LIS2DTW12 FIFO threshold interrupt not correct

[RStra]

Hello,

I'm using a LIS2DTW12, here the configuration :

• ODR 400Hz
• FIFO threshold on INT2 push pull interrupt.
• Threshold 16
• Continuous mode

All seems to work correctly but sometimes I have an incorrect interrupt. The INT2 signal is yellow, the purple is a GPIO of my micro toggled when there is an ISR rising edge on INT2 is detected. The picture (1) show an unusual toggle (on the micro ISR) and on the code I read first 16 samples from the FIFO and then after a second interrupt just 6 samples (no overrun flag). In the other picture 2 and 3 the zoom of the problem, the yellow signal goes down for some uS then it goes up again so the micro see a new fifo threshold interrupt. Now why the INT2 goes down and the up again even if the FIFO hasn't reach the threshold ?

 

Regards,

Riccardo