On Sat, Aug 10, 2019 at 9:50 PM Graham Haddock <[email protected]> wrote:
> What I would do is some minor surgery on the PocketBeagle, disconnecting
> the +5V lead coming in the microUSB connector.
> The easiest way to do this would be to remove FB1 (ferrite bead in series
> with USB +5).
> Easy with "hot tweezers", or a pair of small soldering irons.
> To restore the Pocketbeagle to factory configuration, solder FB1 back in.
>
>
Whatever instability problems you are seeing, I don't see this addressing
it. The PMIC is designed to dynamically switch between the P1.1 ("AC power"
in PMIC terms, which always bothers me because it is never AC, but instead
DC assumed to come from an AC-powered wall-supply). If somehow there's not
enough capacitance to make the switch cleanly, I'd suspect you are doing
something rather odd with the *load* you are putting on it. What else do
you have connected?
Anyway, I put both "AC" (P1.1) and "USB" (P1.7) on the headers on purpose
and the full expectation is that if you are putting a power supply in (and
it isn't a battery), you'll use P1.1. If it is battery, I also give you
that option at P2.14 (BAT).
> Short P1-Pin-1 and P1-Pin-7 together, and power the Beagle from whatever
> you are going to power it with at +5V.
> No issues with instability.
>
OK, now you are just asking for trouble. There's no justification for doing
that.
If the design isn't working as intended, then, let's talk about that and
details, such as what you are seeing on a scope and P2.13 (VOUT), which is
the output of the power mux on the PMIC, also referred to as SYS_5V on
BeagleBones. Ultimately, this is used to provide the power to the
regulators for the other subsystems. Perhaps your problem is drawing too
much current from it?
It can be argued I put too many power options on the header, but I tried to
keep it flexible for people embedding it onto something. You have a lot of
flexibility and I don't see any need to encourage people to alter the board.
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