ILPS22QSTR datasheet(34/57 Pages) STMICROELECTRONICS

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Figure 22. “Threshold-based” interrupt event

P_DIFF_IN

Negative

Threshold positive value

Threshold negative value

Positive

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 (16h), REF_P_H (17h)). 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.

9.2

THS_P_L (0Ch)

User-defined threshold value for pressure interrupt event (Least significant bits) (R/W)

THS7

THS6

THS5

THS4

THS3

THS2

THS1

THS0

THS[7:0]

This register contains the low part of threshold value for pressure interrupt generation.

Default value: 00h

The threshold value for pressure interrupt generation is a 15-bit unsigned right-justified value composed of

THS_P_H (0Dh) and THS_P_L (0Ch).The value is expressed as:

THS_P (15-bit unsigned) = desired interrupt threshold (hPa) x 16 for full-scale mode 1 (up to 1260 hPa,

FS_MODE bit set to 0 in CTRL_REG2 (11h))

THS_P (15-bit unsigned) = desired interrupt threshold (hPa) x 8 for full-scale mode 2 (up to 4060 hPa, FS_MODE

bit set to 1 in CTRL_REG2 (11h)

To enable the interrupt event based on this user-defined threshold, the PHE bit or PLE bit (or both bits) in

INTERRUPT_CFG (0Bh) has to be enabled.

ILPS22QS

THS_P_L (0Ch)

DS13431 - Rev 3

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