So it's the weekend and I finally got around to giving a good shot at a
simple 480p Dreamcast cable for the Framemeister. This is what I wanted:
- all in one cable, no connecting multiple devices
- either passive or self-powered
- ability to switch to 15KHz mode for compatibility
So I bought a 3"x2"x1" project box from rat shack and combined the schematics for the VGA box with the sync combiner circuit, and wrote up a schematic for a Framemeister cable. I built it, but I put a twist on mine: since you can put the 31/15KHz switch anywhere you want, I decided to put it on the SCART connector. The SCART cable I used to make this cable was fully wired for all pins, so I just disconnected one of the pins that's useless (like pin 12) and instead ran the Dreamcast's VGA Enable pin (If this pin is grounded, you get VGA/480p, if it's floating, you get RGB/240p/480i) up to the SCART connector, where I wired a simple switch to switch whether or not it is grounded.
Pics and schematic included:
Getting started on the first half of the circuit:
Wiring up the SCART side:
Fitting the cables into the holes drilled in the box:
The switch in the SCART connector switches between 480p (from VGA) or 240p/480i (RGB mode):
The box has no switches or ports or anything. Simple and clean.
Hooked up to my Dreamcast. Dreamcast also has a S/PDIF digital audio out.

All of the stuff required to do this can be bought for under $5 total.... except the AV connector. I don't know where one could purchase or salvage an AV connector that has all the pins needed (5v, RGB, H-sync, V-sync) besides from an expensive VGA box. Which is what I did, because my VGA box needed repairs anyway.