[sane-devel] hp 7650 hangs at higher res, inter alia

[Ilia Sotnikov]

On Thu, May 20, 2010 at 3:28 AM, Michael J Eurice
<mike.eurice at verizon.net> wrote:
...
> I am able to scan color and mono and scan multipage documents up to a resolution of
> 300dpi, but above that the scanner hangs part of the way through the first page.
...

Hello, Michael!

I've seen several hangs when I even forced to switch off the device
(unplug power cord) only while backend development.
Did you experience the same hard lockup? Or the device starts normally
when you start over?

...
> Another issue, which I worked around, was that the units were in
> inches but the digits were the corresponding centimeter value;
...

I didn't test inch measurements thoroughly, to be honest. Internally
the backend is millimeter centric.

...
> I forced the size to 8.5 x 11 inches and sorted out that issue. Now the scanner captures
> all of the first page and about 0.3 inches of the second page, producing a
> cumulative page content error for all subsequent pages.  I set the page
> length to 10.700 inches to work around that issue, but any residual error
> will grow to the point of being a problem for larger documents.  It seems as
> though sane is not looking for the end of the page, and I believe that
> detection capability exists in this hp device.
...

I found no paper sensor related commands while reverse engineering the
original Windows driver. I suppose that original driver does
some kind of paper length detection (or I did miss some major parts of
device protocol). At the moment, SANE backend just uses the page
length which is set by user. Thus, you did the best you can - adjusted
the length yourself.

...
> It also seems like I am violating some page or file size limit when I raise the scan resolution, but
> my search turned up no reference to such a configuration parameter.
...

There is no configuration file for the backend at all, so you did miss
nothing related to that.
Regarding the size limits - the backend uses just a small buffer
(about 64K), so the possibility that you experienced some memory
issues is rather low. You could try to scan using different frontend.

...
> The sane website reports this scanner as status "complete" and describes the
> device in the hp5590 manpage: ScanJet 7650, USB, 0x03f0/0x1805, Complete,
> Lineart/grayscale/color (24 bit), 100/200/300/600/1200/2400 DPI,
> flatbed/ADF/ADF duplex/TMA slides/TMA negatives, hp5590 (1.0.5),
> sane-hp5590.
...

It is marked 'complete' because main functionality is rather stable
(in my opinion).

...
> Is there another backend that better supports the hp 7650?
...

Several years ago HP sent me binary only SANE backend which was marked
as unofficial. I couldn't provide it due to the agreement.

Feel free to ask me,
-- 
 Ilia Sotnikov