blazer82 / gb.teensy

Gameboy emulator for the Teensy 4.1 microcontroller

Teensy Gameboy

This is a work-in-progress Gameboy emulator for the Teensy platform. It requires some custom hardware and wiring in order to work properly.

Features

• Runs Tetris
• Passes Blargg's CPU instruction tests
• Audio output (4 separate channels)

Dependencies

The project uses a Teensy 4.1 as its main processing unit and storage device (SD card).

The FT81x Arduino Driver is used as a display system.

Additional wiring is required for audio output and button input.

Wiring

Display

For display wiring please refer to this guide for the FT81x Arduino Driver.

Buttons

Button wiring is straight forward and doesn't require any pull-up resistors:

Audio

For proper audio output some filter and amplifier circuitry is required:

Tip: Audio output is most authentic with a Gameboy replacement speaker.

Running and Loading a Game

Game ROMs are not included with this repository and have to be provided via SD card! Make sure the SD card is formatted using the FAT32 filesystem using Master Boot Record partitioning style. File names should follow the 8.3 MS-DOS style.

As of now, the ROM to be loaded has to be specified inside src/main.cpp, e.g:

Cartridge::begin("tetris.gb");

Contributing

Any contribution is welcome! Please have a look at open issues and pull requests or create your own.

Credits

Substantial contributions have been made by:

• @granthaack

The code builds upon the following libraries:

• Arduino
• Teensyduino
• TeensyTimerTool

gb.teensy's Issues

Power consumption?

Hi,
really interesting project. May I ask how much power the breadboard version consumes?
With the original gameboy I was able to play around a day. How long would it be with this setup?

Create SD Card Menu

Create an SD card menu to browse ROM files. Preferably with some kind of memory to remember the last loaded ROM, so the menu doesn’t have to be the first thing the user sees.

Implement VRAM Background Tile Addressing Modes in the PPU

VRAM tile data can be accessed in two different ways (0x8000 method and 0x8800 method). Currently the emulator assumes the 0x8000 method and does not check for the other one.

More info here:
https://gbdev.io/pandocs/#vram-tile-data

Document Wiring

For better reproducibility document the wiring especially for buttons and sound output.

Implement Background Tile Map Switching

There are two different tile maps that can store tile data. Currently, the emulator is assuming that all tile data is coming from the first tile map (MEM_VRAM_MAP1). It does not check to see if the game is requesting the second tile map (MEM_VRAM_MAP2)

Fix Sound-Related Lags

Sporadically, the execution of the ROM hangs for a brief amount of time. The issue has appeared with changes to the APU and is most likely related with the hardware timers.

Implement Wave Sound Channel

The wave sound channel is currently missing.

For more information about this channel see:

https://gbdev.gg8.se/wiki/articles/Gameboy_sound_hardware#Wave_Channel
https://gbdev.io/pandocs/#sound-controller

ROM Names Must Be <= 8 Characters on the SD Card

Probably a limitation of the FAT32 library that we're using

Game and music running, but no display

Hi, so I tried the project with your ft81x-driver pcb, the same display and your code and made a custom pcb for wiring and the audio. My problem is, that the game is running with sound (I can also hear feedback when I press the buttons), but I can't see anything on the display. Communication with the FT812-Chip seems fine, it is responsive. The all pixels on command directly to the display-controller is also working. I've also reassembled the ft81x-pcb multiple times.
It seems to be a problem in the connection between the ft812 and the display controller.
Has anyone had this problem?

Implement Window Rendering in the PPU

Currently the PPU will render sprites and background. It should be upgraded to render windows as well

Fix Noise Issue During Quiet Parts of Tetris

When entering a quiet part of the Tetris Game (e.g. after no activity on the start screen) all sounds stop as expected with each channel becoming noisy again after a short amount of time.

Synchronize CI Build Dependencies with Project Dependencies

Maybe just use the project's existing platform.ini instead of creating a new one.

Implement Negate for Frequency Sweep

For more information see https://gbdev.gg8.se/wiki/articles/Gameboy_sound_hardware#Frequency_Sweep

Add Support for Cartridges

Add support for more cartridge types, possibly with ROM loading from external storage.

--> Merge (and maybe adapt) #1

Control emulation speed

Hi @blazer82 ,

first of all thanks for the great work!
I've rebuilt it a bit and use it with a 4 "TFT touchscreen. Depending on how I configure it, I have speeds of around 30% above and below 100%. Therefore, I suspect that somewhere there is a constant factor for reducing the speed is. Can you tell me where?

Thanks very much!

LCD Status mode prevents Dr Mario and other games to start to start

I'm adapting your code for the PyPortal - I found out that some games are expected the mode 0 instead of mode 1 when LCD is deactivated, and endup in infinite loop. I started successfully some other games by changing the mode to 0.

https://github.com/blazer82/gb.teensy/blame/396e85728ed82401edac8a3bac3faf501a616234/lib/PPU/PPU.cpp#L251