LPS25H datasheet(12/45 Pages) STMICROELECTRONICS

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Functionality

LPS25H

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DocID023722 Rev 5

The FIFO buffer is enabled by setting to 1 the FIFO_EN bit (21h - CTRL_REG2) and can

work accordingly to 4 different modes: bypass mode, FIFO mode, Stream mode and FIFO

Mean mode. Each mode is selected by the FIFO_MODE bits in FIFO_CTRL (2Eh).

Programmable Watermark level WTM_POINT4:0 (FIFO_CTRL register, 2Eh),

EMPTY_FIFO or FULL_FIFO events can be enabled to generate dedicated interrupts on

the INT1 pin (configuration through CTRL3 (22h) and CTRL4 (23h)).

3.4.1

Bypass mode (F_MODE2:0=”000” in FIFO_CTRL (2Eh))

The FIFO is not operational and for this reason it remains empty.

3.4.2

FIFO mode (F_MODE2:0=”001” in FIFO_CTRL (2Eh))

The data from PRESS_OUT_XL (28h), PRESS_OUT_L (29h) and PRESS_OUT_H (2Ah)

are stored in the FIFO.

A Watermark interrupt can be enabled (WTM_EN bit in CTRL2 (21h) in order to be raised

when the FIFO is filled to the level specified in the WTM_POINT4:0 bits of FIFO_CTRL

(2Eh). The FIFO continues filling until it is full (32 slots of data for XL, L and H). When full,

the FIFO stops collecting data from the input pressure data.

3.4.3

Stream mode (F_MODE2:0=”010” in FIFO_CTRL (2Eh))

The data from PRESS_OUT_XL (28h), PRESS_OUT_L (29h) and PRESS_OUT_H (2Ah)

measurements are stored in the FIFO. The FIFO continues filling until it’s full (32 slots of

data for XL, L and H). When full, the FIFO discards the older data as the new arrive. A

Watermark interrupt can be enabled and set as in FIFO mode.

Stream mode is use to implement the digital filter averaging the samples stored in the FIFO

3.4.4

FIFO mean mode (F_MODE2:0=”110” in FIFO_CTRL (2Eh))

The pressure data are not directly sent to the output register but are firstly stored in the

FIFO to calculate the average. The FIFO Mean Mode can be enabled by setting the

FIFO_MEAN_DEC bit (CTRL_REG2, 21h). The number of averaged samples can be set by

changing the watermark in WTM_POINT4:0 bits of FIFO_CTRL (2Eh).

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