[sane-devel] Q: improving epson2 for Epson 12000XL

Olaf Meeuwissen paddy-hack at member.fsf.org
Mon Sep 28 10:27:39 BST 2020

Hi Wolfram,

Wolfram Sang writes:

> Hi Olaf,
>> Sorry for not chiming in earlier.
> No worries, I'm happy you gave me additional pointers.
>> I have been involved with development of the third-party epkowa and
>> utsushi backends for many years.  A lot of the protocol is documented in
>> the code for the utsushi backend via doxygen source comments.  See
>>   https://gitlab.com/utsushi/utsushi/-/tree/master/drivers/esci
> Ok, more documentation sounds nice. I still have questions about the
> gamma tables. I will check.
> One thing I could not find out yet: are there any advantages for me when
> I use epkowa? I think epson2 does a nice job and it can easily be extended?

If you only use the 12000XL, then there are no advantages to using the
epkow backend.

>> # I guess I could add a job to publish the documentation in a more
>> # accessible format via GitLab Pages.  Please submit an issue if you
>> # would like that.
> Well, if it is just for me, I like to read code, so not really needed.
> But for others, it might be helpful. Then again, you probably are not
> short of tasks.


>> There are two documented values: 0xff for autofocus and 0x40 for setting
>> it to the glass plate.  Other values appear to be allowed.
> And they make sense. Using the extreme values I get blurred images.

Actually, I've found a reference in my dead tree specs that all other
values with the one byte limit are supported.  0x00 through 0x39 are
below the glass plate, 0x41 through 0xfe are above.  Units unknown but
based on your observation of 0x59 being 25 steps away from 0x40 and it
corresponding to 2.5mm, I'd hazard a guess its 0.1mm assuming a linear

>> > The only question left for me now: Should focus/autofocus settings
>> > really have CAP_ADVANCED?
>> That's debatable indeed but I'd say CAP_ADVANCED is appropriate for most
>> users.
> Ok, then, I'll keep it!
> Thanks,

Welcome and hope this helps,
Olaf Meeuwissen, LPIC-2            FSF Associate Member since 2004-01-27
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