ADXL375 Просмотр технического описания (PDF) - Analog Devices
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ADXL375 Datasheet PDF : 32 Pages
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Data Sheet
ADXL375
REGISTER DESCRIPTIONS
All registers in the ADXL375 are eight bits in length.
Register 0x00—DEVID (Read Only)
D7 D6 D5 D4 D3 D2 D1 D0
1
1
1
0
0
1
0
1
The read-only DEVID register holds the fixed device ID code
of 0xE5 (345 octal).
Register 0x1D—THRESH_SHOCK (Read/Write)
The THRESH_SHOCK register contains the unsigned threshold
value for shock interrupts. The magnitude of the shock event is
compared with the value in the THRESH_SHOCK register for
shock detection. The scale factor is 780 mg/LSB. A value of 0 may
result in undesirable behavior if single shock/double shock inter-
rupts are enabled.
Register 0x1E, Register 0x1F, Register 0x20—OFSX,
OFSY, OFSZ (Read/Write)
The OFSX, OFSY, and OFSZ registers contain user-configured
offset adjustments in twos complement format with a scale factor
of 1.56 g/LSB. The value stored in the offset registers is automat-
ically added to the acceleration data, and the resulting value is
stored in the output data registers (Address 0x32 to Address 0x37).
For more information about offset calibration and the use of the
offset registers, see the Offset Calibration section.
Register 0x21—DUR (Read/Write)
The DUR register contains an unsigned time value representing
the maximum time that an event must be above the THRESH_
SHOCK threshold to qualify as a shock event. The scale factor
is 625 μs/LSB. A value of 0 disables the single shock and double
shock functions.
Register 0x22—Latent (Read/Write)
The latent register contains an unsigned time value representing
the wait time from the detection of a shock event to the start of
the time window (specified by the window register) during which
a possible second shock event can be detected. The scale factor
is 1.25 ms/LSB. A value of 0 disables the double shock function.
Register 0x23—Window (Read/Write)
The window register contains an unsigned time value repre-
senting the amount of time after the expiration of the latency
time (specified by the latent register) during which a second
valid shock can begin. The scale factor is 1.25 ms/LSB. A value
of 0 disables the double shock function.
Register 0x24—THRESH_ACT (Read/Write)
The THRESH_ACT register contains the unsigned threshold
value for detecting activity. The magnitude of the activity event
is compared with the value in the THRESH_ACT register. The
scale factor is 780 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 contains the unsigned threshold
value for detecting inactivity. The magnitude of the inactivity
event is compared with the value in the THRESH_INACT
register. The scale factor is 780 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 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 detected. The scale factor is 1 sec/LSB. Unlike the other
interrupt functions, which use unfiltered output data (see the
Threshold Detection and Bandwidth section), the inactivity
function uses filtered output data.
At least one output sample must be generated for the inactivity
interrupt to be triggered. For this reason, the inactivity function
may appear to be 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. The maximum
value for TIME_INACT is 255 sec.
Register 0x27—ACT_INACT_CTL (Read/Write)
D7
D6
D5
D4
ACT AC/DC ACT_X enable ACT_Y enable ACT_Z enable
D3
D2
D1
D0
INACT AC/DC INACT_X enable INACT_Y enable INACT_Z enable
The ACT_INACT_CTL register selects dc-coupled or ac-coupled
operation and selects the axes that participate in activity and
inactivity detection.
ACT AC/DC and INACT AC/DC Bits
A setting of 0 for the ACT AC/DC and INACT AC/DC bits
selects dc-coupled operation; a setting of 1 selects ac-coupled
operation. In dc-coupled operation, the current acceleration
magnitude is compared directly with the values in the THRESH_
ACT and THRESH_INACT registers 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 data are then compared to this ref-
erence value and, if the magnitude of the difference exceeds the
THRESH_ACT value, an activity interrupt is triggered.
Similarly, in ac-coupled operation for inactivity detection, a refer-
ence 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 the
THRESH_INACT value. If the difference is less than the value
in the THRESH_INACT register for the time specified in the
TIME_INACT register, the device is considered inactive, and
the inactivity interrupt is triggered.
Rev. 0 | Page 21 of 32
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