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

Ilia Sotnikov hostcc at gmail.com
Fri May 28 12:09:26 UTC 2010

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

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