Microwindows on Icecube/CoralP

Wolfgang Denk wd at denx.de
Tue Feb 8 06:55:15 EST 2005

Dear Francois,

in message <IBJDLO$2F7CB4091C41824099E5E47AB0570FD3 at tiscali.fr> you wrote:
> I have been playing with the CoralP, Icecube and Debian.
> Works fine, thanks to the tutorial on the Denx site.
> I now would like to see the microwindows stuff working. I

This will not work. Microwindows can only  use  a  plain  framebuffer
interface,  but  the Coral-P does not allow for such a driver because
of the fact that it has a little-endian register interface.  For  the
frameboffer,  each color is defined by a bit offset and the number of
(contiguous bits) in a data word. For example, assuming a color depth
of 16 bpp you could have something like this:

	MSB          LSB

In this case the "green" color has bit offset 5 and is 5  bits  wide,
while  "red" has offset 10 and is 6 bits wide. On the Coral-P you see
the bytes swapped, i. e.

	MSB          LSB

The "green" bits are  split  into  two  non-contiguous  groups  which
cannot  be  desribed  in  the  way  it  is  needed  for a framebuffer

You will need a custom graphics driver which  swaps  all  color  data
that  get  written  to  the  Coral-P.  Standard Microwindows does not
support this mode of operation.

> have been trying the demos from the ELDK but I get strange
> colors, it seems my palette is all wrong. The same happens

Yes, this is the effect explained above.

> when I recompile the latest version of microwindows (except
> I get yet another palette).

Again, thisis only to be expected.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"Here's a fish hangs in the net like a poor man's right in  the  law.
'Twill hardly come out."     - Shakespeare, Pericles, Act II, Scene 1

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