pete hilton <saruman@ruvolo-hilton.org> wrote:

> Having got netbsd working satisfactorily on my Z50, I have been
> looking into how to control the brightness/contrast on the LCD.
>
> Having looked at the ITE8181 specs that I have and the VR4171
> chipset specs I cannot see any registers which would allow anything
> other than backlight on or off.  Obviously there is SOME way to
> handle brightness/contrast because WINCE does it, but does anyone
> know (or have a pointer to) how this works.  I dont care about the
> buttons on the LCD panel because we can always use an ioctl or some
> such once we know what the hardware mechanism is and how it is
> accessed.
>
> If there is anyone from IBM out there watching this group who has a
> detailed schematic or programming spec for the Z50, it would be very
> nice to hear from them:-)) ... my guess in all this is that there is
> another control on the LCD that is not documented publicly which
> handles the brightness/contrast.

One strategy might be to disassemble the WinCE ROM and stare at it for
a while.

Another (a complementary one) - is to make the bootloader or kernel
dump contents of all "interesting" hw registers at the boot time and
then boot repeatedly with different brightness/contrast settings and
watch for changed values.

PS: I had to do just that for hpcsh Jornadas to discover that
brightness is controlled via DAC, and contrast via GPIO pins.

SY, Uwe
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