AVR Based Real-Time Video Signal with Audio

The project, known as Craft, was developed in order to generate sound and VGA video signal on a single AVR chip.

The Craft is considered as a demo that runs on its own minimalistic demo platform based on ATmega88 microcontroller. This microcontroller generates 45 full VGA display lines at almost 60Hz frame set since it is clocked at 20MHz. During the VGA horizontal blanking periods, sound is generated which provides an enough for good chip-sound quality with a sampling rate of 3149kHz. There are 4 sound channels that can be played by the sound player and for best performance, all the operation is programmed in pure assembly language.

Three analog voltage lines consisting of red, green, and blue are contained in a video signal. During the visible parts of the video frame, they vary between ground and 0.7V. For the software to be able to change the current color in a single clock cycle using the instruction, a 2-bit digital-to-analog conversion for each of these signals is performed. For the sound, the volume of each channel can be individually controlled. This excludes the triangle channel, which always plays at full volume.
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