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Re: Apple ][ to VGA monitor adapter board - looking for best color decoding method

sicklittlemonkey wrote:

On Apr 9, 7:32 am, ferd...@gmx.de wrote:


Hi all!

With the understanding of the decoder circuit (I got the schematics
from Marcus Heuser - thank you!)
I was able to optimize color displays. The principle of the Shift
register/latch circuit delivers a very poor picture if a different
resistor network is connected to get RGB output. This was unusable, my
method was far better. But, based on the resistor network  of the PAL
color card, I was able to recalculate my values and got to this:http://img87.imageshack.us/my.php?image=comparisonau3.jpg
The lower monitor is a 14'' NTSC device connected to the video out,
the upper monitor is a 12'' IBM VGA connected to my card.
I also tried some games:http://img301.imageshack.us/img301/1107/pacmanxj0.jpg(HIRES)http://img87.imageshack.us/img87/2020/airheart1vgand9.jpg(DHIRES)
I'm just wondering how to continue. I might finish the PCB layout
tomorrow, so I need to decide whether I make a prototype on my own -
which is a lot of work (566 pads/204 vias) to be done or if I decide
to let some guys make the PCB. But a 268mm x80mm is going to be
expensive in prototype volumes (i.e. 1 or 2). It seems that PCBs are
way cheaper in the US than in Europe...why? I might actually let them
make in the US and ship them here.

Ferdinand



I don't understand. The colours are fine, but the vertical striping is
completely alien to me. Does anyone else actually want it this way?

Using an Apple II+ with RGB as a kid, then a PAL Apple //e, then RGB
Apple IIGS, and finally NTSC //e's and NTSC and RGB //c's here in
Japan, I've never seen that kind of vertical striping.


RGB displays usually produce the "striping"--after all, alternate
pixels are *black* in a hi-res color!  Only low-bandwidth chroma
(like NTSC) blurs it together to look more-or-less solid.

It takes a peek into the future to know that the next pixel will
extend the current color, and the black should be filled in (except
when it shouldn't because it's part of a texture), since any dark
pixel position *could* be past the end of the colored line.

As I've often noted, the way that a good, analog NTSC monitor
renders Apple II graphics is the *standard* for how almost all
graphic designers intended them to look.  RGB cards and displays
were just too expensive to ever be popular in the Apple II age.

That doesn't mean that designers now couldn't target RGB displays,
but then they'll have to choose a "standard" RGB rendering to know
what most people will actually see.

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."