Re: [PATCH 2/2] iio: imu: st_lsm6dsx: Decouple sensor ODR from FIFO batch data rate

Francesco Lavra
2025-10-10T07:13:09Z

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On Fri, 2025-10-10 at 00:30 +0200, Lorenzo Bianconi wrote:
> > The rate at which accelerometer or gyroscope sensor samples are fed
> > to the hardware FIFO (batch data rate, or BDR) does not have to
> > coincide with the sensor sampling frequency (output data rate, or
> > ODR); the only requirement is for the BDR to not be greater than
> > the ODR. Having a BDR lower than the ODR is useful in cases where
> > an application requires a high sampling rate for accurate detection
> > of motion events (e.g. wakeup events), but wants to read sensor
> > sample values from the device buffer at a lower data rate.
>
> can you please provide more details here? Are you using the hw fifo to
> read
> data? If we configure the hw fifo according to the BDR (even assuming the
> watermark is set 1) the hw will generate interrupts according to the BDR
> (bdr < odr).

Yes, I'm using the hw fifo to read data. The use case is to enable event
detection (which works best at high sampling rates) and sensor data
streaming at the same time, without requiring the data stream to be at the
same rate as the sensor sampling rate. So the amount of I2C (or SPI)
traffic (as well as the rate of periodic interrupts) required by the data
stream is kept to a minimum without sacrificing the accuracy of event
detection.

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