EVAL-ADXL312Z Analog Devices, EVAL-ADXL312Z Datasheet - Page 21

• Manufacturer Part Number: EVAL-ADXL312Z
• Description: Daughter Cards & OEM Boards EB Digital Output Three-Axis Accel
• Manufacturer: Analog Devices
• Series: ADXL312r

Specifications of EVAL-ADXL312Z

• Rohs: yes
• Product: Evaluation Boards
• Description/function: 3 axis accelerometer evaluation board
• Interface Type: I2C, SPI
• Maximum Operating Temperature: + 105 C
• Minimum Operating Temperature: - 40 C
• Operating Supply Voltage: 2 V to 3.6 V
• Factory Pack Quantity: 1
• For Use With: ADXL312

REGISTER DEFINITIONS
Register 0x00—DEVID (Read Only)
D7
1
The DEVID register holds a fixed device ID code of 0xE5.
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 11.6 mg/LSB (that is, 0x7F = +1.5 g). The
value stored in the offset registers is automatically added to the
acceleration data, and the resulting value is stored in the output
data registers.
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;
therefore, the magnitude of the activity event is compared with
the value in the THRESH_ACT register. The scale factor is
46.4 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;
therefore, the magnitude of the inactivity event is compared
with the value in the THRESH_INACT register. The scale factor is
46.4 mg/LSB. A value of 0 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
D6
1
D6
ACT_X enable
D2
INACT_X enable
D5
1
D4
0
D5
ACT_Y enable
D1
INACT_Y enable
D3
0
D2
1
D4
ACT_Z enable
D0
INACT_Z enable
D1
0
D0
1
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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 acceleration
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. For activity detection, all participating axes are
logically OR’ e d, causing the activity function to trigger when
any of the participating axes exceeds the threshold. For inactiv-
ity detection, all participating axes are logically AND’ e d, causing
the inactivity function to trigger only if all participating axes are
below the threshold for the specified period of time.
Register 0x2C—BW_RATE (Read/Write)
D7
0
LOW_POWER Bit
A setting of 0 in the LOW_POWER bit selects normal operation,
and a setting of 1 selects reduced power operation, which has
somewhat higher noise (see the Power Modes section for details).
Rate Bits
These bits select the device bandwidth and output data rate (see
Table 6 and Table 7 for details). The default value is 0x0A, which
translates to a 100 Hz output data rate. An output data rate
should be selected that is appropriate for the communica-tion
protocol and frequency selected. Selecting too high of an output
data rate with a low communication speed results in samples
being discarded.
Register 0x2D—POWER_CTL (Read/Write)
D7
0
Link Bit
A setting of 1 in the link bit with both the activity and inactivity
functions enabled delays the start of the activity function until
inactivity is detected. After activity is detected, inactivity detection
begins, preventing the detection of activity. This bit serially links
the activity and inactivity functions. When this bit is set to 0,
D6
0
D6
0
D5
Link
D5
0
D4
AUTO_SLEEP
D4
LOW_POWER
D3
Measure
D3
D2
D2
Sleep
Rate
ADXL312
D1
D1
Wakeup
D0
D0