View Full Version : 80 column, 24 row text driver for 640x480 vga?

05-12-2008, 05:38 AM
Is there a driver for this?
Seems like it should be possible...

Peter Jakacki
05-12-2008, 06:05 AM
The VGA High-Res Text Driver has a 80x40 VGA mode. If you really only want 24 lines then you could either limit the text area or increase the line spacing. Other than that you would have to define a font different from the 8x12 that would allow you to stretch across the lines better.


05-12-2008, 09:59 AM
I have been thinking such a thing for some time, but haven't had a chance to unravel VGA_HIRES_TEXT. It would require an 8x16 font (for 640x480), and the two cogs would each be loaded with half the lines of the font. It may even be possible to get it down to one cog by using an 8x8 font and line doubling. I have bitmaps of a high-readability font in 8x8 and 8x16 squirreled away somewhere which may be useful.

05-12-2008, 06:03 PM
I think the 1 cog and double buffering sounds better... I think it'd be useful if you could do it. I just want it for my Ladder game :)

05-12-2008, 10:18 PM
There was a thread about how to scale down the bitmap fonts by using only certain rows and columns.
The results looks pretty good if I remember correctly.
Maybe you can find that post, it would allow you to display a 8x16 font created from the built-in font table.


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05-13-2008, 01:36 AM
The scale down of the parallax font is almost great, some letters have one vertical line like the F and some double like the T, but is very readable. You only need a small trick to recover it using some SHR/ROL combinations you can easily extract the right char something like:

extract even:
rdlong temp,ptr_to_font
mov cnt,#8
shl temp,#1 wc
shl temp,#3
rol dest,#1
djnz cnt,#lbl1

to get the odd just add a initial shl after the label lbl1, but you knew that http://forums.parallax.com/images/smilies/smile.gif
and skip every other line, too.