I am able to setup the chip for tap or tap-tap detection, but I found there was serious false trigger issue (simply by shaking the unit will cause the chip to generate tap or tap-tap event).
Here is the register configuration I am using:
- ODR=200Hz (chip work in low power mode)
- LNOISE=1 reduced noise mode enabled (0x2A)
- PULSE_HPF_BYP=0; PULSE_LPF_EN=0 (0x0F)
- HPF cutoff freq.=2Hz (0x0F)
- DPA=1, ELE=1 & pulses detection for Z axis only (0x21)
- PULSE_THSZ=1.5g (0X25)
- PULSE_TMLT=25ms (0X26)
- PULSE_LTCY=125ms (0X27)
- PULSE WIND=150ms (0X28)
In addition, I observed that:
When LNOISE=1, it is very easy for the false trigger to happen even when PULSE_THSZ is set to 6.36g (the spec. mentioned the dynamic range will be reduced to 4g).
When LNOISE=0, it is very easy for the false trigger to happen even when PULSE_THSZ is set to 7.938g.
It seems to me that the PULSE_THSZ factor in the pulse detection algorithm is not working correctly.
I appreciate if someone could help to solve the problem or give any suggestion.