[sane-devel] HP scanjet 2400

[Stéphane VOLTZ]

	Hello,

	there was a patch (by Luke) recently that allowed warming up to work for the 
HP2400. The following function in execution path to fix is 
gl646_search_start_position() .  A way to do it is to run the backend with 
all the debug, and compare this output with what it does under windows. Then 
correct the function until the picture scanned to locate the start of 
scanning area matches the one from windows USB log.
	From time to time I upgrade the document at 
http://stef.dev.free.fr/sane/genesys with informations on the genesys backend 
and how to modify it. It explains also how to work with windows USB logs. 
	The next major hurdle one has to overcome for the 2400 if the creation of the 
slope tables that drive the stepper motor. The HP2300 and MD6471 code uses 
an 'old' method with some magic constants to generate slope tables matching 
those in logs, but gl841 based scanners code uses a newer and better function 
that is based on the start and cruise speed needed.
	There must also be some register tweaking to do, but this is easy (places 
testing for a HP2300 will give you hints) to do with a simple compare to 
windows log.

Regards,
	Stef