.TH sane-scsi 5 "16 Aug 2001"
.IX sane-usb
.SH NAME
sane-usb - USB configuration tips for SANE
.SH DESCRIPTION
This manual page contains tips and tricks on how to access scanners
with a USB interface.
.SH GENERAL INFO
Sane-backends currently use three methods of communicating with USB scanners: 
.TP 2
- 
Using libusb (a library for usb access). This is used by the sm3600 backend
currently.
.TP
- 
Access through sanei_usb, the SANE USB interface. Used by the mustek_usb
backend.
.TP
- 
Direct access to the USB device files to access kernel scanner drivers
.PP
This manual page describes the access of USB scanners over the sanei_usb
interface. For point 1 and three of this list have a look at the backend's
manual page for details.
.PP
Currently USB access is only tested for Linux and FreeBSD.
.PP
For scanners with a USB interface, it may be necessary to edit the
appropriate backend configuration file before using SANE for the first time.
For most systems, the configuration file should list the name of the USB
device file that the scanner is connected to (e.g., under Linux,
.B /dev/usb/scanner0
or
.B /dev/usbscanner0
is such a USB device, the device file for FreeBSD is e.g.
.BR /dev/uscanner0 ).
Do
.I not
create a symlink from
.B /dev/scanner
to the USB device because this link is used by the SCSI backends. The scanner
may be confused if it receives SCSI commands.  For a detailed description of
each backend's configuration file, please refer to the relevant backend manual
page (e.g. sane-mustek_usb Mustek USB scanners).
.PP
For Linux, there is an alternate way of specifying scanner devices.  This
alternate allows to identify scanners by the USB vendor and product numbers.
The syntax for specifying a scanner in this way is:
.PP
.RS
usb
.I VENDOR PRODUCT
.RE
.PP
where
.I VENDOR
is the USB vendor id, and
.I PRODUCT
is the USB product id of the scanner. Both ids are non-negative integer
numbers in decimal or hexadecimal format. The correct values for these fields
can be found by looking at the output of the command "cat
/proc/bus/usb/devices/".  This is an example of a config file line:
.PP
.RS
usb 0x055f 0x0006
.RE
.PP
would have the effect that all USB devices in the system with a vendor id of
0x55f and a product id of 0x0006 would be probed and recognized by the
backend. The same config line in decimal format looks like this:
.PP
.RS
usb 0x055f 0x0006
.RE
.PP
When using a USB scanner, ensure that the access permission for the
USB device is set appropriately.  We recommend to add a group
"scanner" to /etc/group which contains all users that should have
access to the scanner.  The permission of the device should then be
set to allow group read and write access.  For example, if the scanner
is at USB device
.BR /dev/usb/scanner0 ,
then the following two commands would set the permission correctly:
.PP
.RS
$ chgrp scanner /dev/usb/scanner0
.br
$ chmod 660 /dev/usb/scanner0
.SH ENVIRONMENT
.TP
.B SANE_DEBUG_SANEI_USB
If the library was compiled with debug support enabled, this
environment variable controls the debug level for the USB I/O
subsystem.  E.g., a value of 128 requests all debug output to be
printed.  Smaller levels reduce verbosity.
.SH "SEE ALSO"
sane(7), sane\-find\-scanner(1), sane\-"backendname"(5), sane-scsi(5)
.SH AUTHOR
Henning Meier-Geinitz. Some parts were copied from the sane-scsi manual page.