[sane-devel] Re: HP 4570c - any progress?

[Bertrik Sikken]

Henning Meier-Geinitz wrote:
> Hi,
>
> On Tue, Sep 13, 2005 at 07:36:19PM +0200, Bertrik Sikken wrote:
>
>>The protocol is weird because it seems to implement some kind of
>>'USB-over-USB', i.e. the data payload of the USB control packets
>>looks like another USB control packet. The payload size never
>>appears to exceed 8 bytes.
>
>
> Maybe this is one of the scanners which use a GL660 as a USB2.0 chip
> and the GL646 (USB 1.1) as the real scan chip? This could explain the
> USB-over-USB protocol.

Ok, that would explain a lot, but why would they do that?
I don't think there is a GL646 chip in the scanner.

The more I look at the usbsnoopy log, the more it looks similar
to the hp5400 backend. This is probably good news because the
hp5400 accepts a limited set of commands instead of dozens of
writes to various registers.

BTW, Daniel, I wrote a simple command line tool that talks to a
hp5400 to query it for its version string. This can be useful
as an example to do some low-level debugging in the early stages
of hacking. You still need to modify it to use the USB-over-USB
protocol, though, but I can help you with that.

Kind regards,
Bertrik