We currently want to realize a project using the MMA8451Q where the following happenes (very simplified):
- The accelerometer is in sleep-mode with a data-rate of 12.5Hz. Moreover, the transient acceleration detection is activated
- When a transient acceleration is detected, it wakes up and switches it's data rate to 800Hz. Also the µC gets an interrupt from the accelerometer and the µC starts collecting high-pass filtered data from the accelerometer at 800Hz to search for the highest (transient) acceleration detected
My question is the following: When the accelerometer wakes up it switches its data rate dramatically from 12.5Hz to 800Hz. According to the datasheet of the MMA8451Q the high-pass cut-off frequency relates on the data rate. So it is changed on an transient acceleration event as well.
My feeling tells me that this can impact the high-pass filtered data collected right after the transient acceleration event (even for frequencies well beyond the cut-off frequency). Is this correct? Does the change of the cut-off frequency invalidate the first high-pass filtered data from the accelerometer after the transient acceleration event?
It would very be interesting for me how the high-pass is implemented within the accelerometer. Unfortunately, I did not find any information in the application notes.
Thanks for any help!