[sane-devel] Weirdness with Canon FS2720U

Tabor Kelly tkelly-sane-devel at taborandtashell.net
Thu Aug 3 19:07:42 UTC 2006

m. Allan Noah wrote:
> sometimes you write a stupid loop and you dont wory about it. othertimes 
> it is trying to reserve all the LUNs. with the fujitsu's, i just leave 
> those two commands out, and it works. (there is only one master on the 
> USB anyway)

Well, in the part I was talking about they reserved LUN = 0 eleven 
times. I just used to work as a software quality assurance engineer and 
this sort of thing is like fingernails on a blackboard to me. Maybe it 
is a personal problem :-)'.

> opcode 0x2a, data type code 3 == send gamma table, in this case 10 bits.
> notice bytes 4 & 5 of the command before the table are 00 00, then 00 
> 01, then 00 02 ... those are the 'id' of the table being loaded. later, 
> in the set window command, that id will be used to tell the scanner how 
> to munge the scan. these default ramps are linear, you may be able to 
> leave them out.

Thanks for catching this, I was reading the SCSI spec wrong and thinking 
it was the WRITE opcode (also 2Ah). This makes a lot more sense now.

>> 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?
> have you tried just adding usb support to the existing canon scsi backend?

Not yet, I will probably do that eventually. Right now I just want to 
get data back on a *nix box.

Thanks Again,

Tabor Kelly

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