Re: Canoscan Lide 210 Scanner
On Thu, 30 Oct 2014 09:16:42 +0200
Johann Spies <johann.spies@gmail.com> wrote:
> This is not Debian specific, but as I experienced it on Debian and
> initially thought that it might be a Debian problem, it may help some
> other users.
>
> I recently bought the scanner specified in the subject line after
> reading that the saned team claims it has "complete" support. I
> first tried it out on my Desktop which has something like 8 usb2
> ports. I had limited success and was frustrated. Then I took it to
> work and tested it with my work laptop with 4 usb2 ports and it
> worked without a problem.
>
> At home I tested it on my other Debian laptop which have two
> usb3-ports and two usb2 ports. On the USB-3 port I experienced the
> same problems I had on my Desktop. Moving the connection to a
> usb2-port everything worked as expected.
>
> My thought on this is that on the Desktop there was not enough power
> coming through the usb-port and on the usb3-port there the power was
> too much.
It is astronomically unlikely that the USB supply voltage would be too
high, as almost certainly, the same supply is used inside the computer,
and a 5 Volt rail can't go any higher than 5.25 before other things
will stop working.
>
> This scanner only works with the electricity it gets through the
> usb-connection.
>
Something you could try is a powered USB hub, using a separate 5 Volt
supply. If the scanner works through the hub on the problem machine(s)
with external power applied but not without it, it's pretty certain
that's the answer. Computer USB ports are not all equal in terms of the
maximum current available, and at the moment, this does look the most
likely answer. I'm assuming you're using the same USB cable for all the
tests, at least on USB2, as scanners do shift a fair amount of data and
all USB cables aren't created equal, either.
I have two devices that came with USB cables with two type-A connectors
fitted at one end, as the 'guaranteed' minimum of 100mA from one port
isn't enough for them. But I've still had trouble, so I use them
through a powered hub every time now.
--
Joe
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