LSM6DSTTR datasheet(60/180 Pages) STMICROELECTRONICS

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Functionality

LSM6DST

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DocID033525 Rev 2

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 on 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).

LSM6DSTTR Datasheet(PDF) 60 Page - STMicroelectronics