Wishing to make my own sd card based flash cart.

Discussion in 'GBA - Flashing Hardware and Software' started by azeluk, Nov 27, 2013.

  1. azeluk
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    azeluk Advanced Member

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    Hey every one, I'm currently at college studying in electronics and I have to start my own project, so I decided to try and design my own gba cart that uses an sd card as storage, but I don't know where to start.

    Can any one help me out.

    Many thanks.

    Axel.
     
  2. pwsincd

    pwsincd Garage Flower

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  3. FAST6191

    FAST6191 Techromancer

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    pwsincd linked you to the homebrew carts. They are "just" NOR carts though and I am not sure what they have in the way of saving.
    SD cards, likely even modern ones, are too slow to to read directly from the SD card so things tend to have to be shuffled around. As NOR memory and as RAM of various sorts is often* fast enough they tend to be used instead. Unfortunately you have just now also had to add something to manage transfers around the joint (here most flash cart makers opted for various middle of the road (for 2006) CPLD type devices).
    Similarly we have had a few similar discussions in the past few months, despite it being years on you can not just throw a dart at a digikey ram chip page and have it work either as far as size goes and you have the added perk of a lot of chips moving to very fine pitch or even smaller than normal BGA which is always nice.

    *the GBA slot supercards had RAM onboard, it was still too slow though and you really do not want to be getting into speedpatching GBA games.
     
  4. pasc

    pasc GBATemps official GBA Freak

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    speedpatching ?

    Has anyone done that before ?
     
  5. FAST6191

    FAST6191 Techromancer

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    Most of the GBA slot supercard "fixes" are speedpatches, earlier on when people were using slightly tweaked GBC era carts there were similar things and there may be some stuff made for certain emulators at various points. Equally they are often less "makes the game run at full speed on substandard hardware" and more "makes it so it works or at least does not crash so often".

    Patches to remove framerate caps, have an effective turbo button and similar such things.... I would struggle to even find an example. Anything here would be more tweaking animations and other game level things to speed games up.
     
  6. VashTS

    VashTS Beat it, son

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    do a dreamcast or psx ODE
     
  7. DanTheManMS

    DanTheManMS aka Ricochet Otter

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  8. azeluk
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    azeluk Advanced Member

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    Cheers folks OK so say instead of sd card I used a flash memory kinda like the 512mb x-rom or the 256 ezfa, how do I go about designing like that, is it pic based?.

    Azel
     
  9. FAST6191

    FAST6191 Techromancer

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    By flash memory I assume you mean NOR memory (SD cards are just a type of NAND and too slow, there were NAND to NOR loading cards at one point in time but NOR write speeds are not noted for their speed). 512mb would necessitate some form of bank switching (the GBA can only address 32 megabytes) and either would want some form of paging (unless you want to limit yourself to bank aligned or a single ROM.... which would be pointless for a 512 and less fun for 256). How you would select a ROM I am not sure, most went for some form of loader and a reset upon selection approach, for a first pass I would probably consider something like the N64 third party memory cards and have a pushbutton.

    PIC..... nobody has really designed a top flight new cart in years at this point and even back when it was a price focused iteration on what came before. To that end a pic in 2013 would probably stack against a early 2000's CPLD or even viable FPGA, I do not have numbers here but I would be willing to bet on it. I had hoped someone would emulate save types in hardware rather than patching them (though patching is not hard) to use SRAM and I am not sure a PIC could do that on top of everything else, patching to use a SRAM chip should not be a problem though (short version is search for an ASCII string of SRAM, EEPROM or FLASH and depending upon the also ASCII letters and numbers that follow it you direct identical patches to slightly different locations not far after-- do a binary compare of something patched with EZ4client or GBATA if you want examples).