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So, here's the teletext generator I've just finished.
This is an ATMEGA. It produces the teletext.
This is the sync separator which extracts the sync signals from the video input.
so that I can hook up the teletext signal onto the video input.
The teletext signal goes from here to an inverter
which isn't unnecessary yet.
Video goes in and out here.
Here we have a video source: A Commodore DTV
with games and
a Commodore Basic mode.
Now let's switch to teletext...
And there is teletext.
I've attached a logic analyzer board, so we can see what happens in the circuit.
Here's the vertical sync signal.
And these are color bursts, as they are extracted from the sync separator.
They are used as horizontal sync.
Here we see what the teletext generator does.
That's the teletext.
Zooming out.
Here's the teletext and after that, the visible lines would go.
Quite easy actually.