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

Sat Sep 28 23:29:56 BST 2024

Why do this what I set out to do?

  Partially for the challenge and fun, partially for the practical needs of
keeping that Pi safe, clean and cool - and inside a dust-filtered PC with
half a dozen big fans lazily and quietly doing their work seemed a good
spot. Planned destiny as part of NUT CI farm could also play a role (but
needs stability under stress).

  Partially also started from ideas about what to do with the Pi, e.g.
making a PiKVM (so it could also be a remote console and power-toggler to
that PC) which got ruled out by the stock of extra hardware suggested for
that particular job.

Jim

On Sat, Sep 28, 2024, 19:48 Tim Dawson <tadawson at tpcsvc.com> wrote:

> That, or use a low current source such as the fan header to control a 5v
> switch feeding the pi from a different source. Same net result, and no
> excess loads on your mobo. (Might be able to work this into the case using
> a spare power supply connector to feed it . . .)
>
> Still have not figured out why though, but that's not relevant to what you
> are trying to accomplish.
>
>
> On September 28, 2024 5:57:41 AM EDT, Jim Klimov via Nut-upsuser <
> nut-upsuser at alioth-lists.debian.net> wrote:
>
>> I guess I should scratch the idea about fan sockets as the power source:
>> they are rated typically at 0.2A each, so fan headers should be expected 1A
>> max (3A in some vendors/models), well under the 5A that the RPi5 wants.
>>
>> Jim
>>
>>
>> On Sat, Sep 28, 2024 at 11:52 AM Jim Klimov <jimklimov+nut at gmail.com>
>> wrote:
>>
>>> Follow-up:
>>>
>>> * Powering the Raspberry Pi5 from an USB-C port wired on the motherboard
>>> was much more promising, it survived over 8 hours building NUT in a loop
>>> (in a tmpfs). And in the morning I found it turned off (red light on the
>>> Pi).
>>>
>>> * Per
>>> https://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-with-linux
>>> it seems not possible to programmatically truly power-cycle USB port/hub,
>>> as 5V pins are "always on"; and per
>>> https://stackoverflow.com/a/16316401/4715872 - at least not on MoBo
>>> ports (some hubs may have invested into being fully up to spec and control
>>> power fully). The referenced uhubctl <https://github.com/mvp/uhubctl>
>>> on my PC said "No compatible devices detected!" so I guess that's it.
>>>
>>> * Whatever I could find with (suggestions welcome) `grep -r . `find
>>>  /sys/devices/pci0000\:00 -name '*usb*port*'` /sys/bus/usb/devices/`
>>> did not expose any differences beside timestamps with the RPi5 plugged and
>>> off, unplugged, and plugged back in again (with auto-boot). I hoped for
>>> some power draw statistics to at least learn which port it lives on, to try
>>> managing that somehow.
>>>
>>> * Overall, housing the Pi inside a cooled and somewhat dust-protected PC
>>> case seems a neat idea, but for powering the Pi, it seems I would need to
>>> use a real wall-power adapter (as noted many times on the net, ideally
>>> Raspberry's own one as others tend to vary in actual voltage provided under
>>> load).
>>>
>>> * But before that, I'm thinking if I could tap into the ATX power supply
>>> though (using "HDD" or "FDD" plugs) or fan sockets (could be individually
>>> manageable? gotta exempt one from OS/HW temperature-based mgmt then).
>>>
>>> Did anyone trod these side paths yet, any learnings? :D
>>>
>>> Jim
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Fri, Sep 27, 2024 at 4:43 PM Jim Klimov <jimklimov+nut at gmail.com>
>>> wrote:
>>>
>>>> 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
>>>>>
>>>> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
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