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Electronics, coding and hacking. And ADD.

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VGA on ATmega128

2012
28
March

Although I've done VGA signals from micro controllers many times before, I've been pondering lately on introducing a 74LS165 PISO shift register into the circuit. This would increase the resolution from the controller based on the memory available. I'm aiming for 40x25, but I wouldn't be surprised if it were capable of more.

I didn't finish it last night, but I'll show you the progress so far. Here's the breadboard with the shift register attached, and a crystal to it. I also decided to do all, if not most of it, in pure C.

ATmega128 VGA on breadboard

Here's a quick VGA adapter board I made. Who said vero boards are passé?

ATmega128 VGA adapter

Here's the graphics being produced by the ATmega. Not much to show, really, but I was able to verify that the timing was spot-on and the voltage levels were acceptable.

ATmega128 graphics output on the oscilloscope

It's at a very experimental stage right now, I'm only setting the background color, playing with a few on/off's horizontally. The image is perfectly stable, no flickering or shivering.

ATmega128 VGA screen

Here's proof the signal is fine. For some reason I expected 60Hz but ended up with 59... not quite sure why, but we'll see if it's worth digging into. As of now, I don't really care.

ATmega128 VGA screen verification

All right, that's as far as I got last night. Next time I'll have some text on the screen! Oh, and the schematics and sources will obviously be released when I'm done.

Edit: Success. See here.


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  • …A on the ATmega, and fought some timing issues. This is a followup on the test I did earlier ("VGA on ATmega128"), but today, I got a small breakthrough and a proof-of-concept up and running:It's based on a…

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