LSM6DSTX datasheet(40/175 Pages) STMICROELECTRONICS

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6.6.6

Bypass-to-FIFO mode

In bypass-to-FIFO mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 111), data measurement storage inside FIFO

operates in FIFO mode when selected triggers are equal to 1, otherwise FIFO content is reset (bypass mode).

FIFO behavior changes according to the trigger event detected in one of the following interrupt events:

•

Single tap

•

Double tap

•

Wake-up

•

Free-fall

•

D6D

6.6.7

FIFO reading procedure

The data stored in FIFO are accessible from dedicated registers and each FIFO word is composed of 7

bytes: one tag byte (FIFO_DATA_OUT_TAG (78h), in order to identify the sensor, and 6 bytes of fixed data

(FIFO_DATA_OUT registers from (79h) to (7Eh)).

The DIFF_FIFO_[9:0] field in the FIFO_STATUS1 (3Ah) and FIFO_STATUS2 (3Bh) registers contains the number

of words (1 byte TAG + 6 bytes DATA) collected in FIFO.

In addition, it is possible to configure a counter of the batch events of accelerometer or gyroscope sensors.

The flag COUNTER_BDR_IA in FIFO_STATUS2 (3Bh) alerts that the counter reaches a selectable threshold

(CNT_BDR_TH_[10:0] field in COUNTER_BDR_REG1 (0Bh) and COUNTER_BDR_REG2 (0Ch)). This allows

triggering the reading of FIFO with the desired latency of one single sensor. The sensor is selectable using

the TRIG_COUNTER_BDR bit in COUNTER_BDR_REG1 (0Bh). As for the other FIFO status events, the flag

COUNTER_BDR_IA can be routed to the INT1 or INT2 pins by asserting the corresponding bits (INT1_CNT_BDR

of INT1_CTRL (0Dh) and INT2_CNT_BDR of INT2_CTRL (0Eh)).

In order to maximize the amount of accelerometer and gyroscope data in FIFO, the user can enable the

compression algorithm by setting to 1 both the FIFO_COMPR_EN bit in EMB_FUNC_EN_B (05h) (embedded

functions registers bank) and the FIFO_COMPR_RT_EN bit in FIFO_CTRL2 (08h). When compression

is enabled, it is also possible to force writing non-compressed data at a selectable rate using the

UNCOPTR_RATE_[1:0] field in FIFO_CTRL2 (08h).

Meta information about accelerometer and gyroscope sensor configuration changes can be managed by enabling

the ODR_CHG_EN bit in FIFO_CTRL2 (08h).

LSM6DSTX

FIFO

DS14039 - Rev 1

page 40/175

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