"Chris Elvidge"  wrote in message
news:rjndmk$et8$1@dont-email.me...
> On 13/09/2020 05:30 pm, NY wrote:
>> Has anyone some across this incompatibility? It's a bit of a bummer
>> because
>> it means the Pi will not auto-start in the even of a power-cut - unless I
>> am
>> present to remove/replace the hub.
>
> Yes, I've seen this but I stopped using USB hubs so can't test.
> "In the event of a power-cut." Won't the hub be powered down as well as
> the Pi? What happens if you shut the Pi down (shutdown -h now) and then
> remove/reconnect power to the hub, leaving all the other connections as
> they were?

I've yet to test a simulated power cut: shutdown Pi, then turn off both Pi
and hub, turning them on simultaneously as if power had been restored after
a power cut. I imagine it will be a boundary condition: depending on how the
Pi reacts, the fact that the hub has power *as* the Pi boots will either
just work or else just fail. I'll report back on this thread when I've had
chance to try a simulated power cut.

We went through a phase last year when there were frequent brief
interruptions to our village's supply because trees were shorting high
voltage lines somewhere in the area, tripping circuit breakers. Hopefully
that's been resolved now, but it will always be a weak point if a power cut
(when we're not at home) puts the Pi into a state where it will not reboot,
given that I will be using it as a PVR for recording TV. If I can't resolve
it by getting a hub that works OK with the Pi 4, I may have to go back to
using my older Pi 3 again for doing that job - luckily everything is still
configured on the 3. I suppose I could buy an external hard disc with its
own power supply, and dispense with the hub - as long as the disc itself
doesn't prevent the Pi booting if disc and Pi PSUs both turn on at the same
time.

The fact that a lead with the red 5V wire cut still experiences the problem
suggests that back-feeding of power from hub to Pi *may* be a red herring.
I'm wondering whether it's rogue negotiations on the data lines as the
devices start up. Goodness knows how that can be resolved.

Are there devices which delay the mains being turned on by a few seconds if
I need the Pi to be turned on just before the hub?

--- SoupGate-Win32 v1.05