Foxroyd
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Have I damaged my Pi when connecting USB hub? [Solved]

Wed Jun 06, 2012 11:50 am

Hi

I received my Pi a few days ago and have managed to boot OK with a download of debian6-19-04-2012.zip.
I had mouse, keyboard, HDMI and power connected,
I played with this for a couple of days with no problems and got LXDE running OK while I waited for delivery of a seven port USB hub. When this arrived I noticed that when I connected the Pi USB to the USB hub (input) the power LED on the Pi glowed even though the power to the micro USB on the PI was disconnected. Is this supposed to happen?
I used the Pi that evening but none of the USB connections from my new hub worked. When I turned off the Pi that night I accidentally left the USB hub power connected and powered up (red LED glowing).
Next morning I could not get the Pi to boot up at all.

Have I caused damage to my long awaited Raspberry Pi ?

bredman
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 12:07 pm

It seems that you have a badly-designed hub which is leaking current back up the cable. A well-designed hub should have a diode to prevent current flowing in the wrong direction.

The end result is that the current will have flowed through the USB polyfuse and blown it. The good news is that a polyfuse will reset slowly, it may take a few hours. Just leave it for six hours and try again.

In future, do not power on the USB hub unless the RPi is turned on. And turn off the hub before the RPi.

Or... Many people (myself included) have cut the red wire in the USB cable from the RPi to the hub. This prevents this problem.

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NickT
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 12:26 pm

To echo bredman's answer, I think it's very possible that you may have blown the polyfuse. I don't understand polyfuses very well so don't see why it didn't go immediately, but maybe that's just the way they are. (In my day fuses were either good or blown, they were made of wire, blew quickly and didn't repair themselves).



From reading the data sheet on the 9512 USB controller chip, it appears that it knows that the fuse has gone (section 2.2.2) and can signal the processor that this has happened. Whether the processor has then been programmed not to boot under these circumstances is unknown to me, but it could be the case. Perhaps someone with detailed firmware knowledge could expand on this?

Foxroyd
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 12:37 pm

Hi bredman

Thank you for your rapid response.

I just tried to boot up again (over a day later) and still no success. I re-read my post and noticed that I was not very clear.

When I try to boot up I do get the red power LED from my original power supply attached to the micro USB power input on the Raspberry Pi (hub is no longer connected) but I do not get anything on my TV screen to indicate that the Pi is booting up and I do not (after a minute or two) get the green OK LED to indicate success.

Any other ideas?

BTW it was a very cheap 7 port hub (£5 from ebay) so this may be the cause of the problem.

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Montala
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 12:45 pm

Foxroyd wrote:BTW it was a very cheap 7 port hub (£5 from ebay) so this may be the cause of the problem.
That is very possible, I'm afraid!

While some folks on here have had some success with these, one member reckoned they were (and here I quote!) "a pile of poo"!

I hope you do manage to sort things out OK though.

bredman
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 12:49 pm

If possible, try another SD card.

There is a chance that the SD card has been corrupted.

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piglet
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 1:01 pm

Montala wrote:
Foxroyd wrote:one member reckoned they were (and here I quote!) "a pile of poo"!
Sorry about that! My comment could have been worded better...

After pulling out pin 1 (+5V) on the lead to the pi to avoid exactly the issue you noted and running from a decent 3A PSU the Pluscom hub works OK, even if it does fall apart when you plug into it.

I've now got it in use as a passive hub on my PC and a rather better D-link one using the good PSU for the pi. The D-link PSU was about as bad as the Pluscom one.

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mahjongg
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 3:11 pm

I agreee with bredman, the chance that you have damaged the PI through a "backfeeding" hub is very small, there is a chance that the fuse for this port has blown, but even if it did nothing else would have happened, and even with a "blown fuse" the hub would still be able to communicate with the PI fine.
There is however a good chance that the contents of the SD-card got gobbled due to a "half working" PI.
Formatting and reprogramming the card should solve the problem.

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ScoobyDoo
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 4:34 pm

I had this issue, the surge from the usb hub corrupted the sd image.

Format the SD and re-image and all should be fine but bin that usb hub. I tried and it was a waste of time, im not using any hub, the safest thing is just to power the pi from a decent usb power adapter and only plug in lower power usb devices into the pi's usb ports.

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SN
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 4:39 pm

piglet wrote:
Montala wrote:
Foxroyd wrote:one member reckoned they were (and here I quote!) "a pile of poo"!
Sorry about that! My comment could have been worded better...

After pulling out pin 1 (+5V) on the lead to the pi to avoid exactly the issue you noted and running from a decent 3A PSU the Pluscom hub works OK, even if it does fall apart when you plug into it.

I've now got it in use as a passive hub on my PC and a rather better D-link one using the good PSU for the pi. The D-link PSU was about as bad as the Pluscom one.
Apart from the case falling apart (and it looks as cool as a Pi like this with no case - pictures to follow), I have no gripes with the Pluscomm but I strongly recommend using it as the power source (USB to microUSB AND USBA to B between hub and pi) for the Pi if you have the 3A PSU - then all power all comes on at the same time either side of the Pi AND you only have one mains plug too... shimples...
Steve N – binatone mk4->intellivision->zx81->spectrum->cbm64->cpc6128->520stfm->pc->raspi ?

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Montala
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 5:34 pm

SN wrote:Apart from the case falling apart (and it looks as cool as a Pi like this with no case - pictures to follow), I have no gripes with the Pluscomm but I strongly recommend using it as the power source (USB to microUSB AND USBA to B between hub and pi) for the Pi if you have the 3A PSU - then all power all comes on at the same time either side of the Pi AND you only have one mains plug too... shimples...
Just to be on the safe side, how about using a 'Y' cable to 'power' the Pi from two of the USB ports rather than just the one, as the output of each port is probably limited to 500mA anyway?

As it has seven, I think one can be spared for this purpose!

Foxroyd
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 6:13 pm

Thank you all very much for your help on this problem.

You have enabled me to get my Raspberry Pi back up and running. I have disconnected the 7 port hub and am running with my original configuration (mouse, keyboard, HDMI and 1000ma power supply to the micro USB). I formatted my 8gb SD card in DOS (this showed only 74mb size after formatting) then I used win32diskimager to write a new image of debian6-19-04-2012.zip onto the device and hey presto!!

FANTASTIC!!!

I still have the problem that I have run out of USB sockets and need to run a wireless internet connection.

From the information you have supplied I think I need a good 3A power supply and a USB 'Y' cable to proceed.
Am I right?
Where can I get these?

brian_reiter
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Re: Have I caused damage to my Pi when connecting USB hub?

Wed Jun 06, 2012 8:30 pm

Wish I I knew, the power issues are a pain. The difficulty in getting a good USB style power supply is frustrating, seeing as I have any number of regulated 5volt supplies I'm contemplating getting a breakout board for the USB and wiring the xxxxxxx thing directly. As I an testify, most cheap powered USB hubs and power supplies are crap.

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mahjongg
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Re: Have I damaged my Pi when connecting USB hub? [Solved]

Wed Jun 06, 2012 10:29 pm

The best solution is still to use the same 7 port USB hub you are using to extend the number of ports to power the PI. That way no "half powered" problems will occur, nu current will flow through the RPI's USB port if you connect power from the hub to the front micro USB power input. Its unlikely the 7 port hub limits the current to one of its outputs to strictly 500mA, but even if it does the PI should normally work fine, (it doesn't need to power its USB ports, so that helps a bit) only in extreme cases would you need an Y cable to get power from two hub output ports.
I would put the mouse on the remaining RPI's USB port.

The only chance you damage the SD-cards contents again is if you disconnect the power cord with the card running. Always do a regular software controlled shutdown, and only then power off the hub.

bredman
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Re: Have I damaged my Pi when connecting USB hub? [Solved]

Thu Jun 07, 2012 8:41 am

I agree with mahjongg, use the hub to supply power to the RPi.

However, you may need to use the spare port on the RPi for your keyboard. A lot of people have reported problems using a keyboard and WiFi device on the same hub.

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Montala
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Re: Have I damaged my Pi when connecting USB hub? [Solved]

Thu Jun 07, 2012 9:29 am

That is just what I was thinking of doing (when I eventually do receive my Pi!)

Using a powered hub to supply the Pi (possibly with a 'Y' cable)
Connecting my tiny Logitech Unifying receiver (for a K400 wireless touch keyboard) into the USB port on the Pi, with a short USB cable from the other one going to the hub.

Although I will probably test it first with a 'hard wired' Ethernet cable, I hope to be able to use a Edimax EW-7811Un wireless adapter, which I would plug into the hub.

This would then keep the two devices on separate 'hubs', as recommended.

Two questions then, firstly should this set-up work OK, and secondly, am I correct in thinking that by doing it this way I do not have to worry about cutting the 5v cable in the hub, or anything like that?

Thanks! :)

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