Steve-o
Posts: 15
Joined: Tue Mar 06, 2012 8:24 pm

Issues with USB and Ethernet

Thu May 17, 2012 12:51 pm

Hey everyone,
I luckily received my pi yesterday. Everything I tried until now including XBMC worked fine.
I am trying to setup my USB peripherals but as soon as I plug in my powered USB hub, ethernet fails. dmesg shows hundreds of "eth0: event 4 may have been dropped". All USB devices are however discovered without errors.
I am quite sure that this is not a power-related issue because the devices aside from the hard disk are low-power devices. If I unplug the usb hard disk it still fails.
Edit: Ethernet even breaks if nothing is attached to the hub. The hub is a 7 port hub from Belkin - are these incompatible?
Edit2: It seems like my Pi does not like usb hubs at all. The other no-name brand hub I have lying around also breaks the network connection with no devices connected. Having the usb hub's power supply connected/disconnected does not make a difference either.

Any Ideas?

Attached to the usb hub are:
- wireless keyboard
- wireless mouse
- usb soundcard
- usb IR-receiver

theunit
Posts: 31
Joined: Fri May 11, 2012 7:52 am

Re: Issues with USB and Ethernet

Thu May 17, 2012 1:07 pm

This could still be a power issue. The USB hub, even if self powered, has the potential to draw up to 500ma from the RP. The RP can only supply up to 100ma.

I have just hacked my hub to isolate its power from the RP but haven't tested it yet. Hopefully this will fix the problem

Another thing is there have been reports of a possible firmware problem with the USB/ethernet (same chip), so it could also be that. If my hub mod does not fix things then it is likely a firmware issue.

EDIT:
The USB definition says that when a bus-powered hub is connected it asks for 100ma and then once configured it draws 500ma. The current draw is not clearly defined for self-powered hubs.

This seems to be a very common issue. Maybe some hubs will draw less than 100ma when self-powered, but my guess is that most don't.

Steve-o
Posts: 15
Joined: Tue Mar 06, 2012 8:24 pm

Re: Issues with USB and Ethernet

Thu May 17, 2012 2:15 pm

You might be right. How did you isolate the pis power from the hub? By cutting the 5V wire?

Edit: I isolated the 5V point in the usb connector. The Belkin hub does not seem to start up without 5V from the host. The other one connects, but as soon as I connect something it throws errors in dmesg.
Did anyone actually get an usb hub to work?

Steve-o
Posts: 15
Joined: Tue Mar 06, 2012 8:24 pm

Re: Issues with USB and Ethernet

Thu May 17, 2012 2:54 pm

Ok I tried around some more. I found an USB-Y-cable from an external hard drive. I used that cable to connect the hub to the rPi but it still would not work.

So I disconnected the rPi from its power supply. Interestingly, the rPi was still up and running.
So the usb hub delivered enough power to also supply the rPi without its own supply connected!

prodata
Posts: 154
Joined: Tue Jan 24, 2012 5:53 pm
Contact: Website

Re: Issues with USB and Ethernet

Thu May 17, 2012 3:17 pm

Steve-o wrote: So I disconnected the rPi from its power supply. Interestingly, the rPi was still up and running.
So the usb hub delivered enough power to also supply the rPi without its own supply connected!
Yes, I've noticed that too, with a Logik (PC World) powered hub. I needed to connect four USB devices (KB/mouse/USB key/data input) so had to use a hub. Decided at one point to cold-reboot the Pi, so disconnected the Pi power only to discover that it was all still working. Slightly unexpected but perhaps not too surprising.

Steve-o
Posts: 15
Joined: Tue Mar 06, 2012 8:24 pm

Re: Issues with USB and Ethernet

Thu May 17, 2012 4:39 pm

prodata wrote: Yes, I've noticed that too, with a Logik (PC World) powered hub. I needed to connect four USB devices (KB/mouse/USB key/data input) so had to use a hub. Decided at one point to cold-reboot the Pi, so disconnected the Pi power only to discover that it was all still working. Slightly unexpected but perhaps not too surprising.
Yes I guess that is nothing to worry about. But I think it is a sign that my USB issues are software related and not caused by a weak power supply.

theunit
Posts: 31
Joined: Fri May 11, 2012 7:52 am

Re: Issues with USB and Ethernet

Thu May 17, 2012 5:35 pm

When your hub doesn't work when you cut the +5V, it's a clear sign that the hub was drawing power from the RP! It is exactly what happened with mine.

I have now soldered an extra wire in my hub so the external power supply connects to the would-have-been-there USB 5V. Haven't got to testing it yet. However, now it will be totally isolated, I know that any problems are firmware related and not power related.

There is some kind of issue with a mix of high/low speed usb devices which has apparently been fixed in the kernel.img in github. I already tried this but still had problems which is why i suspected the power issue. Either that or there are still further firmware problems.

Steve-o
Posts: 15
Joined: Tue Mar 06, 2012 8:24 pm

Re: Issues with USB and Ethernet

Thu May 17, 2012 6:09 pm

theunit wrote:When your hub doesn't work when you cut the +5V, it's a clear sign that the hub was drawing power from the RP! It is exactly what happened with mine.

I have now soldered an extra wire in my hub so the external power supply connects to the would-have-been-there USB 5V. Haven't got to testing it yet. However, now it will be totally isolated, I know that any problems are firmware related and not power related.

There is some kind of issue with a mix of high/low speed usb devices which has apparently been fixed in the kernel.img in github. I already tried this but still had problems which is why i suspected the power issue. Either that or there are still further firmware problems.
I have two hubs, one of them did not work without the 5V connection. But the other one was even powering the rPi when the rPi was not connected to its supply.

Thanks for the note about the kernel.img - is there a newer one available on github than in the latest debian release?

theunit
Posts: 31
Joined: Fri May 11, 2012 7:52 am

Re: Issues with USB and Ethernet

Thu May 17, 2012 6:37 pm

Thanks for the note about the kernel.img - is there a newer one available on github than in the latest debian release?
Yes it is much newer, in fact the current kernel.img was built a day ago!

Link: https://github.com/raspberrypi/firmware ... aster/boot

Return to “Troubleshooting”