LPS25H Datasheet, PDF (38/45 Pages) STMicroelectronics – Embedded temperature compensation

FIFO operating details
8
FIFO operating details
LPS25H
8.1
FIFO registers
This device embeds a 32-slot x 24 bit FIFO pressure data coming from the PRESS_OUT
(@ 28..2Ah). It allows lower frequency of serial bus transactions and provides more time to
collect all taken measurements. The FIFO can operate in the following modes:
The mode is defined by 3 bits @0x2E: FIFO_CTRL. F_MODE[2:0]
BYPASS MODE [000]
In this mode the FIFO is disabled and stays empty. Pressure is ready directly.
FIFO MODE [001]
All pressure measurement are filling the FIFO. The FIFO content is read by reading the
PRESS_OUT registers @28..2Ah). A watermark interrupt can be enabled (CTRL2.
WTM_EN) which is raised when the FIFO is filled to the level specified in FIFO_CTRL.
WTM_POINT[4:0]. When the FIFO is full, the FIFO stops collecting incoming pressure
measurements.
BYPASS TO STREAM MODE [100]
The FIFO is in BYPASS mode till the trigger event. Then the STREAM MODE starts
FIFO MEAN Mode [110] & FIFO_mean_dec = 0
In this mode, the FIFO is used in STREAM mode and its content can be averaged by HW.
The hardware calculated running (moving) average can be read in PRESS_OUT registers
at anytime. This is used to further reduce the pressure noise at low power.
The number of samples to average is selectable through WTM_POINT[4:0]. See Table 22.
Table 22. Running average sample size
WTM_POINT[4:0]
Sample averaged
00001
00011
00111
01111
11111
others
2
4
8
16
32
Reserved
38/45
BYPASS to FIFO mode [111]
The FIFO switch from BYPASS to FIFO mode when the event is asserted
Accessing the FIFO data:
FIFO data is read through PRESS_OUT registers. When FIFO is in Stream, Trigger or FIFO
mode, a read operation to the PRESS_OUT registers provide the data stored in the FIFO.
Each time data is read from the FIFO, the oldest entry is placed in the PRESS_OUT
registers and both single read and burst read operation can be used.
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