LIS2DUXS12 datasheet(13/104 Pages) STMICROELECTRONICS

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3.2.4

Activity/inactivity, Android stationary/motion detection functions

The activity/inactivity function recognizes the device’s sleep state and allows reducing system power

consumption.

When the activity/inactivity function is activated by setting the SLEEP_ON bit in WAKE_UP_THS (1Ch), the

device automatically goes to the inactivity output data rate selected by the INACT_ODR[1:0] bits in register

CTRL4 (13h).

With this feature the system may be efficiently switched from low-power mode to full performance depending on

user-selectable positioning and acceleration events, thus ensuring power saving and flexibility.

The Android stationary/motion detection function only recognizes the device’s sleep state.

When the Android stationary/motion detection function is activated by setting to a stationary condition the

INACT_ODR[1:0] bits in register CTRL4 (13h), the device detects acceleration below a fixed threshold but does

not change the ODR after sleep state detection.

The activity/inactivity recognition and Android stationary/motion detection functions are activated by writing the

desired threshold in the WAKE_UP_THS (1Ch) register. The high-pass filter is automatically enabled.

If the device is in sleep (inactivity/stationary) mode, when at least one of the axes exceeds the threshold in

WAKE_UP_THS (1Ch), the device goes into a sleep-to-wake state (as wake-up).

For the activity/inactivity function, the device, in a wake-up state, returns to the ODR before sleep state detection.

Activity/inactivity, Android stationary/motion detection threshold and duration can be configured in the following

control registers:

WAKE_UP_THS (1Ch)

WAKE_UP_DUR (1Dh)

3.2.5

Interrupt event recognition

The device may be configured to generate interrupt signals coming from an independent inertial wake-up/free-fall

event or from the position of the device itself. Thresholds and timing of this interrupt generator are programmable

by the end user in runtime.

Automatic programmable sleep-to-wake-up and return-to-sleep functions are also available for enhanced power

saving.

The device interrupts signal can behave as:

•

Free-fall: 3-axis underthreshold recognition;

•

Wake-up: axis recognition;

•

Wake-to-sleep: change of state recognition active-sleep (also known as activity-inactivity);

•

6D and 4D orientation detection: change of position recognition;

•

Tap-tap: single, double, triple axis and sign recognition.

All these functions are parallel but during sleep it is not possible to recognize a tap-tap event. All these signals

can be driven to the two interrupt pins (INT1 and INT2) through registers MD1_CFG (1Fh) and MD2_CFG (20h).

All these functions are enabled by setting the INTERRUPTS_ENABLE bit in register INTERRUPT_CFG (17h) to

It is possible to configure the duration of the interrupt using the LIR bit in INTERRUPT_CFG (17h) as shown in the

following table.

Table 9. Configuration of duration of interrupt

LIR

Interrupt type

Level mode

Latched mode

•

Interrupt level mode: the interrupt signal goes high when an interrupt event occurs and is reset when the

acceleration data fall below the threshold.

•

Interrupt latched mode: the interrupt signal on the INT1/INT2 pins is the OR of the interrupt flags enabled

through the MD1_CFG (1Fh) and MD2_CFG (20h) registers. Each interrupt flag goes to 1 when an

interrupt event occurs and is reset when the dedicated source register is read. The interrupt generator

block is inhibited 1 ODR after the reset event. It is possible to reset all the interrupt flags simultaneously by

reading the ALL_INT_SRC (24h) register.

LIS2DUXS12

Functionality

DS14035 - Rev 2

page 13/104

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