Nut upsuser - Sep 2024 - Weekend Puzzle: computer posing as an UPS

Kelly Byrd <kbyrd at memcpy.com> writes:
> With USB-C ports and cables, there are a ton of profiles, I don't know
what
> the new Pi's support, but likely something like 3A @ 5V, 9V, or 12V
over
> USB-C
Up to the RPI4, I was pretty sure there wasn't PD, just 5V and it drew
what it drew, and you hoped that the supply was big enough.

It seems the RPI5 will use PD if given a capable supply.  Looks like 5V
5A, and it won't negotitate higher voltages.   There's an official
supply that does PD

 
https://www.newark.com/raspberry-pi/sc1153/power-supply-usb-c-5-1v-5a-white/dp/82AK3955

and the output spec is

  5A at 5.1V, 3A at 9V, 2.25A at 12V, 1.8A at 15V

  looks like a TUV seal



I find Jim's way of using this interesting, but my approach is totally
different.  First, when I'm using a Pi, it's because I want a low power
computer that I can leave on all the time, or can place in a different
physical location I don't particularly want to do things on a Pi instead
of a desktop.  And then I want it to be reliable.

That leads me to plug a power supply into a UPS, or to use POE (from a
POE switch which is plugged into a UPS).  For RPI3, I found a POE
ejector that splits the POE ethernet cable into ethernet only and a
micro USB.

> First, when I'm using a Pi, it's because I want a low power
> computer that I can leave on all the time, or can place in a different
> physical location I don't particularly want to do things on a Pi
instead
> of a desktop.  And then I want it to be reliable.
>
Well, this particular berry would be planted to the NUT CI farm, as well as
that PC already serving some of the build agents. So they are both on all
the time anyhow (and the Pi only has its power cable and wifi, maybe will
use ethernet - not desktop-y stuff). So it made sense to co-locate them
compactly.

Jim
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FWIW, a few lessons learned:

* Different USB-A sized ports (even if marked USB-3.2) did not prove a
stable source, with Pi5 occasionally turning off or rebooting. Sort of
behaved well for days, but as soon as I added load like package installs or
NUT builds, it did not survive 5 minutes...

* Might be the MoBo turning off or cycling the port due to
"overload"?..

* Tried the `usb_resetter` script (referenced in NUT contribs) and host
`dmesg` did show re-detection of keyboard etc., but a turned-off Pi did not
boot up. Did not check much further, but did harbor hopes that a funny NUT
driver could "shutdown/reboot" the USB port acting as an UPS for Pi...

* The Pi power socket is dumb-USB so the host does not "see" any IDs
about
it.

* Currently trying with a USB-C port on the MoBo, and a USB-C to USB-C
cable rated for 60W -- and so far it survived a few loops of NUT fightwarn
builds. Complains of undervoltage fairly frequently (every 30-60s), but now
did not crash yet.

Jim


On Mon, Sep 16, 2024, 13:57 Greg Troxel via Nut-upsuser <
nut-upsuser at alioth-lists.debian.net> wrote:
> Kelly Byrd <kbyrd at memcpy.com> writes:
>
> > With USB-C ports and cables, there are a ton of profiles, I don't
know
> what
> > the new Pi's support, but likely something like 3A @ 5V, 9V, or
12V over
> > USB-C
>
> Up to the RPI4, I was pretty sure there wasn't PD, just 5V and it drew
> what it drew, and you hoped that the supply was big enough.
>
> It seems the RPI5 will use PD if given a capable supply.  Looks like 5V
> 5A, and it won't negotitate higher voltages.   There's an official
> supply that does PD
>
>
>
https://www.newark.com/raspberry-pi/sc1153/power-supply-usb-c-5-1v-5a-white/dp/82AK3955
>
> and the output spec is
>
>   5A at 5.1V, 3A at 9V, 2.25A at 12V, 1.8A at 15V
>
>   looks like a TUV seal
>
>
>
> I find Jim's way of using this interesting, but my approach is totally
> different.  First, when I'm using a Pi, it's because I want a low
power
> computer that I can leave on all the time, or can place in a different
> physical location I don't particularly want to do things on a Pi
instead
> of a desktop.  And then I want it to be reliable.
>
> That leads me to plug a power supply into a UPS, or to use POE (from a
> POE switch which is plugged into a UPS).  For RPI3, I found a POE
> ejector that splits the POE ethernet cable into ethernet only and a
> micro USB.
>
>
> _______________________________________________
> Nut-upsuser mailing list
> Nut-upsuser at alioth-lists.debian.net
> https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/nut-upsuser
>
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