ADXL346ACCZ-R2 datasheet(24/40 Pages) AD

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ADXL346

Data Sheet

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’ed,

causing the activity function to trigger when any of the partici-

pating axes exceeds the threshold. For inactivity detection, all

participating axes are logically AND’ed, causing the inactivity

function to trigger only if all participating axes are below the

threshold for the specified period of time.

The THRESH_FF register is eight bits and holds the threshold

value, in unsigned format, for free-fall detection. The acceleration

on all axes is compared with the value in THRESH_FF to deter-

mine if a free-fall event occurred. The scale factor is 62.5 mg/LSB.

Note that a value of 0 mg may result in undesirable behavior if

the free-fall interrupt is enabled. Values between 300 mg and

600 mg (0x05 to 0x09) are recommended.

The TIME_FF register is eight bits and stores an unsigned time

value representing the minimum time that the value of all axes

must be less than THRESH_FF to generate a free-fall interrupt.

The scale factor is 5 ms/LSB. A value of 0 may result in undesirable

behavior if the free-fall interrupt is enabled. Values between 100 ms

and 350 ms (0x14 to 0x46) are recommended.

Improved

tap

Suppress

TAP_X

enable

TAP_Y

enable

TAP_Z

enable

Improved Tap Bit

The improved tap bit is used to enable improved tap detection.

This mode of operation improves tap detection by performing

an ac-coupled differential comparison of the output acceleration

data. The improved tap detection is performed on the same output

data available in the DATAX, DATAY, and DATAZ registers. Due

to the dependency on the output data rate and the ac-coupled

differential measurement, the threshold and timing values for

single taps and double taps must be adjusted for improved tap

detection. For further explanation of improved tap detection, see

the Improved Tap Detection section. Improved tap is enabled

by setting the improved tap bit to a value of 1 and is disabled

by clearing the bit to a value of 0.

Suppress Bit

Setting the suppress bit suppresses double-tap detection if

acceleration greater than the value in THRESH_TAP is present

between taps. See the Tap Detection section for more details.

TAP_x Enable Bits

A setting of 1 in the TAP_X enable, TAP_Y enable, or TAP_Z

enable bit enables x-, y-, or z-axis participation in tap detection.

A setting of 0 excludes the selected axis from participation in

tap detection.

ACT_X

source

ACT_Y

source

ACT_Z

source

Asleep

TAP_X

source

TAP_Y

source

TAP_Z

source

ACT_x Source and TAP_x Source Bits

These bits indicate the first axis involved in a tap or activity

event. A setting of 1 corresponds to involvement in the event,

and a setting of 0 corresponds to no involvement. When new

data is available, these bits are not cleared but are overwritten by

the new data. The ACT_TAP_STATUS register should be read

before clearing the interrupt. Disabling an axis from participation

clears the corresponding source bit when the next activity or

single-tap/double-tap event occurs.

Asleep Bit

A setting of 1 in the asleep bit indicates that the part is asleep,

and a setting of 0 indicates that the part is not asleep. This bit

toggles only if the device is configured for autosleep. See the

information on autosleep mode.

LOW_POWER

Rate

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 is

associated with somewhat higher noise (see the Power Modes

section for details).

Rate Bits

These bits select the device bandwidth and output data rate (see

Table 7 and Table 8 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 communication protocol and

frequency selected. Selecting too high of an output data rate with a

low communication speed results in samples being discarded.

Link

AUTO_SLEEP

Measure

Sleep

Wakeup

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,

the inactivity and activity functions are concurrent. Additional

information can be found in the Link Mode section.

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