ADXL362BCCZ-R2 datasheet(27/44 Pages) AD

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Data Sheet

ADXL362

Rev. B | Page 27 of 44

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.

THRESH_ACT is set in codes; the value in g depends on the

measurement range setting that is selected.

THRESH_ACT [g] = THRESH_ACT [codes]/Sensitivity

[codes per g]

Address: 0x20, Reset: 0x00, Name: THRESH_ACT_L

Address: 0x21, Reset: 0x00, Name: THRESH_ACT_H

ACTIVITY TIME REGISTER

Address: 0x22, Reset: 0x00, Name: TIME_ACT

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.

The time (in seconds) is given by the following equation:

Time = TIME_ACT/ODR

where:

TIME_ACT is the value set in this register.

ODR is the output data rate set in the FILTER_CTL register

(Address 0x2C).

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).

When the accelerometer is in wake-up mode, the TIME_ACT

value is ignored and activity is detected based on a single

acceleration sample.

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.

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.

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:

THRESH_INACT [g] =

THRESH_INACT [codes]/Sensitivity [codes per g]

Address: 0x23, Reset: 0x00, Name: THRESH_INACT_L

Address: 0x24, Reset: 0x00, Name: THRESH_INACT_H

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_INACT_L register holds the eight LSBs and the

TIME_INACT_H register holds the eight MSBs of the 16-bit

TIME_INACT value.

The time in seconds can be calculated as

Time = TIME_INACT/ODR

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).

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