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ADXL345 and continue FF activation at fixed inclination Alpha angle

Question asked by Maurizio_IT on May 6, 2013
Latest reply on May 6, 2013 by Maurizio_IT

Dear Analog Support,

I have use ADXL345 and develop my firmware for Activity Daily Living (ADL) placed on peaple chest and it works well.

After that I merge firmware for ADL with source code by AN-1023 (Fall Detection Application by Using 3-Axis Accelerometer ADXL345).

Assuming that Y axis is the oriented to sky when peaple is stand-up.

As soon I setup a firmware to operate as ADL and Fall Detection, I see that there is a fixed angle (I call Alpha around 45degree) between ground plane and Y axis at which the FF Interrupt continue to be activated even the MEMs is fixed and stable. This phenomena happen also when I reset the mcu and reconfigure the ADXL345 (fixed position at Alpha angle).

Algorithm works for ADL using WATERMARK INT2 and 32 byte FIFO in Stream mode. Each time FIFO is full I read the values.

Fall Detection works as INT1 FF as AN-1023 sorce code.

 

Whenever moving the Y axis angle Alpha arrival triggers an interrupt FF despite moves slowly.

This continue to generate a false Fall Detection procedure for any crossing at angle Alpha of Y axis.

 

Can you help me to understand what is happening and what kind of test made to detect possible bugs or wrong configuration?

 

Thank you

Maurizio

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