well one to power the RPi and one to connect to the hub for datawiiguy wrote:so i can just buy a 4 usb hub
use 1 of those usb to power the rpi and the other 3 i can use for other usb devices to connect on teh rpi ?
while still using teh second usb on teh rpi
one for the power i.e. usb to microusbBeerhunter wrote:Why two USB connections to the Pi?
That does not leave one for powering the Pi (one would not normally expect power to flow over the dedicated upstream port) unless the HD can get away with using only one port for power.Beerhunter wrote:(I hit go too quickly.) In addition to my question above, my four-port hub has a dedicated upstream connector leaving four free ports.
So: connection to pi via dedicated port and the remaining four: keyboard, mouse, USB hard disk.
Is that entirely right? That may work for non-compliant hubs, but compliant ones will only output 500mA per port without negotiating more (the pi doesn't) which is too low to power the pi. I worked round this by soldering a micro usb lead to the the hub's power input. A "Y" cable seemed too expensive and would have taken up two hub ports, and now I have all my hub ports free.mahjongg wrote:In short, yes.
You do expect too much power management from a simple hub!As an aside I suspect that most hubs will not provide the full 500mA of which they are capable without a proper negotiation
you will not get anywhere back powering the RPi from it's own normal usb socketsr4049zt wrote:I have not tested the upper of two usb sockets on the pi, but the lower got 3V not 5V when powered from the rPi board with a 5V 1A rated micro-usb power supply. Therefore I'd expect issues with trying to power an rPi from an external usb powered hub via the lower of its two usb sockets.
I have a 7-way usb hub with a mechanical switch on it to switch off the usb power connection between the rPi board and the hub. So far I have copied >2GB from one usb memory stick to another in Debian6 whilst that external usb hub was separately powered from four NiCad rechargeables at 5-ish volts. File transfers became unreliable when battery voltage fell below 4.4 Volts.