Network settings - loosing connection

Hi,

I’m having trouble with network access with Riscos Pi. I’ve enabled access from the configuration tool, and rebooted. For a few sessions access with fine with Netsurf, Packman, !Store etc., but then in mid session the connection was dropped. I rebooted and check config, everything was the same, but reset the configuration just in case. This worked for a while before the same issue recurred. I finally took the precaution of downloading another copy of the R11 image and writing it to a different SD card, but had the same pattern repeat itself.

My network connection is via an Asus WL-330N Wireless-Ethernet bridge adapter using DHCP. It’s tested and working on other systems. I also tried the link with a different ethernet cable, but to no avail.

Has anyone else experienced this?

I have in a roundabout way, I would have times where networking just would start but then fail, or even not function at all, both on RO, Raspbian and RaspBMC images.

I had two issues – first was a PSU that wasn’t up to the job so when the CPU and GPU cranked up along with the USB ethernet it would just fail to work. Once I’d worked that out from measuring across the TP1 and TP2 points with a multimeter and finding something daft like 4v I got a decent PSU on it.

Next I found that my powered hub was a bit too cheap and nasty and that was interfering with the USB causing networking to fail and for massive CPU spikes – presumably because the CPU was being interrupted to deal with junk so often but swapping that out for a better one fixed that.

So, probably worth seeing if you get the same behaviour under another OS which will help nail down if it’s a RO issue or something more global – you could also fire up the PI with only the Ethernet connected and see if a continuous ping to it from another machine starts to fail.

Yeah, yours was probably a network issue Dan :-p

Thanks for the heads up. At the moment the Pi is simply being powered via a laptop, with no USB hub (just keyboard and mouse plugged into the Pi itself). I just got a powered USB hub today, so I’ll give it a try from that and see what happens.

Ah, powering a Pi from a laptop is probably not going to cut it.
It’s definately worth investing in a >1A PSU as well, otherwise you will have random crashes and events happening.
I think the one I got was 2A (probably not needed that high)
Phone chargers/laptops don’t usually cut it, they can barely charge a phone (or mine anyway)

I concur. You want to watch the quality of the USB leads too – long skinny ones (like the one from my Kindle) drop a lot of voltage across them – I have an Amazon Basics lead that is nice and thick and works well.

See Mal – It’s never a Network Issue™ :-P :-P

Sounds like a voltage drop causing the USB module to reset. I wouldn’t trust any PSU / lead when it comes to the Pi, the only way to be sure is to measure the voltage across TP1 / TP2 when you’re using it, if it drops below 4.75v, its not getting enough voltage.

Even the official Farnell Pi PSU doesn’t provide enough voltage, that’s how bad things are!

Working happily on a 2 amp hub now :) – Wasn’t aware the Pi was so power hungry!

I’m not sure whether the Pi is so hungry, it maybe that the voltage coming from normal USB sources is fairly “dynamic”. So it maybe able to supply enough power most of the time, but sometimes it may fall off – and that causes the Pi to freak, as I don’t think there is any voltage smoothing circuitry on it [don’t know if that’s the right termininology] )
Also I had problems with some USB devices, the USB wifi dongle used loads of power. I’ve heard some keyboards & mice can be problematic, but this isn’t an area I’ve had any issues with.
I got a powered USB hub and a separate Power adapter eventually, and since then I’ve not had any problems with stability.
I also think some of the power supplies are “optimistic” with their ratings as well.

If I had a volt/amp meter it would be interesting to see the load etc. and see how good the various hubs/psu’s are….

AIUI from posts on the newsgroups, the Pi has a 1A fuse on its power connector. Therefore it’s limited to a bit over 1A.

However, that isn’t quite the end of the story. A 1A PSU with 5% regulation might have dropped to 4.75V on its output when doing 1A. A 2A PSU with 5% regulation may only drop to 4.875V when doing 1A. The relationship probably won’t be that linear, but it gives the idea.

There’s also the issue of resistance in the connections: anecdotally, the Pi’s USB power connector isn’t that great at “high” currents, and many USB cables aren’t either. You only need 0.25R series resistance in total to drop 5V down to 4.75A at 1A; that’s not much.

As others have said, you would need to measure the voltages on the Pi and along the way from the PSU using a DVM to work out what is going on.