I created this repo to help document my personal experiance in creating a GB flash card hearby called ArduFlashGB (name not will most likey change.)
More will be updated soon.

These are good links for information regarding this project.
Digital-Circuitry:
http://www.digital-circuitry.com/GameBoy.htm

InsideGadgets Blog:
https://www.insidegadgets.com/2011/03/19/gbcartread-arduino-based-gameboy-cart-reader-%E2%80%93-part-1-read-the-rom/
https://www.insidegadgets.com/2011/03/28/gbcartread-arduino-based-gameboy-cart-reader-%E2%80%93-part-2-read-the-ram/
https://www.insidegadgets.com/2011/04/07/gbcartread-arduino-based-gameboy-cart-reader-%E2%80%93-part-3-write-to-ram/

Jazz Disassemblies Blog:
http://jazz-disassemblies.blogspot.com/2013/10/gameboy-mbc-which-to-choose.html

Everything you always wanted to know about GAMEBOY: (in pdf format in documents folder)
http://www.devrs.com/gb/files/gbspec.txt

Post by xzakox on Chipmusic.org forums:
http://chipmusic.org/forums/topic/2988/mbc5-clone-in-cpld/

reinerziegler's blog:
http://reinerziegler.de/readplus.htm#GB_Flasher

Marc Rawer's Blog:
http://marc.rawer.de/Gameboy/

Dillon Nichol's Blog: (he has his carts for sale on Tindi)
http://tinkeringetc.blogspot.com/p/homebrew-gameboy-cartridge.html

MBC-5 CPLD blog:
http://home1.stofanet.dk/hvaba/gameboy/mbc5cpld/

qwertymodo's Posts about his CPLD based cart on Nesdev forums:
http://forums.nesdev.com/viewtopic.php?f=20&t=9443&sid=6d7f7b9e4511b7dcb22689f2313be0eb

Another post by xzackx on chipmusic forums
http://chipmusic.org/forums/topic/2988/mbc5-clone-in-cpld/

Wiki artical about the MBC-5 memory controller:
http://gbdev.gg8.se/wiki/articles/MBC5

gitourious.org c code implimentation of a MBC-5 Memory controller:
https://gitorious.org/bgameboy/bgameboy/source/a7ffbd784b9f59d248df8e680ae4e8cc5543308b:gameboy/cartridge/mbc5/mbc5.cpp

pastebin.com VHDL code implimentation of an MBC-5 (Unfinished?)
http://pastebin.com/c1SyhLEn

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of Nintendo Co., Ltd. of Kyoto, Japan.