LPS27HHW datasheet(41/60 Pages) STMICROELECTRONICS

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LPS27HHW

Figure 25. “Threshold-based” interrupt event

To enable the AUTOZERO mode, the AUTOZERO bit must be set to '1' and then the

measured pressure value is used as the reference and stored in the register REF_P

(REF_P_L (15h), REF_P_H (16h)). From this point on, the output pressure value

(PRESS_OUT_XL (28h), PRESS_OUT_L (29h), PRESS_OUT_H (2Ah)) is updated with

the difference between the measured pressure and REF_P.

–

P_DIFF_IN = measured pressure - REF_P

–

PRESS_OUT = measured pressure - REF_P

After the first conversion, the AUTOZERO bit is automatically set back to '0'. In order to

return back to normal mode, the RESET_AZ bit in the INTERRUPT_CFG (0Bh) register has

to be set to '1'. This also resets the content of the REF_P registers to 0.

AUTOREFP mode allows using the pressure differential for the generation of the interrupt

keeping the output pressure registers PRESS_OUT (PRESS_OUT_XL (28h),

PRESS_OUT_L (29h), PRESS_OUT_H (2Ah)) without comparing REF_P. If the

AUTOREFP bit is set to '1', the measured output pressure is used as the reference in the

–

P_DIFF_IN = measured pressure - REF_P

The output registers PRESS_OUT (28h, 29h and 2Ah) are not changed by REF_P and

shows as follows.

–

PRESS_OUT = measured pressure

After the first conversion, the AUTOREFP bit is automatically set to '0'. In order to return

back to normal mode, the RESET_ARP bit has to be set to '1'

LPS27HHW Arkusz danych(PDF) 41 Page - STMicroelectronics