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ADXL372Z thresholds and Impact Detection

Question asked by PCote on May 16, 2018
Latest reply on May 17, 2018 by jwang





I have been working with the ADXL372Z for a while I have some questions to help me go forward. They should be simple:


1) The output of the chip either regular acceleration or max acceleration have to be converted to 12 bits then multiply by 0.1 (100 mg/code)?


2) The accelerometers have an offset value at startup? In absolute threshold mode, the threshold values programmed in the x,y,z registers must take into account that offset value? For example, if the offset value at startup is 2g, a threshold of 3g should be programmed as 5 (50 * 100mg/code)?


I am asking this question because I could not get the inactivity state to kick in with an inactivity threshold of less than 3.2 g. The spec says 0g offset  output could be -7 to 7g. I assume I need to read the values (x,y,z) at the start (non moving chip)  and include the offset it in the programming of the inactivity and activity threshold registers?


3) I programmed the chip for Impact Detection Capture as per page 19 of the data sheet. However, I am not sure when the data is ready. I assumed from documentation that the FIFO ready bit would be at 1 when ready to be read? I am not sure what is telling me the maximum values are ready to read.


4) Is it feasible to perform Impact Detection Capture without the interrupts? As an example using the chip in looped mode and I monitor the bits.


Many thanks