[sane-devel] How to read scan count (hp5590)?

[Ilia Sotnikov]

On Wed, Jun 13, 2012 at 5:17 PM, Matti Viljanen
<matti.viljanen at wippies.com> wrote:
> Hi,
>
> For a few days I've tried to extend scanbuttond to include also the value
> that's displayed in the little LCD panel in my HP ScanJet 5590
> (by making scanbuttond run the script with one more arg). Does anyone know
> how it's supposed to be read?

Hi, Matti!
As far as I understand, the LCD isn't controlled by device driver or
backend, rather the controller/firmware simply reacts on Up/Down
buttons press and increments/decrements the value displayed. So, you
need to handle button press events and store the resulting value.

> According to sane backend 'hp5590' source, the devices EEPROM must be read.
> Comparing with reading button status, how different an operation this is?
> All I get is usbfs error lines (ret -110 --> timeout) although I believe the
> code is identical...
> Has anyone actually gotten the value out correctly?

Well, there is a function to read all EEPROM from the device (see
backends/hp5590_read_eeprom_all_cmd.c from SANE sources) - might be an
interesting idea to read the contents upon receiving an event from
buttons, we might find something being stored there. My wild guess is
that LCD connected to a GPIO of controller and firmware just handles
it internally. Unfortunately, original Windows driver has shown
nothing (or I didn't notice) revealing any interface to that.

-- 
 Ilia Sotnikov