how to enable or disable free fall detection on LIS2DH12TR sensor? how to validate whether the interrupt is generated by free fall detection?

[Mnago.1]

can you please provide the inputs ASAP, currently this task is at highest priority.

[Eleon BORLINI]

Hi @Mnago.1​ ,

>> how to enable or disable free fall detection on LIS2DH12TR sensor?

You can check the application note AN5005 at p.26, where the free-fall configuration for the LIS2DH12 is described.

The pseudo-code for this embedded feature is the following one:

1. Write 57h into CTRL_REG1 // Turn on the sensor, enable X, Y, and Z, ODR = 100 Hz
2. Write 00h into CTRL_REG2 // High-pass filter disabled
3. Write 40h into CTRL_REG3 // Interrupt activity 1 driven to INT1 pad
4. Write 00h into CTRL_REG4 // FS = ±2 g
5. Write 08h into CTRL_REG5 // Interrupt 1 pin latched
6. Write 16h into INT1_THS // Set free-fall threshold = 350 mg
7. Write 03h into INT1_DURATION // Set minimum event duration
8. Write 95h into INT1_CFG // Configure free-fall recognition
9. Poll INT1 pad; if INT1 = 0 then go to 10 // Poll INT1 pin waiting for the free-fall event
10. (Free-fall event has occurred; insert your code here) // Event handling
11. Read INT1_SRC register // Clear interrupt request
12. Go to 9
//If you want to disable the free-fall recognition, write 00h into INT1_CFG

>> how to validate whether the interrupt is generated by free fall detection?

The INT1_CFG configuration is set so that for each axis (X, Y, Z) the cross of the threshold(s) in the high-to-low direction is activated and the 3 interrupts are combined in logic OR. An event that causes such a behavior is almost always a fall event.

If you are interested in a C code implementation for this embedded feature, although it is for another (similar) product, the LIS2DW12, you can check the C driver on Github here (lis2dw12_free_fall.c).

-Eleon