On 13/09/2020 17:30, NY wrote:
> I have an Atolla powered USB hub
>
https://www.amazon.co.uk/gp/product/B07B2HJG8P/ref=ppx_yo_dt_b_asin_title_o03_s
01
>
> which I bought to power a spinning HDD that I plugged into my Pi 3B+.
>
> I'm now using it in my Pi 4B. If the Pi is rebooted without shutdown and
> power-off/on, it boots fine. However if it is shutdown and then the
> power is
> removed and replaced (whether that is immediately or half an hour later)
> the
> Pi refuses to boot: the green LED does not come on and nothing appears on
> either HDMI output. If it is in that state and I unplug the hub, booting
> continues immediately, even if the hub is replaced immediately after being
> removed.
>
> 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.
>
> It is related to the hub rather than what is plugged into it. It happens
> even if the HDD and other devices are removed from it. Removing the
> power to
> the hub is sufficient to allow booting: maybe I need some means of making
> the mains to the hub delay coming on for a few seconds after power it
> supplied to the Pi!
>
> I'm wondering whether to buy a different make of hub, or whether I may find
> that this is affected in the same way.
>
> Does anyone know of a make of powered USB3 hub which is known to work
> with the Pi 4 after power-cycle?
>
>
>
> This is separate to the /etc/fstab auto-mount problem that I posted about
> yesterday. In that case, the Pi would *start* to boot and then fail at
> mount
> time; in this case there is no sign that the Pi is even beginning to boot.

I had similar problems. At some point in booting the pi powers up the
usb devices and it didn't seem to like the hub being already powered at
that point.
I made a usb lead with just the power lines connected. This was
connected to a spare usb socket on the Pi and was used to power a relay.
The relay switched on when the Pi powered up the usb lines and power to
the hub was routed through the relay contacts so that it powered up at
the same time. This worked OK.
The relay must be able to work on 5 volts and the one I used pulled
about 30mA.
I didn't try it but perhaps a logic level mosfet could replace the relay?

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