Jeff Epler's blog

XY display update

New CRT, new board, same software...

vgaxy -- create XY scope displays with your VGA card

Software for a virtual terminal and several other toys

Vector patches for xmame 0.94

With this patch applied, xmame 0.94 does vgaxy-style output for display on an oscilloscope in xy mode

More vector game screenshots

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Battle Zone

I really should mention the website of Jed Margolin which has a lot of information about his time at Atari, including his work with vector games.

"Dithered" output increases resolution

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64x48 character terminal

By switching between two values in adjacent pixels, the voltage seen at the scope is an intermediate value between the two.] For instance, to display a pixel at X=128.5, alternate between blue=128 and blue=129. This happens because the pixel clock is faster than the bandwidth of the rest of the system---in particular, this signal is at about 75MHz, while the scope has a "20MHz bandwidth limit" button.

So without complicated extra hardware, I've got a nice 512x512 output, which gives me a 64x48 character vector terminal. It's a lot more readable than this screenshot makes it appear. 768x768 (a 3-pixel ordered dither @ 50MHz) and 1024x1024 (4-pixel, 37MHz) dithered resolutions may also work. Watch this space.

MAME vector display on the oscilloscope

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Asteroids

Yep, it works. Too bad about the low resolution. More game pictures below the fold.

Working Z-axis

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Vector terminal with Z-axis

With a simple transistor, the Z axis works pretty well. The linearity is better now that I'm using some 10b2 tees and terminators (50 ohms) on the X and Y inputs, too.

Vector "text" display

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Simulating a character-cell display

Displaying a message, even.