plustek: CanoScan N650U
Subject:
Re: CanoScan N650U
From:
"Stephen W. Nuchia" ####@####.####
Date:
8 Jul 2002 14:38:58 -0000
Message-Id: <Pine.GSO.4.40.0207080906300.3750-100000@l1asun1>
Further info on my N650U adventure:
The speed calculations are broken, too. Watching it work with
the lid open I make the following observations:
At very high scanning density, the head moves most of the way down
the page. At medium densitiies it moves about halfway, and at very
low densities it sits at the start point vibraring.
Changing the speed limit in the hardware description structure
(from 0.7 ips to 0.1 ips) seems to work for the lights-off motion
but does not limit the scanning speed.
Not knowing the encoding for the register that is marked as
acceleration ramp, I just played with it a little but it didn't
seem to improve anything.
Reading plustek-usbscan.c, it appears that the proper speed calculation
code is #if 0'd out. What is in effect is labeled "poor man's
calculation" and does not incorporate the speed limit.
My conclusion: the stepper is being overdriven, and the acceleration
ramp parameter is probably not optimal. The kickstart parameter may
be wrong too. Hard to tell without putting the thing on a bench and
skinning it.
Based on your statement that the data read code isn't ready, I'm
going to requisition another scanner. I'd still like to get this
one working at home, though.
