[sane-devel] Ideas Wanted [Acer ScanWit]

[Oliver Schwartz]

Hi Max,

> I am still playing with Acer ScanWit 2720S film scanner and I
> found out some protocol details that allow me to scan. I am
> about to start writing a quite restricted SANE backend for this
> thing. 

From your description it looks as if the protocol of the Scanwit is close to 
Status: O

the Agfa/Acer flatbed protocol. Maybe it makes sense to modify the Snapscan 
backend instead of writing a new backend (see 
http://snapscan.sourceforge.net).

>    READ with DT=0x80 and DTQ=0, 61056 bytes
>    READ with DT=0x80 and DTQ=0, 0 bytes

According to the Agfa Specs that I have, DT=0x80 is "Measure Transfer Time". 
It's used to synchronize the speed of the scanner with the speed of the data 
processing on the target machine, so that the scanner does not have to stop 
in the middle of the scan because a slow target machine cannot process the 
data fast enough. There is a detailed explanation on how this command should 
be executed in the docs. The Snapscan backend has a working implementation.

>    READ with DT=0x82 and DTQ=0x10, 7650 bytes
>    (repeats 15 times)
>    SEND with DT=0x82 and DTQ=0x01, 7650 bytes

DT=0x82 is "Shading Data" - as guessed before, thats the data from the 
calibration process. Again, there's an implementation in the Snapscan backend.

I'll send you the Agfa spec in a separate email as it's a larger document.

Regards,

Oliver