David W Hogg wrote:
Perhaps this is a question for hardware folks, not devel folks, but
could someone out there tell me if the reflective, b/w mode for the
monitor will be 8-bit greyscale or 1-bit on-off pixels? I am writing
an application for the laptop, but it is *essential* that it run
completely in the reflective mode if that is possible; I need to know
if I can use "greys" or only strict "black" and "white".
It is greyscale, but not a simple 8 bit-per-pixel mode. I don't
completely understand all the details, but I do know that if you are in
monochrome mode and you write color values of different luminance, you
see different shades of gray. For example, you can generate a
monotonically increasing brightness ramp as follows:
a) Set the display controller to RGB565 mode (the mode that we use in
most cases)
b) With the R and B components set to 0, increment G from 0 to 63
c) With G at 63, increment B from 0 to 31
d) With G at 63 and B at 31, increment R from 0 to 31.
That gives you 128 distinct grays, which my eye can distinguish for the
most part (although the darkest 10 or so look essentially black to me).
I presume that one could improve on that by using more subtle combinations.
Also, are there *software* handles for the reflective vs transmissive
modes, or is that always controlled by hardware and/or the user?
Both the backlight and the color/monochrome modes can be controlled in
software.
You can convince yourself of all these assertions with simple tests from
the firmware (it helps to use a recent firmware release like
http://wiki.laptop.org/go/OLPC_Firmware_Q2B61 , because the logo in
versions Q2B34 and later is multicolored, so it shows the different
shades of gray).
ok stdout @ iselect
ok 0 set-color
ok 0 bright!
The "set-color" command goes into monochrome mode, while the "bright!"
command turns the backlight all the way down.
There are ways to do this from Linux, but I don't have the details handy.
Thanks very much in advance for any help you can give.
Hogg
ps. If you want to know *why* I need to work in the reflective mode:
my application is for backyard/schoolyard astronomy and we must
maintain dark adaptation. See
http://howdy.physics.nyu.edu/index.php/OLPC_planetarium
pps. Hey you Media Lab types: I was Lego Lab 1989-1992.
_______________________________________________
Devel mailing list
[email protected]
http://mailman.laptop.org/mailman/listinfo/devel
