View Full Version : composite to VGA

January 27th, 2019, 03:49 AM
While having a tussle with the vertical hold on my Phillips CM8833 I wondered if I could drive a VGA monitor from a PC with the composite signal from the birdsnests that I keep assembling. It turns out there are muliple little converter boxes that do the trick on Ebay etc. Has anyone got any views (pun!) on those?
I would be looking to output from my circuit a regular HSYNC (50Hz), VSYNC (15.625Khz) (often from a 6845 IC) and a video signal, all at 5volt logic levels. Of course, I currently have a range of favourite little circuits (a couple of gates, resistors and diodes) to combine those signals to a sort of ragged PAL signal, and currently I squirt that into the CM8833.
In truth, I see that converter box as a dirty fix - I like to know what is going on in a circuit. It would be even better if I could avoid having to mix those signals before conversion, so has anyone come across a homebrew circuit to accept TTL syncs & signal, and to output a VGA signal?

Paul, Portsmouth, UK

January 27th, 2019, 09:36 AM
I have a fourdja that does it well.

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