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AtariAge on Odyssey 2

Posted by LS_Dracon, 12 April 2011 · 886 views

I was reading about Odyssey 2 programming and created a demo, it dysplays AtariAge
on the screen. I think it's not bad for only 2 hours studing the O2 hardware.

I have no plans for this console for now, but I liked some of the 8048 assembly instructions (O2 processor).
It's very similar to Chip8 language that I give a try last year. The hardware also.

Odyssey 2 support 4 sprites on the screen, they are limited to 8x8 pixels. You can draw them as 2x wide. Don't know yet if is possible to re-use like in atari 2600, I hope so.

Also, it support 12 freely moveable objects, but limited to 8x8 pixel images (characters) you find in the BIOS. It's why many of O2 games uses the same sprites. They haven't collision detection, if I understand correctly and can't to overlap each other.
They are used to dysplay text. That's means, 12 letters per row (or screen don't know)

There's no background support, just a grid 8x9 that you can enable / disable each line in the square as desired. It's pretty much limited to draw walls like in Berzerk.

There's 4 quad-sized objects wich I don't know what they are. I think it's gigantic sprites, so with them I can draw a sort of background. I need to test this to know how it works.

All objects are limited to 1 color from a pallete of 8. You have a darker pallete for the background grid only. Don't know if is possible to change the color by line like in the Atari 2600. Hell the A2600 is my unique reference of game programming in assembly :P

Odyssey 2 is surprisely fun to code :)

Here's the rom but there's not only the image you see atached.

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The quad-sized objects are four 8-pixel objects which are placed with 8 pixels between. Crypto-Logic uses four quad objects plus twelve individual objects to display 28 letters total.
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Hm... So it's similar the multiple copies of a sprite in Atari 2600. But I can choose the shapes of them easily.
This is interesting, it's possible to create a good Space Invaders port using them.
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It's a neat platform the Odyssey 2, I haven't been able to find a visual reference for its BIOS characters like a PNG to look at or experiment with in my usual non programmer way lol. Hard to find an Odyssey 2 locally but they come up occasionally where I live. Anyway neat stuff, pretty good color match on the AtariAge. :)
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Here's the Odyssey2 char set : http://www.coprolite.com/art42.html
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