LSM6DB0 Datasheet, PDF (26/66 Pages) STMicroelectronics – 3D accelerometer, 3D gyroscope and signal processor

Accelerometer and gyroscope functionality
LSM6DB0
7.2.1
FIFO_SRC (2Fh) (FTH) goes to '1' when the number of unread samples (FIFO_SRC (2Fh)
(FSS5:0)) is greater than or equal to FTH [4:0] in FIFO_CTRL (2Eh). If FIFO_CTRL (2Eh)
(FTH[4:0]) is equal to 0, FIFO_SRC (2Fh) (FTH) goes to ‘0’.
FIFO_SRC (2Fh) (OVRN) is equal to '1' if a FIFO slot is overwritten.
FIFO_SRC (2Fh) (FSS [5:0]) contains stored data levels of unread samples. When FSS
[5:0] is equal to ‘000000’, FIFO is empty, when FSS [5:0] is equal to ‘100000’, FIFO is full
and the unread samples are 32.
The FIFO feature is enabled by writing '1' in CTRL_REG9 (23h) (FIFO_EN).
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_CTRL (2Eh)(FMODE [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.
As described in Figure 9, for each channel only the first address is used. When a new data
is available the old data is overwritten.
x_i,y_i,z_i
empty
Figure 9. Bypass mode
x₀
y₀
z₀
x₁
y₁
z₁
x₂
y₂
z₂
x₃₁
y₃₁
z₃₁
7.2.2
FIFO mode
In FIFO mode (FIFO_CTRL (2Eh) (FMODE [2:0] = 001) data from the output channels are
stored in the FIFO until it is overwritten.
To reset FIFO content, Bypass mode should be selected by writing FIFO_CTRL (2Eh)
(FMODE [2:0]) to '000'. After this reset command, it is possible to restart FIFO mode, writing
FIFO_CTRL (2Eh) (FMODE [2:0]) to '001'.
The FIFO buffer memorizes 32 levels of data but the depth of the FIFO can be resized by
setting the STOP_ON_FTH bit in CTRL_REG9 (23h). If the STOP_ON_FTH bit is set to '1',
FIFO depth is limited to FIFO_CTRL (2Eh)(FTH [4:0]) + 1 data.
A FIFO threshold interrupt can be enabled (INT_OVR bit in INT1_CTRL (0Ch) ) in order to
be raised when the FIFO is filled to the level specified by the FTH[4:0] bits of FIFO_CTRL
(2Eh). When a FIFO threshold interrupt occurs, the first data has been overwritten and the
FIFO stops collecting data from the input channels.
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