ATmega8 Video Overlay

A few years ago I set about trying to design a very cheap and simple way to superimpose flight data on live video being transmitted over amateur television. Specifically, the data would include things like Latitude, Longitute, and Altitude, among other text including an identifier like my callsign.

Before I go on, I want to point out two other designs I really like. The first I found when researching how others had tried to tackle this goal. William Cooke submitted his AVR COG as an entry into the 2004 AVR design contest. What's neat about it is that it does not require a separate video sync chip. The second design came about after a student studying at MIT contacted me. Ben Gelb, KF4KJQ, wrote me a few years about about my circuit, and I mentioned to him how elegant William's was. With that, he then set about doing an superb job of combining all the strengths of the designs together. Therefore, I highly recommend you take a look at his page and see what he's done.

Tuesday, Jun 26, 2007: I'll add more on my design in the next couple days. Seeing that this page has just gotten a lot of attention from being posted on the Makezine Blog has caused me to get my butt in gear and add some content!

For now, here's the result of the circuit showing some test video:

The breadboard (laying on aluminum foil because of the finicky LM1881):

The schematic:

Sorry, the source is poorly commented right now...
But here it is anyway.