When upgrading firmware the hat makes an electronic resonating noise. It is high pitched, just as if a PSU is broken. After flashing however, it stops and all is fine.
Should I be worried?
Hey Jamos,
I’m not an embedded engineer so this is mostly speculation, but…
The firmware on the hat will be stored in EEPROM (Electronically Erasable Programmable Read Only Memory: a bit an oxymoronic name admittedly but I don’t define these things ha!).
Anyways, when the firmware is updating there is a lot of processing being focused towards the EEPROM, so that is likely the cause of the sound. Shouldn’t be too much to worry about. 
Regards,
Daniel
Ok great! I do have another UPS for another project so I’ll try that one as well. Thanks for taking the time to answer…