ubb-vga "double" mode (was Re: Ben + UBB + a few components = "VGA")

Werner Almesberger werner at almesberger.net
Sun Apr 24 23:19:28 EDT 2011


I wrote:
> Yeah, I wonder how much we can strecth those timings. At least in
> theory, a digital display doesn't really need a lower bound for
> pixel frequency and such. So maybe even a better approximation of
> full QVGA resolution is possible.

ubb-vga now has a "double" mode in which it uses a set/clear pair
for each pixel instead of alternating set and clear. This improves
the resolution but makes the timing quite VGA-unlike.

Single:
http://downloads.qi-hardware.com/people/werner/ubb/vga/ubb-vga-screenshot.jpg

Double:
http://downloads.qi-hardware.com/people/werner/ubb/vga/ubb-vga-double.jpg

For reference, the original screen content is here:
http://downloads.qi-hardware.com/people/werner/ubb/vga/jlime-desktop-original.png

One can see that about five pixels get chopped off the left and
about 25 pixels off the right. I've tried this only with one
monitor so far and don't know yet how palatable others will find
this signal.

For those interested in how the mappings work, here's a diagram:
http://downloads.qi-hardware.com/people/werner/ubb/vga/mapping.pdf

And here's the description (section "Single/double mode"):
http://projects.qi-hardware.com/index.php/p/ben-blinkenlights/source/tree/master/ubb-vga/README

Last but not least, Wolfgang has made a better conversion of my
ubb-vga video (uncut):

http://en.qi-hardware.com/w/images/7/76/Ben_UBB_VGA.ogv

Thanks !

- Werner




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