Re: USB interface question.
- From: "Roger Hamlett" <rogerspamignored@xxxxxxxxxxxxxxxxxxx>
- Date: Sat, 10 Jun 2006 15:27:42 GMT
"siliconmike" <siliconmike@xxxxxxxxx> wrote in message
news:1149930411.747592.301740@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I'm newbie at USB, if someone can help it would be wonderful:Start at the beginning. UPS, is a _point to point_ interface. There can
I'm envisioning a gadget that would take input from a USB port on a PC
(or any USB host). And it would act as a UPS for four downstream USB
devices, providing currents upto 1A.
In other words, the gadget would have 4 USB sockets for output, capable
of providing upto 1A to devices connected to it.
I have done some reading on USB but would like to ascertain whether the
gadget needs to have a controller / or can it be a passive device, as
far as the USB interface circuitry is concerned ?
(of course, the gadget would have its own separate supply, from where
it will derive the UPS power)
only be one USB device on a 'leg'. To have multiple USB devices from one
host, requires a hub.
Now other people have then pointed out that 1A, is more power than the
target device is allowed to draw off USB. 0.5A max, and even this requires
negotiation (though a hell of a lot of hubs, will supply this power
without comment). You could potentially use two USB sockets, and draw 0.5A
off each, but realistically, the simplest solution, will be a seperate
power connection for the devices. However it actually sounds as if the
devices will be normal USB units, in which case you might as well reduce
your power capabilities to 0.5A each...
Best Wishes
.
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