My Raspberry Pi had been behaving itself on the ‘hardware’ side since I took possession of it, weeks ago. After reading about limitations of USB connectivity, I obtained a reasonably-priced powered USB hub, with the intention (not surprisingly!) of connecting more things – including testing the possibility of USB sound..
So…. I connected the USB hub, and all was well.. (Re) connected the mouse dongle… all still OK… Connected the USB sound card – nasty ‘hub error’ warnings on the console!
So I did what you would normally do… disconnected the hub and re-booted the Pi.. But.. all I got was a single red led.. nothing else happened.. Tried re-connecting power (several times) … still nothing.. Tried booting with a different power supply – still dead… I took out the (Fedora 17) SD Card and put it in the card reader on my main (x86_64) system, and it appeared to mount and display correctly, so no (apparent) corruption there…
The Pi forum suggested I re-format another SD Card with Debian and try that… I was already thinking along those lines, but as I am not a great fan of Debian, I simply used the OpenELEC XBMC build, as it takes up less space, and my spare/spare SD Card is only 2GB..
Thankfully, this booted OK… So – at least the Pi wasn’t completely dead…
I than examined the contents of the non-booting Fedora card, and found to my surprise that kernel.img was missing from the boot partition! This (of course) explains why it would not boot, but how did this happen? I also noticed that some of the other files had dates of 1/1/1980, which was also odd..
So.. I copied across a known/good kernel.img file, and now everything works OK again.
That still leaves the question of the hub fiasco… After more research, it seems that the ‘just plug in any phone charger’ advice for the Pi power supply is not good, as many of these are of inferior voltage etc.. It needs a good 5V supply, or things start to fail.. I had tried several different phone chargers, but now use a 5V – to – USB power adaptor – the kind that has a USB slot in it.. This seems to work OK, but the hub still gives errors as soon as I try to plug the USB sound card in..
I should mention that this combination works just fine on my other Linux systems, with no errors…
The conclusion – so far – is that the Pi is rather fragile when it comes to power supplies and USB connectivity, and in some cases problems with these can cause the network link to fail as well, as the Ethernet adapter is actually an (internal) USB device..
So – now I need to dig out my trusty old circuit tester, and check all those voltages! More to come, soon….