Re: BUFFALO WLI-U2-KG54-AI USB adaptor stopped being 'recognized'

On Wed, 07 Mar 2007 10:28:07 -0800, Jeff Liebermann
<jeffl@xxxxxxxxxxxxxxxxxxxxxx> wrote in
<2k0uu25j7io892mv3drjbjuuuvsmjn4iot@xxxxxxx>:

Kev <invalid@xxxxxxxxxxxxxxx> hath wroth:

It's different on mine. I have 4 ports and it specifies that the Hub is
self powered and total power available is 500ma per port.
http://en.wikipedia.org/wiki/USB

If your external USB hub is powered by its own 5VDC power supply,
you'll get 500ma per port.

If there's no external 5VDC power supply plugged into the hub, your
total current consumption for the hub is limited to the 500ma that can
be supplied by the single USB port it's plugged into on the computah.

Where the problems start is that this is NOT a measure of the current
drain. It's the amount reported by the USB device inside the hub.
There's no provision for actually measuring the current other than to
protect the device from overload. So, a hub will report 500ma per
port as if there were an external 5VDC power supply plugged in, even
if the power supply is not present. The hub will not inititate an
overload shutdown, but the single port in the computah that's trying
to source more then 500ma will complain.

Of course, I don't have a single USB hub (powered or otherwise) handy
so I can't test this immediately. I'll try it later, when I drag
myself to my palatial office.

I just checked a small generic 4-port powered/unpowered hub, and it
reports 0 mA both in its own device manager entry and in the entry for
the root hub.

--
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