USB causing Pi to hang

[davidmam]

I've been trying to use gphoto2 with a USB connected camera. After taking one shot, the USB seems to hang and not allow communicaiton. The Pi then hangs and becomes unresponsive via ssh or other methods.

Is this a known problem with USB on the Debian Squeeze kernel? It seems wrong that userland apps can hang the system.

[davidmam]

OK, having run a multimeter across the Pi it appears that my power supply (an HTC phone charger) is marginal when used with that cable (barely over 4.75V) and this drops to near 4.70 when USB kicks in to talk to the camera. Beefier PSU on order, and I'll try the other cable which gives 4.89V.

What would be really cool is a way to tell that the voltage is too low - maybe some GPIO hackery is called for.

[bredman]

The HTC chargers are generally good quality, I would suspect your power cable is the problem.

[jbeale]

Remember the input fuse is rated 700 mA (total for R-Pi plus any connected USB devices) and the two USB ports are fused at 140 mA each. There is a pretty clear consensus among Pi users that both these values are too small for many of the things people want to do with their Pi. (It was designed for basic keyboard and mouse only, anything else should use a powered hub.) If you're already using a powered hub, then the power supply, cable or input fuse is probably the issue.

The other "interesting" thing about the particular type of fuses placed here is that they can have a significant voltage drop across them, even below their "trip" current, and there seems to be quite a variation in their resistance. Do a Google search for "polyfuse site:raspberrypi.org" and you'll see some of the history of that issue.

[kid1000002000]

Just curious if that solved your problem? Having the same issue here.