[sane-devel] CanoScan N1240U is working with plustek backend

[Gerhard Jaeger]

Hi Johann,

great to her from you!
First of all the whole backend is based on code I got from
Plustek, therefore it's sometimes not really clear what they've
done. Esp. the differences between the originally supported devices
are "hardcoded" by using CCD-type, PCD-id and motor type...

Anyway. Calibration is a problem for me so far, as this does not really
work for correctly for my 670 here. We might have to write new routines
for the CIS devices. 

Before you continue, I suggest to use at least the 0.45-TEST2 version
from www.g-jaeger.de/scanner/plustek.html. This one provides a better
picture quality on the CanoScan devices even without calibration...

Your questions:

On Sonntag, 17. November 2002 16:58, Johann Philipp wrote:
> Hi
>
> I'm happy to post a definitely positive message: My CanoScan N1240U is
> working with the plustek backend. Some details:
> Scanner is a LM9833 based CIS type with 1200x2400dpi @ 48bit color depth,
> Sane is version 1.0.9 taken from cvs yesterday,
> adaptions were made only to plustek-devs.c and plustek.conf.
> Great work, Gerhard! I have been working on a CanoScan backend within the
> canonscanner project on sourceforge.net and were able to scan with it too.
> But your version is much more flexible and stable.
> I need to test some more on all the hardware settings, before I will
> provide you with a "non-dangerous" patch for the N1240U. Also I hope to get
> the calibration working, but there are a few questions open:
>
> 1) Basically the routines seem to work, but I need some more control on the
> Y-positions / sizes of the white and black part of the calibration strip.
> As far as I have seen, I cannot control this completely in plustek.conf.
> Can you give some help, where and for what to start looking?

The X/Y positions of the strip can be set in plustek-devs.c at the DCapsDef
entry, the size is currently fixed inside the calibration routines to the
width of the scanbed - see the four main calibration routines:
coarse calibration:
usb_AdjustGain()
usb_AdjustOffset()
fine calibration:
usb_AdjustDarkShading()
usb_AdjustWhiteShading()

At least the fine calibration is not yet activated as I have too much
trouble with it (disabled by the flag WAF_SKIP_FINE in DCapsDef
entry of the device...
For debugging the output of the calibration data, you might set
the debug-level of the backend to 20 and you'll get a bunch of
*.raw files...


> 2) What for do you need the "black optical pixels" (regs 0x1c and 0x1d)
> during calibration? Sniffed data says that my windows driver software never
> uses these during calibration.

Hmpf - good question! I thought I got those settings from the various
test-programs around, but nope! Well in fact I guess those are settings
from another scanner so far. They're used in function usb_AdjustOffset()
but aren't of much use so far...

I'd be happy if you can manage to provide some kind of calibration code
for this scanner type...

>
> Greetings
> Johann

Cheers
  Gerhard

BTW: I assume, that you're talking german and we might continue
in a private discussion...