Design power off to prevent brown out - best practices asked

[kasper]

I'm making a light product and people should be able to pull the power directly (just with the main switch). Of course I don't want to lose important stuff. I was reading about EEPROM data that gets corrupted:

'EEPROM' persistence issue

Guys, Just thought I would throw this in - it might just help someone… I had this issue way back and decided that the EEPROM storage for long-term use was too ‘iffy’ ;-)). So - I designed my PCB to include a low-cost I2C FRAM (FerroElectric RAM) chip - works like a charm ;-)). These chips are WAY longer-life than FLASH or anything else - being measured in the trillions of write cycles and come in many sizes… Hope this is helpful to someone else ;-)). BR Graham

Are there any good practises to detect of a power supply is switched off? For example with a voltage sense circuit. Can I monitor that with an interrupt? And what then? Can I reset or do something else with the Photon (what?).

Adding a capacitor so the Photon still gets a bit of juice to shut everything down correctly?

Any best practices are welcome.