DocID025978 Rev 1

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AN4450

Using FIFO modes

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While the speed of new averaged output is the one defined by ODR[2..0] in register

CTRL_REG1 (0x20).

In case 2, the number of samples is not selected by WTM_POINT[4..0] but is automatically

set from ODR value.

It is important to note that FIFO Mean mode with decimated output is not possible for

ODR=1 (data rate at 1 Hz).

As soon as FIFO Mean mode is set, the buffer is cleaned.

5.1.6

Hardware digital filter

To achieve the final averaging, an HW digital filter is used.

Table 3. Number of averaged samples vs WTM_POINT setting

WTM_POINT[4..0]

Number of averaged samples

00001

2

00011

4

00111

8

01111

16

11111

32

25Hz

for ODR=4

12.5Hz

for ODR=3

7Hz

for ODR=2

1Hz

for ODR=1

Table 4. ODR setting in FIFO Mean mode decimated

ODR[2..0]

Data rate from

sensor

Number of samples

Output data rate

Data ready every

samples

4

25 Hz

32

1 Hz

25

3

12.5 Hz

16

1 Hz

12

27 Hz

81 Hz

7