ST LPS22HB - Table 2: FIFO Mode Selection

AN4672
Use case and configuration example for the
LPS22HB
DocID027655 Rev 3
19/24
 Resolution
 Current consumption
 FIFO Mode Output Data Rate
 Low Pass Filter
In The register RES_CONF (0x1Ah), the LC_EN bit allows to select two possible
configurations: Low Noise Mode (default) or Low Current Mode.
The configuration can be modified for adapting the output resolution and the power
consumption of the sensor to the design specifications.In the first case the resolution is
higher than resolution in Low Current mode. Conversely the low current mode is suggested
for applications in which the power consumption has to be low at disadvantage of the
output resolution.
In addition, to further improving the power saving, the embedded 32-slot of 40-bit data
FIFO, to store the pressure and temperature output values, can be utilized by setting the
FIFO mode. 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
seven different modes as described in table 1. The FIFO buffer is enabled when the
FIFO_EN bit in CTRL_REG2 (11h) is set to '1' and each mode is selected by the
FIFO_MODE[2:0] bits in FIFO_CTRL (14h). Programmable FIFO threshold status, FIFO
overrun events and the number of unread samples stored are available in the
FIFO_STATUS (26h)register and can be set to generate dedicated interrupts on the
INT_DRDY pad using the CTRL_REG3 (12h) register.
Table 2: FIFO mode selection
F_MODE2
F_MODE1
FMODE0
FIFO mode selection
0
0
0
Bypass mode
0
0
1
FIFO mode
0
1
0
Stream mode
0
1
1
Stream to FIFO mode
1
0
0
Bypass to Stream mode
1
0
1
Reserved
1
1
0
Dynamic stream mode
1
1
1
Bypass to FIFO mode
As far as the ODR setting is concerned, ranging in active mode among 1,10,25,50, 75 Hz,
it has to be defined looking at the target power consumption, and the appropriate data
output refresh time. Finally, a low pass filter on pressure data can be enabled by setting the
EN_LPFP bit in CTRL_REG1 (10h) with two possible selectable cutoff ODR/9 and ODR/20
(bit LPF_CFG of CTRL_REG1). Keep in mind that in order to modify CTRL_REG1 register
the procedure described in figure 15 has to be used.