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Reliably detecting power-off/on with stm32l432

Question asked by brown.geoffrey.001 on Feb 28, 2018

The stm32l432 lacks the PORRSTF flag that other stm32 processors have, so I don't see a way to reliably detect a power-off/on event.  I tried parking a bit in the backup registers, but it doesn't appear that this is cleared without waiting for stray capacitors to discharge, which would be fine if I understood the threshold.  The reference manual includes this cryptic note about when the backup domain is reset:

 

"VDD or VBAT power on, if both supplies have previously been powered off"

 

But what levels ?   I need to know when a significant power glitch has occurred, but how ?

 

Is there a reliable test ?

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