External Memory

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CompMan
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External Memory

Post by CompMan » Tue Aug 26, 2008 3:23 am

How about the idea of external memory? You could use MMC/Sd for mass storage. This would make it easy to put new games on because you could have an interface that allows you to drag new games without reprogramming the ATMEGA644. The other option is to make a reprogrammable game cartridge using EEPROM.

MMC/SD
http://www.captain.at/electronic-atmega-mmc.php

EEPROM
http://www.captain.at/electronic-atmega-eeprom.php

Compman

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uze6666
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Re: External Memory

Post by uze6666 » Tue Aug 26, 2008 3:50 am

I thinkered with the idea of SD memory for game content, but there's not enough RAM to buffer blocks, so it sounded pretty useless. But to use it to make some sort of 200-in-1 game cartidge, that's genius! Good one Compman. I guess we just need to code some sort of custom boot loader. And the SPI port pins were reserved for something like that....

CompMan
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Re: External Memory

Post by CompMan » Wed Aug 27, 2008 7:11 am

I was looking into a bootloader and found a website that has something very similar to what we were looking for. Basically it is an AVR MP3 player. To update the firmware you can put the *.BIN file on the SD card. It will then load and launch the code. I thought this would be a good start.

The site is - http://www.mictronics.de/?page=mp3stick

Compman

psyjax
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Re: External Memory

Post by psyjax » Wed Aug 27, 2008 1:46 pm

Having some sort of portable storage would be excellent. I think folks who are into this sort of thing would love to pass their creations around without the hassle of having to flash it to the hardware from their computer each time they wanna play something. I know at least 5 people who are gonna want one of these baby's :)

Tinctu
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Re: External Memory

Post by Tinctu » Sun Aug 31, 2008 4:02 pm

EXTRA RAM WILL BE NOT CHEAP...
Build in 64KB is enough!!! I mean look at SEGA GENESIS games.
They are awesome and SEGA GENNY has only 64KB...
When You will have SD-CARD... Each level can have 64kb or each screen...
You will load data from SD-CARD so Your game can have 32MB :D or more...

CompMan
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Location: Kent, WA

Re: External Memory

Post by CompMan » Mon Sep 01, 2008 8:12 pm

What if we used external eeprom like the NES did. This way we don't have to work with the FAT file system.

Compman

havok1919
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Re: External Memory

Post by havok1919 » Mon Sep 01, 2008 9:24 pm

CompMan wrote:What if we used external eeprom like the NES did. This way we don't have to work with the FAT file system.
You could, it's just hard to say no to 1Gbyte microSD cards for $4 or whatever they're going for now. ;) By contrast a 128Kx8 serial EEPROM is close to $3 in 100's (and then you have to mount it on a little carrier/socket board, etc.).

The nice thing about SD/MMC/etc. is that reader/writers are simple to find (and dirt cheap) as well as media. FAT is nice for being able to drag and drop data and probably a minimalist read-only filesystem could be done for something like a music player or whatnot. (or if you wanted a datalogger you could add write and just expect that a lot of the onboard flash will be used up) With the '1284 there'd be enough internal RAM to get better performance too.

For the sake of upgrades, we could just use SPI block mode. That really isn't much worse than any other EEPROM/Flash to deal with. We'd have plenty of RAM for holding a sector in a buffer while writing to internal flash. Programming the card is a little harder, but we could use something like CHDMAN from the MAME distribution to do a raw sector dump to the card. (just be careful, don't want to write your AVR program over the top of your hard disk boot sectors.) ;-)

-Clay

Lerc
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Re: External Memory

Post by Lerc » Tue Sep 02, 2008 2:28 am

Wikipedia says "All memory cards must support all three modes, except for microSD where SPI is optional."

Might be a thing to be aware of with microSD. It's not like standard SD is humongous anyway.

There's no requirement to have fat, I've seen other filesystems on SD so if it needs to be ultra simple, a block interface is a possibility.

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