Lukas Werner's VGA project makes room for the pixels you never see

Lukas Werner’s VGA tutorial describes counting beyond a 640-by-480 picture to account for the time outside the visible image. His project uses a DE10-Lite FPGA, and he estimates spending more than 10 hours getting the timing right. Even making a screen display a solid color involved that much debugging.

I like having that work made visible. Werner describes horizontal and vertical counters that track progress through a frame, including the intervals outside the picture. You have to account for the time between visible lines as well as the lines themselves. That gives a curious reader something concrete to follow before worrying about how an image gets stored.

The clock numbers deserve care. Werner describes deriving 25 MHz from the board’s 50 MHz clock, while identifying 25.175 MHz as the standard timing. His 25 MHz project clock is an approximation. I’d keep both numbers in the explanation; rounding away the distinction would hide one of the choices he discusses.

Werner says the red-light buttons in his illustrations are interactive. If you’re curious about how a display receives its picture, I’d start with those diagrams and follow a counter through a line, including the off-screen interval. I wouldn’t buy a board before finding out whether that part interests me. The write-up gives you a way to approach the timing before taking on the hardware.

Werner eventually describes displaying Asterix and experimenting with transparency. I’d stay with the solid-color stage until I could explain when the color signal should appear.