[sane-devel] Weirdness with Canon FS2720U

Tabor Kelly tkelly-sane-devel at taborandtashell.net
Thu Aug 3 04:05:45 UTC 2006

I now have a Trac site (with associated subversion repository) setup at 
my University (https://projects.cecs.pdx.edu/~kellyt/SANE-FS2720U). I 
have text files in the repository that is browsable here 
that explain in English what is going on with the scanner. There are 
things I find odd, like executing the RESERVE UNIT or RELEASE UNIT 
command over and over again. When you change the film type it is 
particularly amusing: it calls RESERVE UNIT 11 times (and that is all it 
doesn, it doesn't send any command to acutally change the film type).

Is this at all normal? I assume it just borked commercial software.

What I would love for someone to take a look at is URB 289-300 in this 
  It looks like the windows driver writes 24kB of data to the scanner. 
But look at the data, it isn't firmware, it is a pretty pattern. Any 
idea? Was the developer who wrote this driver just having a little fun 
at my expense?

I think next I am going to write some libusb code (my first) and try 
cutting out some of these steps. The scanner has flash memory on the 
mainboard, I don't understand why it would need its firmware upgraded 
every time. Maybe Canon didn't build in a facility to actually upgrade 
the firmware and they are writing over active memory every time you turn 
it on?



PS- My entire project is availabe for checkout from the subversions 
repository at https://projects.cecs.pdx.edu/svn/SANE-FS2720U/.

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