For the external source, if your
BB loses power, then you'll be powering it up through the esd does in the pin
connected to that external power source. It probably won't survive.
A general rule is to never apply voltage to a devices pin unless that device is
powered up, unless it is in the
The System Reference Manual (SRM) says you're supposed to gate all GPIO
(and other inputs) such that they aren't driven until either the SYS_RESET
line goes high (according to SRM section 7.1, 8.0, and possibly others) or
until the VDD_3V3B rail is up (according to SRM 8.6.2). Are these
