Custom firmware for the newer Nintendo Game and Watch consoles.

What is this?

This repo contains custom code as well as a patching utility to add additional functionality to the stock Game and Watch firmware. In short, this project allows you to run the firmware your game and watch came with along side retro-go.

Features

• Works correctly with retro-go in internal flash bank 2.
• Press button combination (LEFT + GAME) to launch retro-go from internal flash bank 2.
• Run make help to see all configuration options.

Mario (PATCH_PARAMS="--device=mario")

• Ability to store the entire firmware in internal flash! No external flash required!
  • Option to remove the "Mario Song" easter egg.
  • Option to remove the 5 sleeping illustrations.
  • LZMA compressed data.
  • Intelligently move as much data to internal firmware as possible.
• Configurable timeouts.
• Ability to play SMB1 ROM hacks via --smb1=path-to-patched-smb1-rom.nes
• Ability to dynamically load SMB1 ROM hack sprites for the clock via --smb1-graphics=path-to-patch.ips
  • Can add up to 8 additional graphics sets.
  • Cycle through via the down button on the clock screen.
  • Add all your ips files to ips/ and have the patcher automatically discover them via the flag --smb1-graphics-glob
• Dumps SMB1 and SMB2 ROMs that are playable by other emulators.
• See the mario document for more information.

Zelda (PATCH_PARAMS="--device=zelda")

• Ability to remove the second beep in TIME/CLOCK via --no-beep
• External flash savings to come in the future.
• See the zelda document for more information.

Usage

This repo uses the gnwmanager cli tool. See it's instructions on how to install.

Install game-and-watch-patch python dependencies (>=python3.6 required) via:

pip3 install -r requirements.txt

Place your internal_flash_backup_${DEVICE}.bin and flash_backup_${DEVICE}.bin in the root of this repo. To extract these from your gnw system, see the gnwmanager unlock tutorial. For example, if we are patching the mario game and watch, we need the files internal_flash_backup_mario.bin and flash_backup_mario.bin in the root directory of this project.

See the appropriate section below for your device model.

For additional configuration options, run make help.

Retro Go (Mario)

Since most people are going to be using this with retro-go, want the minimum amount of external storage used, and don't care about the sleeping images or the mario song easter egg, here are the recommend commands. Note that this uses an undocumented 128KB of internal Bank 1 and requires a patched version of openocd installed.

```

in this repo

make clean make PATCH_PARAMS="--device=mario --internal-only" flash

in the retro-go repo

make clean make -j8 INTFLASH_BANK=2 flash ```

Retro Go (Zelda)

This assumes you have upgraded the external flash to something larger than 4MB. See the zelda document for using retro-go with the stock 4MB flash chip.

```

in this repo

make clean make PATCH_PARAMS="--device=zelda" flash

in the retro-go repo

make clean

In this example, I'm assuming you have a 64MB flash chip (60 = 64 - 4)

make -j8 EXTFLASHSIZEMB=60 EXTFLASHOFFSET=4194304 INTFLASHBANK=2 flash ```

Build and flash using Docker

Troubleshooting/FAQ:

Unable to install python dependency keystone-engine on rpi3

If you are unable to install keystone-engine on a raspberry pi 3, try: 1. Update the GPU RAM to 16MB from raspi-config 2. Build and install keystone-engine from source (should take ~15 minutes): git clone https://github.com/keystone-engine/keystone cd keystone/bindings/python/ python3 -m pip install .

Development

Main stages to developing a feature: 1. Find a place to take control in the stock rom (usually function calls). 2. Add the stock function and its address to Core/Inc/stock_firmware.h. 3. Implement your own function, possibly in Core/Src/main.c. There's a good chance your custom function will call the function in (2). You will also probably have to add -Wl,--undefined=my_custom_function to LDFLAGS in the Makefile so that it doesn't get optimized out as unreachable code. 4. Add a patch definition to patches/patches.py.

Protocols

We store information about how much external flash this firmware uses at internal-flash offset 0x01B8. This location is in the HDMI-CEC handler in the vector-table; this is unused for all game-and-watch purposes, so serves as a safe, standardized spot to put a bit of data. At this location we store the following data:

C struct { external_flash_size: 24; // This value * 4096 is the amount of external flash used by this firmware. must_be_4: 4; // "magic" value that would never be valid in any real hdmi-cec firmware. 0x4 is in the hardware perhipheral space. is_mario: 1; // This is the mario firmware. is_zelda: 1; // This is the zelda firmware. _unused: 2; // Reserved for future use. All 0 for now. }

Journal

This is my first time ever developing patches for a closed source binary. I documented my journey in hopes that it helps other people. If you have any recommendations, tips, tricks, or anything like that, please leave a github issue and I'll update the documentation!

Acknowledgement

Thanks to the community that made this possible! This repo was built with the help of others. Repos referenced during the development of this project:

• game-and-watch-retro-go by kbeckmann
• game-and-watch-backup by ghidraninja
• game-and-watch-base by ghidraninja
• game-and-watch-decrypt by GMMan
• game-and-watch-drawing-song-re by jaames

I would also like to thank the stacksmashing discord for all the help (special shoutout to @cyanic)!