I am creating a HAT which uses a USB cable so there are some scenarios where it might be useful to supply 3V3 into the PEX 3V3 from the hat. Without the battery/pokitto usb cable connected this works fine but I can’t find a schematic which covers battery protection where 3V3 is supplied. I saw mention in a previous post of short circuit protection so maybe it’s covered.
Anyone know if this would be safe?
I have powered Pokittos from J-Link connected to the PEX which is basically the same thing you are asking. No issues.
What kind of Hat? Heavy power usage? Something cool?
I’m quite curious 
How to explain… it’s a bit like the matrix… I will have to show you. ( Soon but I am on vacation shortly… ) One easy to explain feature is the integrated ISP programmer which enables the pokitto to be programmed from a browser via WebSerial. More soon.
Hopefully it is the paradise matrix, and not the nightmare one.