Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB ...

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I have an Atolla powered USB hub
https://www.amazon.co.uk/gp/product/B07B2HJG8P/ref=ppx_yo_dt_b_asin_title_o03_s01
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.  


Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
On 13/09/2020 17:30, NY wrote:
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Known problem:

https://www.raspberrypi.org/forums/viewtopic.php?t24%4900

One fix is to snip the red wire in the cable between the hub and the Pi.
--  
Dave

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
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I've read some reports that this doesn't always fix the problem, though from  
my understanding of the problem (hub wrongly continues to supply power to Pi  
when Pi's own PSU is unpowered) it *ought* to fix it.

Does anyone know whether the list https://elinux.org/RPi_Powered_USB_Hubs is  
relevant to the Pi 4? I can't find a revision date.  


Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
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Probably not:
https://elinux.org/index.php?title=RPi_Powered_USB_Hubs&action=history

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
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Ah! Forgot to check that history.

Incidentally, Dave's suggestion of cutting the red wire (presumably +5V)  
didn't work. I cut the red wire of a short male USB A - female USB A lead  
and inserted it between the hub and the Pi. But the Pi still fails to boot  
from power-off state if the hub is powered-up (irrespective of whether  
anything is plugged into the hub).

Any other suggestions? Pi Hut sell a 7-port powered hub which is said not to  
backfeed power from hub to Pi, but it's only USB 2, and I'll like to take  
full advantage of the Pi's USB3 ports if I have several discs, some of them  
USB3, all connected to the Pi through the hub.

Is it a problem that the Pi 4 is more susceptible to than the 3B+? Because I  
never encountered it with that.  


Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
On 13/09/2020 05:30 pm, NY wrote:
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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?


--  

Chris Elvidge, England

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
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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?  


Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
On 14/09/2020 11:19, NY wrote:

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There's a post on the forum thread I mentioned which states that the Pi  
must have all its power buses below 200mV in order to fully reset. It  
seems that power from the hub's USB data lines is leaking onto the Pi  
and causing the problem.
--  
Dave

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets

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Yes, whether they will work with low-draw devices like a Pi? I can't say.

There are power-saving mains switches/extension strips where you are  
intended to plug the "computer" into the master port, and other  
peripherals into the "peripheral" port(s). When the computer powers on,  
the peripherals come on a couple of seconds later. When the computer  
powers down, peripherals go off after a short delay.

The snag is, the one I have (free from eon/n-power?) continues to calibrate
itself based on current draw, not just a simple "0ma or something more" cutoff.

So when used with power tools (to activate an always-on vacuum cleaner  
for auto-dust collection), it can sometimes get confused as the load goes  
from zero, to "idling saw" (at which point it turns on), to "saw is cutting  
wood for 10 seconds" then back to "idling saw": and switches off, because  
the load dropped noticeably.  

Of course, I don't want it to shut off while the saw is still running :)
--  
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk  |    http://www.signal11.org.uk

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
On 13/09/2020 17:30, NY wrote:
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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?

Re: Pi4 won't boot *from power-off* if Atolla powered hub is plugged into any of the Pi's USB sockets
On 15/09/2020 10:16, js wrote:

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Should have mentioned that I had cut the red wire in the hub usb lead so
that it could not backfeed the Pi.

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