rohs: yes
• Interface Type: I2C, SPI
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Product: Evaluation Boards
• Factory Pack Quantity: 1

ADXL350
REGISTER DEFINITIONS
Register 0x00—DEVID (Read Only)
D7
1
The DEVID register holds a fixed device ID code of 0xE5
(345 octal).
Register 0x1D—THRESH_TAP (Read/Write)
The THRESH_TAP register is eight bits and holds the threshold
value for tap interrupts. The data format is unsigned, so the
magnitude of the tap event is compared with the value in
THRESH_TAP. The scale factor is 31.2 mg/LSB (that is, 0xFF
= +8 g). A value of 0 may result in undesirable behavior if tap/
double tap interrupts are enabled.
Register 0x1E, Register 0x1F, Register 0x20—OFSX,
OFSY, OFSZ (Read/Write)
The OFSX, OFSY, and OFSZ registers are each eight bits and
offer user-set offset adjustments in twos complement format
with a scale factor of 7.8 mg/LSB (that is, 0x7F = +1 g).
Register 0x21—DUR (Read/Write)
The DUR register is eight bits and contains an unsigned time
value representing the maximum time that an event must be
above the THRESH_TAP threshold to qualify as a tap event. The
scale factor is 625 µs/LSB. A value of 0 disables the tap/double
tap functions.
Register 0x22—Latent (Read/Write)
The latent register is eight bits and contains an unsigned time
value representing the wait time from the detection of a tap event
to the start of the time window (defined by the window register)
during which a possible second tap event can be detected. The scale
factor is 1.25 ms/LSB. A value of 0 disables the double tap function.
Register 0x23—Window (Read/Write)
The window register is eight bits and contains an unsigned time
value representing the amount of time after the expiration of the
latency time (determined by the latent register) during which a
second valid tap can begin. The scale factor is 1.25 ms/LSB. A
value of 0 disables the double tap function.
Register 0x24—THRESH_ACT (Read/Write)
The THRESH_ACT register is eight bits and holds the threshold
value for detecting activity. The data format is unsigned, so the
magnitude of the activity event is compared with the value in
the THRESH_ACT register. The scale factor is 31.2 mg/LSB.
A value of 0 may result in undesirable behavior if the activity
interrupt is enabled.
Register 0x25—THRESH_INACT (Read/Write)
The THRESH_INACT register is eight bits and holds the threshold
value for detecting inactivity. The data format is unsigned, so
the magnitude of the inactivity event is compared with the value
in the THRESH_INACT register. The scale factor is 31.2 mg/LSB.
D6
1
D5
1
D4
0
D3
0
D2
1
D1
0
D0
1
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A value of 0 mg may result in undesirable behavior if the inactivity
interrupt is enabled.
Register 0x26—TIME_INACT (Read/Write)
The TIME_INACT register is eight bits and contains an unsigned
time value representing the amount of time that acceleration
must be less than the value in the THRESH_INACT register for
inactivity to be declared. The scale factor is 1 sec/LSB. Unlike
the other interrupt functions, which use unfiltered data (see the
Threshold section), the inactivity function uses filtered output
data. At least one output sample must be generated for the
inactivity interrupt to be triggered. This results in the function
appearing unresponsive if the TIME_INACT register is set to a
value less than the time constant of the output data rate. A value
of 0 results in an interrupt when the output data is less than the
value in the THRESH_INACT register.
Register 0x27—ACT_INACT_CTL (Read/Write)
D7
ACT ac/dc
D3
INACT ac/dc
ACT AC/DC and INACT AC/DC Bits
A setting of 0 selects dc-coupled operation, and a setting of
1 enables ac-coupled operation. In dc-coupled operation, the
current acceleration magnitude is compared directly with
THRESH_ACT and THRESH_INACT to determine whether
activity or inactivity is detected.
In ac-coupled operation for activity detection, the acceleration
value at the start of activity detection is taken as a reference
value. New samples of acceleration are then compared to this
reference value, and if the magnitude of the difference exceeds
the THRESH_ACT value, the device triggers an activity
interrupt.
Similarly, in ac-coupled operation for inactivity detection, a
reference value is used for comparison and is updated whenever
the device exceeds the inactivity threshold. After the reference
value is selected, the device compares the magnitude of the
difference between the reference value and the current accel-
eration with THRESH_INACT. If the difference is less than the
value in THRESH_INACT for the time in TIME_INACT, the
device is considered inactive and the inactivity interrupt is
triggered.
ACT_x Enable Bits and INACT_x Enable Bits
A setting of 1 enables x-, y-, or z-axis participation in detecting
activity or inactivity. A setting of 0 excludes the selected axis from
participation. If all axes are excluded, the function is disabled.
Register 0x28—THRESH_FF (Read/Write)
The THRESH_FF register is eight bits and holds the threshold
value, in unsigned format, for free-fall detection. The root-sum-
square (RSS) value of all axes is calculated and compared with
the value in THRESH_FF to determine if a free-fall event occurred.
The scale factor is 31.2 mg/LSB. Note that a value of 0 mg may
D6
ACT_X enable
D2
INACT_X enable
D5
ACT_Y enable
D1
INACT_Y enable
Data Sheet
D4
ACT_Z enable
D0
INACT_Z enable