Making a JP Pokemon Crystal RTC Flash Cart
Channel: makho
Date: 2019-04-13

I took a perfectly working JP Pokemon Crystal cart and converted it to a RTC flash cart. I can flash a US version of Crystal, the original JP version of Crystal, any Crystal based ROM-hacks such as Crystal Clear or Prism, or nearly anything else. Anything that supports an in-game clock (like Crystal) will have a working in-game clock when ran on this hardware. 

This flash cart is reflashable with several different cart readers:

Sanni Cart Reader: https://github.com/sanni/cartreader
or my cart reader based on Sanni's which I'll be posting soon

GBxCart RW: https://shop.insidegadgets.com/product/gbxcart-rw/

BennVenn's Joey-Joebags (requires firmware ver 3.36): https://bennvenn.myshopify.com/products/reader-writer-gen2

JRodrigo's Cart Flasher (tindie, not etsy): https://www.tindie.com/products/JRodrigo/cart-flasher-for-gameboy/

Or any of MrHDR's cart flashers: https://github.com/MrHDR/GBFlasher-Micro


Now this will require an AM29F016 chip (check ebay or aliexpress) and an adapter PCB. You can get the files from JRodrigo's github: https://github.com/JRodrigoTech/FLASH-ROM-Adapter-for-GameBoy

and then order the adapters from any custom PCB manufacturer. OSHPark is probably going to be the cheapest for low volume orders (min qty: 3, orderable in multiples of 3) but do note that if you order from OSHPark, the boards will have little rough spots that need to be cleaned up with a file due to the panelization process: https://i.imgur.com/dLS2jFY.jpg

In particular, you want the TSOP-44L adapters for Pokemon Crystal carts. For other carts, e.g. JP versions of Pokemon Gold and Silver, you can use the SOP-32L adapters which are a bit easier to solder. You should open your donor cartridge before ordering anything to ensure that you are getting the proper adapter. 

I ordered the 1.6 mm boards but I meant to order 0.8 mm boards. The 1.6 mm boards worked and even fit fine but 0.8 mm boards might be the better option. 

JRodrigo also sells fully assembled carts: https://www.tindie.com/products/JRodrigo/pre-modded-flash-cartridge-with-mbc3-rtc-timer/

or just preassembled (SOP-32L) adapters: https://www.tindie.com/products/JRodrigo/flash-memory-adapter-for-some-game-boy-cartridges/

You can also use the AM29F032 chip for 4 MB ROM support but those chips are an order of magnitude more expensive to source. 

If you are interested in making your own FRAM version of these carts (does not need a battery to save but still needs the battery for RTC), check out MrHDR's version based: https://github.com/MrHDR/MBC3-Flashcart

The original is from retroreboot.net but it has been slightly modified to use cheaper SMT parts. Otherwise they are the same cart. These carts are functionally identical. 

If RTC (real-time clock) support is not important to you, InsideGadgets makes some really nice hardware clones so you do not have sacrifice any OEM carts: https://shop.insidegadgets.com/