LIS2DH12 Activity / Inactivity recognition

[MZadn.1]

According to datasheet and AN5005, LIS2DH12 accelerometer can go to sleep & wake up + generate I2_ACT interrupt when acceleration goes below / above the threshold defined in ACT_THS.

Which acceleration exactly is taken into account for this strategy? Maximum / minimum of X,Y,Z? Resultant? Is gravity compensated for or not?

[Federica Bossi]

Hi @Community member​ ,

Welcome to ST Community!

As you can see in fig 8 of AN5005, when you use wake up if one axis is above the defined threshold you have the I2_ACT interrupt.
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[MZadn.1]

Hi Federica,

If I got it right, figure 8 applies to the free-fall and wake-up configuration of INTx interrupt that is set up by writing to INTx_CFG, INTx_THS and INTx_DURATION registers.

My question was about another functionality that is configured by writing to ACT_THS (0x3Eh) and ACT_DUR (0x3Fh) registers:

 

Which acceleration is considered above, underlined in red? There is no such register for this functionality, as there are INT1_CFG and INT2_CFG for free-fall and wake up-interrupts, which allow the AND / OR combination of some / all axes to be specified. So how are the 3 axes combined together here to make the device switch between "Sleep-to-wake" and "Return-to-sleep"?

[Federica Bossi]

Hi @Community member​ ,

This functionality also works the same way. The three axis are in OR so if one axis is above the threshold you have the switch.

[MZadn.1]

The three axis are in OR

This was the information I was missing. Thank you.