[sane-devel] "first light" with CanoScan LiDE 600F

Jürgen Ernst jrernst at gmx.de
Fri Jan 11 14:02:48 UTC 2008

stef wrote:
> 	Hello,
> 	surely be some timing issue. When reading data, especially scanned data, you 
> sometime have to wait for it being available before reading it. USB logs 
> don't have a timestamp, which hide all possible idle waits.
> 	Sometimes there is a read before that gives the available data count.

No that's not possible.

a) I accessed the scanner with a perl script. It's much slower than C.

b) I sent the data from the log which was a bulk of 512 bytes. This 
gives additional delay. Maybe it's therefore a 512 byte block to slow it 
down a bit when accessing it at full speed.

c) I used benoit's usbsnoop and the log HAS timestamps shown in 
milliseconds. The delay time in log is below 1 ms.

d) NO read is shown before in the log with data count. The data count is 
always 1 with that request.

You can have a look at the logs at 
First bulk_write is at URB 7. Return value is 0x81.


Microsoft is not the answer. Microsoft is the question.
"NO" is the answer.

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