LIS3DH and fall detection

[martech]

Posted on November 12, 2013 at 04:12

I have used the LIS3DH for movement and angle detection for about 18 months. I now wish to use it for fall detection. Previously I ued another brand where you setup a register and get an interrupt when a zero G occurs in all axes for a certain time. I can see no way to do this with the LIS3DH but it advertises that it can be done. I can do it ''manually'' by continually reading each axis and setting a timer to record when it is continuously like this for, say 100mS. Is there an easier way that uses less power?

Thanks

[gavrilov]

Posted on November 12, 2013 at 04:51

Hello Peter.

May be ''Application Note'' AN3308 is help you?

CD00290365.pdf: AN3308, 6.3 Free-fall and wake-up interrupts:

The LIS3DH interrupts signal can behave as free-fall and wake-up. (and so on...)

[Thiago REIS]

Posted on November 18, 2013 at 14:24

Hello Peter and Gav,

In order to support your free fall application development I have attached an image showing a suggestion for the registers setup of the LIS3DH for a free fall interrupt in low power mode.

I have also attached the LIS3DH datasheet where you will be able to find a better description of each register.

Thank you very much,

Thiago Reis

________________

Attachments :

LIS3DH_FREE-FALL.PNG : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzKD&d=%2Fa%2F0X0000000bKD%2FNMbOBN.L9xyAL5MAg_jKSF2AVHKZ7VfkUbRJLaebc.U&asPdf=false

LIS3DH.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzL5&d=%2Fa%2F0X0000000bKF%2FK7hzlEqd6e8MgzzRWeCvKFMgD3KPwHpnd.0ponF5f7o&asPdf=false

[manbir]

Posted on December 29, 2014 at 13:27

It appears that some of the registers in the attached image from Thiago Reis (e.g. INT2_CFG, INT2_THS) are not defined in the datasheet.   Also, I'm not able to see an interrupt when executing the sequence in paragh. 6.3.3 of AN3308 (Wakeup with HPF).  I was not able to find the address of the register  HP_FILTER_RESET mentioned in step # 8, since this register is also missing from the datasheet.  Could there be an updated version of the datasheet that I may have missed?  It would be great if someone at ST could send a working sequence for the wake-up usecase with HPF turned on.

Thanks,

[argo777]

Posted on March 29, 2016 at 12:29

Confirm some registers aeems to be marked as reserved with a threatening note stating not to modify them or damage will happen.

Is this some kind of mistake?

Stefano