How about useing the new ATMegaX series

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MrZANE
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Joined: Tue Sep 02, 2008 11:47 am

How about useing the new ATMegaX series

Post by MrZANE »

Hi everyone.

This is my first post here.... Soo be nice ;-)

I've just spend a little while reading the different topics in this forum and I'd like to add a couple of thoughts of my own.
I must admit that I don't know if the CPU&|hardware is already set in stone, if thats the case just ignore my little topic.

Since this whole design is speed reliant and the more speed the more possible features (incl. PAL support),
how about using the ATxmega128A4?
This CPU runs at 32 MHz, has DMA for copying data to/from peripherals/data and a very nice DAC that might be used to generate the sound in stereo.
It also has twice the ram (And the possibility to add up to 128MB of memory but that would require a lot of pins).
Porting the code shouldn't be to hard.I realize that it isn't available in DIP package but TQFP 44 isn't that difficult to solder and
when the hardware is all done and running it really shouldn't break (unless of course if some of the critical fuses gets changed).
There are also TQFP to DIP adapter boards that could be used, but I haven't checked if they are pin to pin compatible with the old Megas so It might or might not be a drop in replacement.

Well these are just thought from a guy that haven't even built the hardware.
But from what I see in the pictures and the forum it seems like a very nice DIY gaming console.
Well, have to go back to work, writing a Quickshifter for motorcycles (It uses an Atmega88).

/Jimmy
havok1919
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Re: How about useing the new ATMegaX series

Post by havok1919 »

MrZANE wrote:Hi everyone.
Since this whole design is speed reliant and the more speed the more possible features (incl. PAL support),
how about using the ATxmega128A4?
The way I see it, at some point things stop being "sporting". ;-)

An ATxmega128 in QFN is going to be <$5/ea in 100's. For <$7/ea in 100's we could just get a AT91SAM7S128... That's an ARM7 @ 55MHz, 128K Flash, 32K of RAM (plus USB, A/D, etc). Or, for <$9 you can get a STM32F101RET6 which is a Cortex-M3 (ARM) core @ 36MHz with 512K of Flash and 48K of SRAM (with 12 bit D/A, A/D, etc.).

After a while, the whole 'minimalist' thing starts to break down and you just have so many computing resources and so much RAM that it becomes less 'fun'. ;-)

I kinda like the Xgamestation simply because you do still need to sit pretty low on the hardare to get good performance from it. The Hydra is interesting if only because the Propeller is kinda funky... OTOH, those each have drawbacks. Some people won't want to put the time/effort in on a architecture from the 1970's (8051 assembly language-- I dunno how useful their BASIC is) for the xgamestation, and the Propeller is a non-trivial learning curve (it strikes me as a bit of a hammer in search of nails; maybe just a hobbiest curiosity more than anything else).

I think the UZEBOX is a good middleground-- you can use 'C', the AVR is relatively modern and useful, and what you learn with it will be useful on other projects.

All that having been said, the xmega's are kinda neat and they'd easily enough drop in to the existing architecture. At some point they may be a necessity if only to get stable operation at the 8x NTSC colorburst CPU speed. The PDI is kinda neat, the DMA's could be good, and they should be lower power with the 3.3V rails. Unfortunately they're not pin compatible, but it still wouldn't be *too* expensive to try protyping them at some point.

-Clay
Lerc
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Re: How about useing the new ATMegaX series

Post by Lerc »

I see where you're coming from but I'd have to disagree when it comes to the xmega. I think it's just a better fit for the designed task. Remember the chip currently in use is fairly heftily overclocked.

With regards to arm and so forth, I'd be quite keen on those as well. Not that I'd want to replace a Uzebox with an Armbox, I'd just want one of each :-)

For the point of view from having something to play games and stuff on, Challenging is good but Just as challenging and getting more results is better.

For pure fun, you could make all sorts of things. Two xmegas an arm and a partridge in a pear tree all talking on I²C would be crazy fun.
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uze6666
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Re: How about useing the new ATMegaX series

Post by uze6666 »

Challenging is good but Just as challenging and getting more results is better.
There's this thing called a PC, some have awesome 3D cards and the results are much better than a Uzebox! ;)

Seriously, I initially saw the xgamestation but it was way too underpowered and the 2600 look it produced didn't appealed to me. Then there was the Hydra which was too powerful and had this weird and complicated propeller chip. Havok's really reading my mind here, because thats exactly why I built my project using an Atmel. Something in between, cheap, easy to understand and code for.

Now IF the XMega would have been available at that time, I would have use it. First because I would have had a bit more speed without the need to overclock. Second because it had more internal RAM and the event system and DMA would have helped my get closer to a more decent resolution of 256x240. It would have been as much challenging to write the kernel thought. And learning the new features would have left room to grow a bit.

That said, I have already been thinking about a "Uzebox 2". The neat thing is that it would be backward compatible in software and hardware (well, pins would change) , since its the same architecture and instruction set.

Since I have plenty of things to do with the Uzebox, I'll get back to its successor when the chips are available.

Cheers,

Uze
Lerc
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Re: How about useing the new ATMegaX series

Post by Lerc »

I agree that there is a certain advantage to making things with chips that actually exist.

I intend to use my powerful skills of procrastination to ensure that when I get to making things, the chips will be available.
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kscharf
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Re: How about useing the new ATMegaX series

Post by kscharf »

Well at least with the mega1284 and the xmega parts there IS room to grow.
Neither of these are far removed from the mega644 in complexity or price
all three parts are really in the same ballpark. An ARM is in another league,
although some ARM7 parts are not much larger in ram/rom/io than the '644.
Nice thing about AVR and XMEGA is that the development tools are free to cheap
in price.
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