[sane-devel] Re: How to link the Scan Button of CX3100 to a linux application?

[m. allan noah]

On Tue, 27 Jan 2004, Bruce Bertrand wrote:

> Till Kamppeter wrote:
> 
> > I recommend that you post this on the SANE mailing list 
> > (http://www.sane-project.org/), as this is a scanning problem. I am 
> > CCing this posting to there.
> >
> > AFAIK noone has written a driver for scanner buttons yet (also not for 
> > other scanner models). The scanner probably sends a certain signal 
> > through the USB which is caught by a background process under Windows. 
> > This process then starts a program to do the scan. The best way to 
> > write a similar program under Linux is to use a USB sniffer to analyze 
> > how the signal looks like and then write a daemon which listens for 
> > such signals.
> >
> >    Till
> 
> If this is the case, then it would only take one sniffer for all 
> scanners that operate in this manner. Sort of like those universal 
> "learning" remotes, where you hold up an existing remote to the learning 
> remote, hit a "listen" button and then press a button on the old one, 
> assigning whatever signal it receives to some function on the learning 
> remote.
> Bruce

not so simple as that. for machines with adf, you will usually have a 
couple other sensors like paper thickness, input or output hopper 
empty/full, cover open, lamp warm, etc. if the scanner sends all those as 
a bitmask in one packet, then the user doing a button-press might show up 
as a dozen different codes, based on those other flags. your 'generic' 
button monitor would have to know a whole lot more about each individual 
model than you would want (esp when things like which usb endpoint to use 
and bulk v/s interrupt are taken into account)

all-in-all this sort of thing (reading the raw output from the scanner) 
belongs in the backend, with suitable abstraction that a frontend could 
use. finding that abstraction is more problematic...

allan

> 
> 

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