Jason:
The PocketBeagle will do this, when powered from a serious Lab-bench power
supply running into P1-Pin-1, with added capacitance on the pin, without
added capacitance on the pin, without any other accessory or cape drawing
power from the PocketBeagle. I reported this in November 2017, and there
have been three or four other reports by other users since then. It makes
the PocketBeagle unusable for any serious application, where it is not
powered from the microUSB connector.
--- Graham
==
On Mon, Aug 12, 2019 at 9:34 AM Pablo Rodriguez <pabloar1...@gmail.com>
wrote:
> Hi,
> The past year i have to power 3 pocketbeagle from Vusb because of the
> random reset when connecting to Vin. This was the only thing that worked
> for me. Did a lot of testing adding capacitance and non work.
>
>
>
> El lun., 12 ago. 2019 a las 10:52, Jason Kridner (<
> jkrid...@beagleboard.org>) escribió:
>
>> On Sat, Aug 10, 2019 at 9:50 PM Graham Haddock <gra...@flexradio.com>
>> 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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