DocID025978 Rev 1
19/26
AN4450
Using FIFO modes
26
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
2
7 Hz
8
1 Hz
7
