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")

• No extra features currently implemented, just compatible with retro-go
• External flash savings to come in the future.
• See the zelda document for more information.

Usage

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 game and watch backup repo. 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.

Install python dependencies (>=python3.6 required) via:

pip3 install -r requirements.txt

Download STM32 Driver files:

make download_sdk

The default programmer interface is stlink, you can chose a different interface via the ADAPTER variable. For example, ADAPTER=rpi.

NOTE: if you are flashing a 64MB chip, add LARGE_FLASH=1 to your make command!

I recommend pressing the power button at the same time you press enter. Note that the same configuration parameters have to be passed to each make command.

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_patched

# 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
# Note: only set the LARGE_FLASH=1 if you have a >=64MB chip!
make PATCH_PARAMS="--device=zelda" LARGE_FLASH=1 flash_patched

# in the retro-go repo
make clean
# In this example, I'm assuming you have a 64MB flash chip (60 = 64 - 4)
make -j8 EXTFLASH_SIZE_MB=60 EXTFLASH_OFFSET=4194304 INTFLASH_BANK=2 flash

Build and flash using Docker

If you are familiar with Docker and prefer a solution where you don't have to manually install toolchains and so on, expand this section and read on.

To reduce the number of potential pitfalls in installation of various software, a Dockerfile is provided containing everything needed to compile and flash Custom Firmware (CFW) to your Nintendo® Game & Watch™ system. This Dockerfile is written tageting an x86-64 machine running Linux.

Steps to build and flash from a docker container (running on Linux, e.g. Archlinux or Ubuntu):

# Copy the content of a docker directory from this repo. To create the image, cd to the folder where you put the files and type:
sudo docker build -t game-and-watch-patch:latest .

# When done, use the image to create a container with the attached docker-compose.yaml file.
# You have to edit the compose file and set the path to the directory with your firmware backup (volumes section of the file).
sudo docker compose up -d

# This will create and run a container game-and-watch-patch.
# The firmware backup files will be mounted into /tmp/firmware of the container.
# Now, go inside the container copy the backup files and proceed as described above in the Usage section.
sudo docker exec -it game-and-watch-patch /bin/bash

Troubleshooting/FAQ:

Error: FSIZE in DCR(1) doesn't match actual capacity. while flashing.

If you receive this error, you can safely ignore it. It doesn't impact flashing or the final device at all.

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.

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)!