[Coco] To all RGB2VGA builders

[Luis Antoniosi (CoCoDemus)]

In my page I posted my last changes to the board. The new altera code has
been commited to the repo as well.

Basically I add a 3rd blue bit. This makes the colors to look better
calibrated and ease the scanline effect. The are smoother now.

The second change is for the RGBI input. I've added an extra input pin for
the bright component.

But keep in mind to not direct connect digital R,G and B lines into the
RGB2VGA converter. Use a 150R resistor in series for each input, otherwise
the 5V could potentially damage the board. For the new Bright and
CSync/HS/VS they already have their voltage dividers and are safe for a
direct connect.

The RGBI can be switched from the SW2. Notice that the RGB are still read
as analog ports so you have to adjust the voltage trimmer to get the proper
values.

I've tested with Zx-Spectrum +2. In this case, you should use the
speccy.jif or speccy.sof for the Altera as the spectrum clock frequency is
slightly different from the coco3/ntsc.

Also look the last picture I posted my lastest assemblled board. I managed
to use dip switches instead of jumpers, you just have to plie the pins a
little.

I'll design a new version of the board with all the changes.

https://sites.google.com/site/tandycocoloco/rgb2vga


Enjoy,

Luis Felipe.





Luis Felipe Antoniosi