The correct special device file has to be created prior to using it with Sane. See the USB documentation for more information about how to set up the USB subsystem and the required device files. The static library implementing this backend. If the library was compiled with debug support enabled, this environment variable controls the debug level for this backend. E.g., a value of 128 requests all debug output to be printed.
Smaller levels reduce verbosity.
This allows to override the function or command level that the backend uses to communicate with the scanner. If the backend does not recognize the function level reported by the scanner it will default to function level B5. Valid function levels are A1, A2, B1, B2, B3, B4, B5, B6, B7, B8 and F5. At least none are currently known. The backend may be used with Epson scanners that are not yet listed under the list of supported devices.