LIS2HH12 datasheet(19/47 Pages) STMICROELECTRONICS

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DocID025344 Rev 5

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LIS2HH12

Digital main blocks

5.2

Data stabilization time / ODR change

The data stabilization time required when an ODR change is applied in order to have valid

usable data depends on the BW and ODR selected.

The table below provides the number of samples to be discarded in order to obtain valid

usable data.

5.3

FIFO

The LIS2HH12 embeds an acceleration data FIFO for each of the three output channels, X,

Y and Z. This allows consistent power saving for the system, since the host processor does

not need to continuously poll data from the sensor, but it can wake up only when needed

and burst the significant data out from the FIFO. This buffer can work according to the

following different modes: Bypass mode, FIFO-mode, Stream mode, Stream-to-FIFO mode,

Bypass-to-Stream, Bypass-to-FIFO. Each mode is selected by the FIFO_MODE bits in the

FIFO_CTRL (2Eh) register. Programmable FIFO threshold level, FIFO empty or FIFO

overrun events are available in the FIFO_CTRL (2Eh) register and can be set to generate

dedicated interrupts on the INT1 or INT2 pin.

FIFO_SRC (2Fh) (EMPTY) is equal to '1' when no samples are available.

FIFO_SRC (2Fh)(FTH) goes to '1' if new data arrives and FIFO_SRC (2Fh)(FSS [4:0]) is

greater than or equal to FIFO_CTRL (2Eh) (FTH [4:0]). FIFO_SRC (2Fh) (FTH) goes to '0' if

reading X, Y, Z data slot from FIFO and FIFO_SRC (2Fh) (FSS [4:0]) is less than or equal to

FIFO_CTRL (2Eh) (FTH [4:0]).

FIFO_SRC (2Fh) (OVR) is equal to '1' if a FIFO slot is overwritten.

The FIFO feature is enabled by writing the CTRL3 (22h) (FIFO_EN) bit to '1' in control

In order to guarantee the correct acquisition of data during the switching into and out of

FIFO mode, the first sample acquired must be discarded.

5.3.1

Bypass mode

In Bypass mode (FIFO_CTRL (2Eh) (FMODE [2:0])= 000), the FIFO is not operational and it

remains empty.

Bypass mode is also used to reset the FIFO when in FIFO mode.

Table 10. Number of samples to be discarded

ODR [Hz]

BW = 400 Hz

BW = 200 Hz

BW = 100 Hz

BW = 50 Hz

---

100

1111

200

1114

400

1147

800

14714

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