LIS2HH12 datasheet(18/47 Pages) STMICROELECTRONICS

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LIS2HH12

18/47

DocID025344 Rev 5

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5.1

Activity/Inactivity function

The Activity/Inactivity recognition function allows reducing the power consumption of the

system in order to develop new smart applications.

When the Activity/Inactivity recognition function is activated, the LIS2HH12 is able to

automatically go to 10Hz sampling rate and to wake up as soon as the interrupt event has

been detected, increasing the output data rate and bandwidth.

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 Activity/Inactivity recognition function is activated by writing the desired threshold in the

ACT_THS (1Eh) register. The high-pass filter is automatically enabled.

When the acceleration falls below the threshold for a duration of at least (8 ACT_DUR

+1)/ODR, the CTRL1 (20h) (ODR [2:0]) bits of CTRL1 are bypassed (Inactivity) and

internally set to 10Hz (ODR [2:0] = 001), but the content of the CTRL1 (20h) (ODR [2:0]) bits

are left untouched.

When the acceleration exceeds the threshold (ACT_THS (1Eh)), the ODR setting in CTRL1

(20h) is restored immediately (Activity).

Once the Activity/Inactivity detection function is enabled, the status can be brought out on

INT1 by setting the CTRL3 (22h) (INT1_INACT) bit to 1.

To disable the Activity/Inactivity detection function, set the content of the ACT_THS (1Eh)

Table 9. Activity/Inactivity function control registers

LSB value

ACT_THS

Full scale / 128 [mg]

ACT_DUR

8/ODR [s]

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