[sane-devel] gunt

Gerald Murray gmurray at cloudnet.com
Thu Mar 23 00:25:43 UTC 2006

Quoting Nehpets Farnkiln <plamtrue at yahoo.com>:

> So I'm working on a project wherein I've removed the CCD and stepper motor
> from the case, and have it mounted elsewhere. 
>   I'm looking to get the image data from the scanner one scanline at a  time
> (rather than the entirety of all the scanlines at once), and I'm  also
> looking to make the scanner keep scanning until I signal it to  stop (rather
> than returning the carriage back it's starting point after  11 inches or
> whatever).  But I'm fairly pathetic in my programming  skills.  Are the
> backends capable of doing these things?
>   -Stephen Franklin

Hi Stephen,
Your question is quite general.  The answer is more dependent upon the
scanner and its firmware/interfaces.  Inside the scanner is some kind 
of a processor with its instruction/register set.  Some scanners are capable
of doing what you want; others are not.  For those that are not capable of
that, the scanner receives all the parameters.  At the point where the 
scan starts, the backend no longer has any control until all of the image
bytes have been transfered.  Then the backend can regain control, and 
ask if the bytes sent are the exact number of the bytes expected.  If yes,
the scan succeeded; else it failed.  When the command to scan is sent,
that scanner has in its program a shuffle.   When the scanner cannot
send more bytes because the buffer is already full, the scanner then does
its shuffle until the buffer has the room to accomidate.  Upon completion
of the image transfer, the head is sent home.  
You will need to customize the backend and then test to do your agenda.

Good luck,

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