[sane-devel] Canonscan N 650U LIDE Scanner does not scan but makes terrible noise

Andrea Vai andrea.vai at unipv.it
Thu Aug 29 06:14:53 UTC 2013

Hi, thank you for the reply. With the essential help from Gerhard we
seem to have found the issue. See below.

Il giorno mer, 28/08/2013 alle 20.29 +0000, coxster dillon ha scritto:
> The only thing I can think of, that maybe different between Sane on
> Linux and Twain on Windoze is simply perhaps the speed or more
> specifically the timing between commands issued.  I do not know the
> scanner API in detail enough to be more specific.  If you send the
> steps to the motor rather than say go to position Y, then the timing
> of those steps is probably important.

That makes sense, as Gerhard suggested me:
Are you able to compile the Plustek backend? If yes, you might play
with the following values in the file plustek-usbdevs.c @ line 2064 and

There you see the following:
** Canon N650U/N656U */
static HWDef Hw0x04A9_0x2206 =
        0.86,   /* dMaxMotorSpeed */
        0.243,  /* dMaxMoveSpeed  */

I would suggest to reduce the 0.86 to 0.80 or 0.76, compile and install
backend and try again - you should also test various resolutions.

Another suggested setting was to use 0.85 and 0.240...

I tried with 0.76/0.243 and it seems to work (20+ scans at various
resolutions without noise).

But now what? Which are the best settings? Do we have to assume that the
best settings are any that seem to be working, or use some criteria and
choose them among the ones mentioned above?

Winni, can you confirm that this works for you too?
> FWIW, In windoze I can use SnoopyPro which logs USB messages to
> scanner with timestamps.  So it could be measured to some degree.
...for example, might I try to do such a measurement, or it's not worth

Thank you very much,

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