Data Sheet
ADXL36±
When the accelerometer is in wake-up mode, the TIME_ACT
value is ignored and activity is detected based on a single
acceleration sample.
ACTIVITY THRESHOLD REGISTERS
To detect activity, the ADXL362 compares the absolute value of
the 12-bit (signed) acceleration data with the 11-bit (unsigned)
THRESH_ACT value. See the Motion Detection section for
more information on activity detection.
The term, THRESH_ACT, refers to an 11-bit unsigned value com-
prising the THRESH_ACT_L register, which holds its eight LSBs;
and the THRESH_ACT_H register, which holds its three MSBs.
INACTIVITY THRESHOLD REGISTERS
To detect inactivity, the absolute value of the 12-bit acceleration
data is compared with the 11-bit (unsigned) THRESH_INACT
value. See the Motion Detection section for more information.
THRESH_ACT is set in codes; the value in g depends on the
measurement range setting that is selected.
The term, THRESH_INACT, refers to an 11-bit unsigned value
comprised of the THRESH_INACT_L registers, which holds its
eight LSBs and the THRESH_INACT_H register, which holds
its three MSBs.
THRESH_ACT [g] = THRESH_ACT [codes]/Sensitivity
[codes per g]
Address: 0x20, Reset: 0x00, Name: THRESH_ACT_L
This 11-bit unsigned value sets the threshold for inactivity
detection. This value is set in codes; the value (in g) depends on
the measurement range setting selected:
Address: 0x21, Reset: 0x00, Name: THRESH_ACT_H
THRESH_INACT [g] =
THRESH_INACT [codes]/Sensitivity [codes per g]
Address: 0x23, Reset: 0x00, Name: THRESH_INACT_L
ACTIVITY TIME REGISTER
Address: 0x22, Reset: 0x00, Name: TIME_ACT
Address: 0x24, Reset: 0x00, Name: THRESH_INACT_H
The activity timer implements a robust activity detection that
minimizes false positive motion triggers. When the timer is
used, only sustained motion can trigger activity detection. Refer
to the Fewer False Positives section for additional information.
The value in this register sets the number of consecutive
samples that must have at least one axis greater than the activity
threshold (set by THRESH_ACT) for an activity event to be
detected.
INACTIVITY TIME REGISTERS
The 16-bit value in these registers sets the number of consecu-
tive samples that must have all axes lower than the inactivity
threshold (set by THRESH_INACT) for an inactivity event to
be detected.
The time (in seconds) is given by the following equation:
Time = TIME_ACT/ODR
The TIME_INACT_L register holds the eight LSBs and the
TIME_INACT_H register holds the eight MSBs of the 16-bit
TIME_INACT value.
where:
TIME_ACT is the value set in this register.
ODR is the output data rate set in the FILTER_CTL register
(Address 0x2C).
The time in seconds can be calculated as
Time = TIME_INACT/ODR
Setting the activity time to 0x00 has the same result as setting
this time to 0x01: Activity is detected when a single acceleration
sample has at least one axis greater than the activity threshold
(THRESH_ACT).
where:
TIME_INACT is the 16-bit value set by the TIME_INACT_L reg-
ister (eight LSBs) and the TIME_INACT_H register (eight MSBs).
ODR is the output data rate set in the FILTER_CTL register
(Address 0x2C).
Rev. B | Page 27 of 44
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