AN4650 datasheet(86/102 Pages) STMICROELECTRONICS

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First-in first-out (FIFO) buffer

AN4650

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Bypass-to-Continuous mode is sensitive to the level of the interrupt signal and not to the

edge, which means that if Bypass-to-Continuous is in Continuous mode and the interrupt

condition disappears, the FIFO buffer returns to Bypass mode. It is recommended to latch

the interrupt signal used as the FIFO event in order to avoid losing data (the interrupt signal

has to be driven to the interrupt pin so that the latch function takes effect).

Follow these steps for Bypass-to-Continuous mode configuration (if the accelerometer /

gyroscope data-ready is used as the FIFO trigger):

Configure one of the events as previously described;

Choose the decimation factor for each sensor through the decimation bits in the

FIFO_CTRL3 and FIFO_CTRL4 registers (see Section 8.3 for details);

Choose the FIFO ODR through the ODR_FIFO_[3:0] bits in the FIFO_CTRL5 register.

Set the FIFO_MODE_[2:0] bits in the FIFO_CTRL5 register to 100b to enable FIFO

Bypass-to-Continuous mode.

Figure 27. Bypass-to-Continuous mode

Once the trigger condition appears and the buffer switches to Continuous mode, the FIFO

buffer continues filling. When the buffer is full, the FIFO_FULL bit is set high.

Bypass-to-Continuous can be used in order to start the acquisition when the configured

interrupt is generated.

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