LSM6DS33 Datasheet, PDF (24/77 Pages) STMicroelectronics – iNEMO inertial module: always-on 3D accelerometer and 3D gyroscope

Functionality
LSM6DS33
5.4.1
5.4.2
5.4.3
Writing data in the FIFO can be configured to be triggered by the:
- accelerometer/gyroscope data-ready signal; in which case the ODR must be lower than or
equal to both the accelerometer and gyroscope ODRs;
- step detection signal.
In addition, each data can be stored at a decimated data rate compared to FIFO ODR and it
is configurable by the user, setting the registers FIFO_CTRL3 (08h) and FIFO_CTRL4
(09h). The available decimation factors are 2, 3, 4, 8, 16, 32.
Programmable FIFO threshold can be set in FIFO_CTRL1 (06h) and FIFO_CTRL2 (07h)
using the FTH [11:0] bits.
To monitor the FIFO status, dedicated registers (FIFO_STATUS1 (3Ah), FIFO_STATUS2
(3Bh), FIFO_STATUS3 (3Ch), FIFO_STATUS4 (3Dh)) can be read to detect FIFO overrun
events, FIFO full status, FIFO empty status, FIFO threshold status and the number of
unread samples stored in the FIFO. To generate dedicated interrupts on the INT1 and INT2
pads of these status events, the configuration can be set in INT1_CTRL (0Dh) and
INT2_CTRL (0Eh).
FIFO buffer can be configured according to five different modes:
– Bypass mode
– FIFO mode
– Continuous mode
– Continuous-to-FIFO mode
– Bypass-to-continuous mode
Each mode is selected by the FIFO_MODE_[2:0] in FIFO_CTRL5 (0Ah) register. To
guarantee the correct acquisition of data during the switching into and out of FIFO mode,
the first sample acquired must be discarded.
Bypass mode
In Bypass mode (FIFO_CTRL5 (0Ah) (FIFO_MODE_[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.
FIFO mode
In FIFO mode (FIFO_CTRL5 (0Ah) (FIFO_MODE_[2:0] = 001) data from the output
channels are stored in the FIFO until it is full.
To reset FIFO content, Bypass mode should be selected by writing FIFO_CTRL5 (0Ah)
(FIFO_MODE_[2:0]) to '000' After this reset command, it is possible to restart FIFO mode by
writing FIFO_CTRL5 (0Ah) (FIFO_MODE_[2:0]) to '001'.
FIFO buffer memorizes up to 4096 samples of 16 bits each but the depth of the FIFO can be
resized by setting the FTH [11:0] bits in FIFO_CTRL1 (06h) and FIFO_CTRL2 (07h). If the
STOP_ON_FTH bit in CTRL4_C (13h) is set to '1', FIFO depth is limited up to FTH [11:0]
bits in FIFO_CTRL1 (06h) and FIFO_CTRL2 (07h).
Continuous mode
Continuous mode (FIFO_CTRL5 (0Ah) (FIFO_MODE_[2:0] = 110) provides a continuous
FIFO update: as new data arrives, the older data is discarded.
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