George_P
Posts: 10
Joined: Sun Jun 16, 2013 12:11 am

Powered USB hubs etc

Wed Apr 01, 2015 12:16 am

Hello,

A few weeks ago I aquired the Pi2, my second Pi and I have to say I am generally very happy with its performance.
There are a few questions regarding its setup and use...

One problem I have is to find a suitable powered hub. I bought one of those 7 port hubs (silver, upright with stand- lots of those on various internet sites), as it promised 3 amp (!!) current supply. I intend to connect everything USB to the hub and then to the Pi2, like I did with my first Pi.
I have a problem though... If I power the hub first and then the Pi, I get lots of errors (I/O errors, exec format errors interrupts errors and so on, and the Pi is lost... If I pull the Pi2 power cable the Pi2 continues to be powered apparently through the USB HUB!!!!!
If I power the Pi2 first and then power the hub or connect it after the Pi2 boot everything is OK!!!!
Is there a conflict with the power supply here??? Should I modify somehow the cable connecting the hub to the Pi2, disconnect the red power wire and leave only the signal wires?
I have to say here that if I use the powered hub supplied by Maplin -that triangular one- (I bought my previous Pi as a complete kit from Maplin) everything is OK.
There is a problem here.... You cannot say the USB hub is suitable until you use it ie open its pack.. if unsuitable it cannot be retuned! Same goes for some power supplies advertised as suitable for the Pi but useless in practice – giving the same sort of errors at boot!!!
Another problem associated with the hub is that if the Pi is left for some time on without any activity, USB devices connected to the hub do not respond, I have to disconnect the hub from the Pi port, reconnect and then they become active again.
I never had this kind of problem with the Pi1!!

Another question regarding the I/O pins.... Can I use all the GPIO pins as digital I/O?

And a final question.... As soon as the graphic interface starts I get a dialog box with the following error:

GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject

What does it mean and how can I get rid of this?

Many thanks

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MarkHaysHarris777
Posts: 1820
Joined: Mon Mar 23, 2015 7:39 am
Location: Rochester, MN
Contact: Website

Re: Powered USB hubs etc

Wed Apr 01, 2015 12:30 am

I have a problem though... If I power the hub first and then the Pi, I get lots of errors (I/O errors, exec format errors interrupts errors and so on, and the Pi is lost... If I pull the Pi2 power cable the Pi2 continues to be powered apparently through the USB HUB!!!!!
NEVER power the RPi by backfeeding the power from the hub... this might cause damage, and usually the backfeed is not sufficient to power the RPi. Always power on the RPi first using a 2.2 amp power source (wall wart 5v micro usb).
If I power the Pi2 first and then power the hub or connect it after the Pi2 boot everything is OK!!!!
Yes!
Is there a conflict with the power supply here???
See above.
Another problem associated with the hub is that if the Pi is left for some time on without any activity, USB devices connected to the hub do not respond, I have to disconnect the hub from the Pi port, reconnect and then they become active again.
You'll have to decide which hub you prefer, obviously.
I never had this kind of problem with the Pi1!!
You have my sympathy.
Another question regarding the I/O pins.... Can I use all the GPIO pins as digital I/O?
Yes. That is why they are called General Purpose Input Output pins. Its just that some of the GPIO pins ALSO have specific purposes too... and you cannot use them for BOTH at the same time. For instance you cannot use the TX pin in a serial comm session and use it as a digital output pin at the same time!
And a final question.... As soon as the graphic interface starts I get a dialog box with the following error:
GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject
Join the club. As soon as I get it figured out, I'll tell you too. Mine has been doing this since I upgraded Raspbian last night. rats.
What does it mean and how can I get rid of this?
marcus
:ugeek:

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rpdom
Posts: 17424
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Powered USB hubs etc

Wed Apr 01, 2015 8:12 am

George_P wrote:I bought one of those 7 port hubs (silver, upright with stand- lots of those on various internet sites), as it promised 3 amp (!!) current supply.
If it's the sort I think it is, then they can be rubbish.

I bought one to see what they were like and was amazed by how bad it was. The hub itself was unreliable and badly built. Two of the sockets didn't line up with the holes in the case and a couple of the solder joints were bad. The power supply that came with it claimed to be rated at 1A (1000mA), but couldn't even supply 5V at 100mA and dropped to under 3V at 200mA. I opened the PSU to check and it was completely unsafe to use - insufficient insulation between the mains and output, no proper regulation on the output voltage, very thin wires (the live one fell off when I opened it) and no fuse at all.

Even with a decent PSU, the hub was still unreliable and four of the ports were stuck on 12mb/s speed.

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