[sane-devel] HP 8250 ADF doesn't work (patch)

Mon Sep 13 14:14:58 UTC 2010

Mike,

THIS IS GREAT!  I have a couple of HP8250 scanners, and can do some
testing.  The next week or two I am buried, but I can go after it late this
month.  Besides the weather gets cold and rainy then.

I'll look through your stuff, and make sure I understand it, etc.

Also, I'm willing to work with anyone else going after this.  The 8250 is a
nice inexpensive sheet feed scanner, and it would be great to have fuller
functionality using xsane.

Val

ps: What I do currently is use a windoze machine running the HP software to
reset the scanner, then I can usually scan without problem until a paperjam
or power failure.  Then I plug the scanner into the old laptop and do a
reset, and then back to the linux box doing the scan.  That allows me to do
ADF, but does not allow me to do duplex, for example. (obviously)

On Mon, Sep 13, 2010 at 9:15 AM, Mike Kelly <mike at piratehaven.org> wrote:

> Hi,
>
> I own an HP 8250 scanner, but the ADF unit doesn't work with sane.  In my
> attempt to find a solution I stumbled upon Debian bug 521410
> (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521410).  In this bug,
> it
> is reported that scanning used to work with a previous version of
> avision.c,
> but that with later versions the ADF stopped working.  With the supplied
> log
> files in that bug, I decided to try to figure out what changed in the
> source
> and see if I could return the functionality.
>
> I went through every change in avision.c, going back until June of 2006,
> until I narrowed the problem down to a bit field which used to have one of
> two bits set for all ADF scanners but was later changed to only set the
> bits
> based on ADF capabilities.  Unfortunately the new code which determines the
> ADF's capabilities excludes this scanner.
>
> There are two core problems:
> 1) The first is that the code is trying to determine the ADF model from the
>   scanner, but the returned value from the scanner is not giving us enough
>   information to determine what the capabilities are for the ADF.
> 2) The second is that the code added to correctly set the scanner bits for
>   2-pass duplex scanners sets a completely different set of bits than
>   before.
>
> About the first problem (detecting the ADF):
>
> The code uses a byte value returned from the scanner labeled "adf_model" in
> the source, but the returned value is a value in the range of 0 to 2.
> Although the code assigns model names to these values, it seems that
> different scanners, with clearly different ADF units, return the same model
> number, so the names can't possibly be valid.  How HP uses this byte is
> unclear, but I suspect that if it is used at all, there is a lookup table
> to
> determine the ADF features based on the scanner model.  I've looked at
> debug
> logs for almost all of the supported scanners to support this conclusion.
>
> In fact, having reviewed the documentation of each supported model and its
> ADF capabilities, I have concluded that this byte can be safely ignored,
> and that knowing the base scanner model is sufficient.  I implemented a
> simple flag, AV_ADF_SUPPORTS_DUPLEX, which I have applied to the scanner
> models which support duplex scanning.  If I can believe the comments, this
> change only affects HP scanners.
>
> About the second problem (setting the correct bits):
>
> The original code, for all ADF scanners, set either the duplex (0x10) or
> rear scanner bits (0x08) depending on the selected ADF mode.  The
> subsequent
> changes do this for only interlaced scanners (aka 1-pass scanners).  The
> code does not set these bits for 2-pass scanners, but instead sets the
> lowest three bits (0x07) of the bitset3 bit field.
>
> The comments suggest that only HP scanners do 2-pass scanning, so I haven't
> looked at other Avision scanners.  In the 2-pass case, the last three bits
> are set, but the duplex mode (0x10) is not.  The comments in the code do
> not
> lead me to believe that the rear scanning mode exists for HP equipment,
> neither do the photos, debug logs, or documentation of the equipment.  As a
> result, my change is to add setting of the duplex bit (0x10) in addition to
> the last three bits (0x07) (although it should be noted that these were not
> originally set).  I also changed the setting of the bit fields to use the
> SET_BIT macro which seems to be the preferred way to toggle bits.
>
>
> While I was patching the code, I decided to clean up some clever, but
> confusing, code in the set_window() function.  I replaced an intermediate
> value (adf_mode) with references to the underlying core data structure
> (s->source_mode).  This change looks bigger than it is because of I had to
> fix the indenting.
>
>
> Now for the bad news.  I have not tested this code at all.  Unfortunately,
> my scanner is inaccessible to me for the next year, as I've moved overseas
> temporarily.  I can only assume it would work based on the debugging output
> in the aforementioned bug.  I realize it's kind of rude to just dump
> untested code on the group, but I hope you will forgive me as I don't
> actually have the hardware in my possession at the moment.
>
> I've put in a lot of effort to avoid breaking other scanners, but I can't
> be
> 100% sure that I've been successful.  HP scanners older than the 8200
> series
> should be unaffected by these changes, as they don't support duplexing and
> don't enter these code paths.  However, I'm worried about the 8300 series
> scanners because I have not been able to find a debug log for them.  This
> implies that they are working with the current code, but without a debug
> log, I can't know which code path they use.
>
> So, if possible, please test this patch if you have a ScanJet 8200 series
> scanner with an ADF unit.  If you're an owner of a ScanJet 8300 series
> scanner with an ADF unit, please send me a debug log (patch or not).
>
> These are the avision supported HP duplex capable scanners:
> HP ScanJet 8200  (This model didn't ship with an ADF)
> HP ScanJet 8250  (15ppm 2-pass)
> HP ScanJet 8290  (25ppm 2-pass)
> HP ScanJet 8270  (25ppm 2-pass, replaces the 8290)
> HP ScanJet 8300  (This model didn't ship with an ADF)
> HP ScanJet 8350  (25ppm 1-pass)
> HP ScanJet 8390  (35ppm 1-pass)
>
> Thanks,
>
> Mike
> (:
>
> --
>
> --------Mike at PirateHaven.org-----------------------The_glass_is_too_big--------
>
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