LSM6DSV80X datasheet(38/181 Pages) STMICROELECTRONICS

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6.8

FIFO

The presence of a FIFO allows consistent power saving for the system since the host processor does not need

continuously poll data from the sensor, but it can wake up only when needed and burst the significant data out

from the FIFO.

The LSM6DSV80X embeds 1.5 KB of data in FIFO (up to 4.5 KB with the compression feature enabled) to store

the following data:

•

Gyroscope

•

Low-g accelerometer

•

High-g accelerometer

•

External sensors (up to four)

•

Step counter

•

Timestamp

•

Temperature

•

FSM events

•

High-g accelerometer peak value

•

MLC features, filters, and results

•

SFLP output data (quaternion, gyroscope bias, gravity vector)

The applications have maximum flexibility in choosing the rate of batching for physical sensors with FIFO-

dedicated configurations: low-g accelerometer, gyroscope, and temperature sensor batch rates can be selected

by the user. Writing external sensors in the FIFO can be triggered depending on the sensor hub rate chosen or by

an external sensor interrupt. The step counter can be stored in the FIFO with an associated timestamp each time

a step is detected. The status of the FSMs when they are generating an interrupt event can be stored in the FIFO,

as well as the long counter overrun event or the long counter value when a specific command is executed from

one FSM, all associated with the timestamp value. The high-g accelerometer peak value detected from the high-g

peak tracking feature is stored in FIFO. Results from SFLP (quaternion, gyroscope bias, gravity vector) can be

stored in the FIFO at the rate selected for the algorithm. Moreover, MLC features, filters, and results can be

enabled to be stored in the FIFO. It is possible to select decimation for timestamp batching in FIFO with a factor of

1, 8, or 32.

The reconstruction of a FIFO stream is a simple task thanks to the FIFO_DATA_OUT_TAG byte that allows

recognizing the meaning of a word in FIFO.

FIFO allows correct reconstruction of the timestamp information for each sensor stored in FIFO. If a change in the

ODR or BDR (batch data rate) configuration is performed, the application can correctly reconstruct the timestamp

and know exactly when the change was applied without disabling FIFO batching. FIFO stores information of the

new configuration and timestamp in which the change was applied in the device.

Finally, FIFO embeds a compression algorithm that the user can enable in order to have up to 4.5 KB data stored

in FIFO and take advantage of interface communication length for FIFO flushing and communication power

consumption.

The programmable FIFO watermark threshold can be set using the WTM[7:0] bits in the FIFO_CTRL1 (07h)

read to detect FIFO overrun events, FIFO full status, FIFO empty status, FIFO watermark status, and the number

of unread samples stored in the FIFO. To generate dedicated interrupts on the INT1 and INT2 pins of these status

events, the configuration can be set in INT1_CTRL (0Dh) and INT2_CTRL (0Eh).

The FIFO buffer can be configured according to seven different modes:

•

Bypass mode

•

FIFO mode

•

Continuous mode

•

Continuous-to-FIFO mode

•

ContinuousWTM-to-full mode

•

Bypass-to-continuous mode

•

Bypass-to-FIFO mode

Each mode is selected by the FIFO_MODE_[2:0] bits in the FIFO_CTRL4 (0Ah) register.

LSM6DSV80X

Functionality

DS14764 - Rev 1

page 38/181

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