[Nut-upsuser] Weekend Puzzle: computer posing as an UPS

[Jim Klimov]

At least, the power-hungry RPi5 8GB model did boot and is running for a few
hours now. The USB3-capable ports on the MoBo probably are able to feed the
needed ~5A at 5V? I just pulled the USB-C cable near the fan (large enough
grill) from a connector near the keyboard to the Pi hanging inside the
well-cooled case.

Also note the PiKVM project (something I thought of but did not adopt here,
more HW needed) or some relative thereof, which may use a PCI card as a
dock for a Pi (maybe Compute Module). Though oddly the ones I've read about
used PCI only for power (and physical containment) but not as e.g. a way to
pose as actual PCI - a video card and other devices, all those needed
separate cabling anyway.

I suppose an (unmanaged) fan power socket, or one of ATX connectors, could
also be used. At least as an input to a demo PiJuice HAT I had lying around
(documented to accept 4V-10V from external sources), but it is too weak to
boot up an RPi5. Allegedly can run one if booted directly, did not try yet.

Jim


On Sun, Sep 15, 2024 at 6:31 PM Greg Troxel via Nut-upsuser <
nut-upsuser at alioth-lists.debian.net> wrote:

> Jim Klimov via Nut-upsuser <nut-upsuser at alioth-lists.debian.net> writes:
>
> >   I am experimenting with a Raspberry Pi, and it is fed from my PC
> > (Debian-ish Linux) that is in turn protected by an UPS - so runs NUT.
> >
> >   As far as the Pi is concerned, the bigger computer is its wall power
> > source (provides the USB socket) and being a smart machine with NUT
> > running, it could pose as an UPS itself. That is, if the big computer is
> > going to shut down (including probably rebooting, as I expect the
> > motherboard to power-cycle its USB ports), it should issue FSD on some
> > bare-bone driver *AND* wait for clients (like upsmon running on the Pi)
> to
> > disconnect before proceeding with its own power-off/reboot.
>
> Wow, I never would have guessed that this is a workable approach
> (running the Pi this way not the nut part).   Do you have ports that are
> more than 500 mA, and does the Pi (pi0?) really work with 5V 500 mA?
>
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