primax: Thread: D600 Users README

Readme file for D600 Users
==========================

Mike Rothon ####@####.####

V0.01 16/03/03


Introduction
------------

First the good news...

It is possible to use the Primax Colorado D600/30 bit scanner with Linux! 
However its use is limited at the current time and there are some changes to 
the driver that need to be made before you can use it at all.


Limitations
-----------

Generally the scans can only be made at 300 dpi. This is going to be the 
hardest problem to solve as it would seem that the similarities between the 
D300 (for which the driver was originally written) and the D600 seem to end 
at resolutions above 300 dpi.

The full page cannot be scanned. If you try this the scanner will lock up at 
the end of the page. This is a problem when using Kooka as it tries to first 
make a preview scan of the whole page to display in the preview window. The 
problem is probably caused by rounding and should be relatively simple to fix 
- watch this space.

Software Modifications
----------------------

In order to be able to use the D600 at all you will need to make the following
modifications. This list is based on the driver version primaxscan-1.1beta1.

In file tables.c:

int RESOLUTION = 300;    /* [dpi] */

becomes

int RESOLUTION = 600;    /* [dpi] */


In file LM9811.c

calibration_image->resolution = X_RESOLUTION;

becomes

calibration_image->resolution = X_RESOLUTION / 2; (see note 1)


In file tables.h

#define RED_OFFSET = (0 * RESOLUTION * COLOR_SPACING);
#define GREEN_OFFSET = (1 * RESOLUTION * COLOR_SPACING);
#define BLUE_OFFSET = (2 * RESOLUTION * COLOR_SPACING);

become

#define RED_OFFSET     (0)
#define GREEN_OFFSET   (3)
#define BLUE_OFFSET    (7) (see note 2)


Notes
-----

1. The reason why the calibration scan resolution needs to be half the 
scanners maximum resolution is that currently the driver locks up at 
resolutions greater than 300 dpi if the whole page width is scanned.

The reason for this is not yet known, but is possibly because the ASIC 
behaviour in the D600 was modified from the D300 for scan resolutions above 
300 dpi.

2. It seems that the three guns in the D600 CCT are closer together than in 
the D300. This would make sense given the Primax claim of 1200 dpi in the Y 
direction (i.e. color spacing is one quarter or 1 / 300 inch). I picked the 
values above as they give the best results with my scanner - you can see the 
difference by scanning some black on white text with the original values and 
then with these. There is significantly less fringing and black is really 
black!!

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Great!

This is really cool. I added the file to the CVS ( README.D600 ) so it is 
plublic available and other developers can use it. 

As your earlier posting about CVS I wonder if you could add your stuff to the 
CVS code base. Just add some IFs. So we could release a version that works 
with the D600.

Gruss,

Andre
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