24x24 LED Game of Life...

What have you built or do you want to design to go with your replica 1

Postby logjam » May Sat 03, 2008 1:49 am

How hard would it be to scale up to 256x256 or 192x99? Would it take a lot more memory or take too much processing power?
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Postby fsafstrom » May Mon 05, 2008 4:23 pm

For 256x256 you would need an 8KB buffer for your bitmap.

The 6522 can shift out 512Kbit per second at 1MHz, you need to send 16KB per 256x256 bitmap, 16x8 Kbit = 128 Kbit.
So if you were able to load the shift register at maximum speed you would be able to send 4 bitmaps per second.

So I don't think you can make any smooth animations but I don't see any problems extending the bitmap to 256x256.

On the other hand, I'm going to let you calculate the cost of the MAX7219 driver chips, they are abut $5 each when you buy them in bulk of 1000... ;-)
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Postby logjam » May Tue 06, 2008 1:21 am

My display will be memory mapped, so as long as the data is in memory it will be displayed. I have some dual port SRAM and a 20MHz shift register for it. I need 60 frames/sec for Space Invaders (long story).

There are current controlled drivers for multiplexed LED systems that run $.50 a piece. Still a lot though! :)

I'm thinking about making a kit for people that is more reasonable. 96x72 or 64x48.

I'm leaning towards 96x72 because it would be 12x8 inches. I've converted a few pictures to Red+Green at 96x72 with 4 bit gray scale and they look great. I've got to finish selling Altair kits so I can start working on my LED projects! :)
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Postby vbriel » May Tue 06, 2008 7:53 am

Space Invaders? I thought you were doing a scrolling marquee sign? LOL, I want a stadium scoreboard! Ahhh, what to do with too much time, Alaska winter, and a billion LED's :D

Vince
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Postby fsafstrom » May Tue 06, 2008 11:42 am

The MAX7219 is both expensive and not suited to drive large displays.

There are microcontrollers that costs a lot less and can do a lot more...
Maybe a microcontroller that halts the CPU, access the momory (DMA), let the CPU continue and then generates the display would be a much better solution.

Alaskan winter and billions of LED's...
Are you thinking virtual Aurora Borealis ? 8)
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Postby logjam » May Wed 07, 2008 7:44 pm

The original Space Invaders ran on an 8080. It had a 256x244 bitmap display turned on its side.

What better to do with an Altair than make it an arcade machine?

I'm tempted to make it 320x248 instead of 256x248, but we'll see.

The display will probably have to be addressed as 8192 pixels wide and 8 pixels high.

If I were to do this project, I would make 4 panels with their own addressing. That way the data rate can be slower. There would be a micro controller and dual port SRAM (no halting required).

This is the driver I would use:
http://www.allegromicro.com/en/Products ... /index.asp

It incorporates a shift register, latch, and constant current drivers all in one package. The price is very good at 500 (.63).

My smaller display of 96x72 or 64x48 would use these too. I imagine I can get the whole kit for a 96x72 display down to $250-300. That display would be able to display 256 shades of red and green. Preliminary photoshop tests show most pictures look pretty good without blue. :)
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