[iyonix-support] Re: USB ext hd & Fat32FS
- From: Chris F <c.n.l.f@xxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Thu, 14 Apr 2011 10:07:15 +0100
In message <4DA630F5.5010900@xxxxxxxxxx>
John Ballance <jwb@xxxxxxxxxx> wrote:
>>
> The USB rules are quite simple.
> A USB port must provide 1/2 amp if powered.. i.e. its in a box with
> connected power supply.
> If not so, i.e. it is a hub on the end of a USB lead, then if no power
> supply on this hub, total available power is 1/2 amp for the hub and any
> sockets on the hub.
> IF the hub has a power supply, then it can source 1/2 amp at each USB
> socket.
> It is not unusual for external devices to need more than 1/2 amp. The
> usual convention then is to have a power supply with this device.
> Occasionally you'll see a bodge that perhaps feeds off 2 (or more) USB
> sockets.
> Incidentally the USB stack interrogates the usb device and will only
> enable it if it reports as needing less power htan available on that USB
> socket.
> Hope that helps
I get it, I think;
The Iyo has 4 USB sockets. Each one may, or may not, be cabable of
providing 1/2A.
If I take just one of those sockets and attach my external drive and
it doesn't spin (and it doesn't) then it might if I use a double
headed usb cable and plug the double ends into 2 of the USB sockets.
However, IIRC, it's not usually a good idea to try drawing too much
current from electronic sources; so a more sound strategy should be to
take a USB extension lead from just one of the Iyo USB sockets, hang a
powered USB hub on its other end and use the (supplied) single ended
cable into one of the new hub's sockets.
If that doesn't work, substitute the double-ended USB cable and it
'should' work; and if it does, the SafeStore needs more than 1/2 amp
and it's now drawing its current from the 2 x 1/2amp available at the
usb sockets on the external hub.
Yes?
--
BW Chris F. [ British Iyonix, RISC OS 5.16 ]
Wakefield RISC OS Show - Sat 16/04/11 - www.wakefieldshow.org.uk
RISC OS: unified by diversion.
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