On Fri, 28 Feb 2014 09:45:42 EST Anthony Sorace <a...@9srv.net> wrote: > > Based on my own experience with USB weirdness with the Pi, I still suspec > power issues. How are you powering the Pi itself? Using a 1 amp supply yielded > problems, regardless of the sort of hub I had, which all went away when I > switched to a 2 amp supply. I'm told the second generation of these boards are > a bit better on that regard, but I don't have any to test.
The RasPi FAQ suggest 1.2A or more. In rev 2 they replaced two current limiting polyfuses with shunts so you can use a a powered hub or connect periphs requiring > 100mA. The RasPi wastes a lot of power. Its processor require 1.8V and only the USB requires 5V. For battery powered use people have tried a number of tricks to reduce power use: replace the onboard linear reg. with a switcher or two, tie 5V + 3.3V together and only use a USB periphs that runs on 3.3V & use model A Raspi -- the ethernet chip on model B draws a lot of power even when idle and you don't need it for wifi. Apparently Ralink RT5370 basedt cheapo wifi dongles can run on 3.3V. For robotics use we need a usb wifi driver!
