I'd like to detect the dynamic component of acceleration, i.e. the change in acceleration, and generate an interrupt when such change is detected. I see that MMA8451/2/3 calls this "Transient Detection".

However, I can't seem to find any other manufacturer supporting "transient detection". I've tried Analog, Kionix, STM, etc. Is it something exclusive to Freescale accelerometers or is it coined up by their marketing department?

I'm not certain of the mechanics, but "Transient Detection" seems to involve a HPF. Does that mean any accelerometer that has a HPF onboard will likely be equivalent to "Transient Detection"?


I believe the MMA8451 is a digital device since it supports I2C.

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    \$\begingroup\$ so the sensor gives you acceleration and you want the derivative of acceleration? derivative is just y[n] = x[n] - x[n-1] for sample n \$\endgroup\$ – endolith Oct 3 '15 at 0:34
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    \$\begingroup\$ Yes. I've only played with MMA8452, but 'motion detection' doesn't respond to gentle nudges. Transient detection can pick up even very slow acceleration because it takes out the dynamic acceleration component. I'm not sure if that's what HPF is supposed to do though. \$\endgroup\$ – Kar Oct 3 '15 at 0:41
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    \$\begingroup\$ HPF and differentiation are the same thing at low frequencies, but HPF flattens out at high frequencies. diff goes to infinite gain at infinite frequency. is this an analog or digital signal from the accelerometer? \$\endgroup\$ – endolith Oct 3 '15 at 1:11
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    \$\begingroup\$ ok in that case an analog differentiator: en.wikipedia.org/wiki/Differentiator#Active_differentiator \$\endgroup\$ – endolith Oct 3 '15 at 1:19
  • \$\begingroup\$ I see. How come HPF is differentiation for analogue MEMS? \$\endgroup\$ – Kar Oct 3 '15 at 1:21

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