AnsweredAssumed Answered

LIS2DS12 - Discontinuous FIFO data

Question asked by Attila Szabo on Feb 23, 2018

Hi everybody,

in our application we use the LIS2DS12 sensor and we would like to perform a continuous long term data acquisition at high data rate. In order to achieve it, we use the LIS2DS12 in Continuous mode at 6400 ODR. The used communication is 4 wired SPI at 5 MHz. The FIFO_THS is set to be 128 and INT1_THS is activated. Until this point the chip works perfectly, I got the external interrupt, when there is 128 sample in the FIFO and I can read these X-Y-Z samples from the FIFO correctly and convert them into engineering format (IF_ADD_INC is enabled). During the tests we observed that the data is discontinuous and it missis 7-8 samples between the adjecent 128 X-Y-Z readouts. This 7-8 missing sample is corresponds to the time while I read the FIFO via SPI. The calculation: (1 cmd byte+128samples*6byte)*8bit*1/5MHz = 1.23 msec <=> 1/6400*8 sample = 1.25 msec. It seems us that the chip freezes the data acquisition during the read process (BDU is set to 0). Had anyone a similar observation? Because the datasheet doesn’t mention any freeze in the measurement during the readout process and it doesn’t declare that the readout should last less than 1 ODR time.

Thank you in advance for any help!

Outcomes