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Game boy emulator project

I will use this README to track my progress on my gameboy emulator project. The objectives of this project are the following :

  • Learn about emulation by attempting to emulate a simple games system.
  • Gain more experience in software design.
    • The code I will be writing will obviously be far from perfect. One idea is to check out existing emulators once I am finished with this project (not before) to try and understand how more experienced developers designed their systems and how I could have gained from their expertise.
  • Gain more experience writing C code.
  • Have fun.
    • It is very easy to feel paralyzed by the inadequacy of the codebase but I have to keep moving forward and complete my tasks. Otherwise, I will never have a working system. It won't be perfect and that's fine, let's have some fun.

More tasks will be added below as I move through the project and gain a better understanding of the system going from the general flow right down to the last detail.

Build and run instructions

If you are running linux you should first download the SDL2 library with the following command :

sudo apt-get install libsdl2-dev

Then run the following command to build and run the emulator (the tetris ROM is currently loaded by default) :

make build-linux && cd src/ && emulator.exe

Milestone 1 : Scrolling the Nintendo logo (running the boot ROM)

This milestone has been reached. We can now scroll the Nintendo logo on to the screen. The tasks below are some suggested improvements for this stage.

Work to be done

  • TASK [test]: verify VRAM data for logo scroll
	8000: 00000000000000000000000000000000
	8010: F000F000FC00FC00FC00FC00F300F300
	8020: 3C003C003C003C003C003C003C003C00
	8030: F000F000F000F00000000000F300F300
	8040: 000000000000000000000000CF00CF00
	8050: 000000000F000F003F003F000F000F00
	8060: 0000000000000000C000C0000F000F00
	8070: 000000000000000000000000F000F000
	8080: 000000000000000000000000F300F300
	8090: 000000000000000000000000C000C000
	80A0: 030003000300030003000300FF00FF00
	80B0: C000C000C000C000C000C000C300C300
	80C0: 000000000000000000000000FC00FC00
	80D0: F300F300F000F000F000F000F000F000
	80E0: 3C003C00FC00FC00FC00FC003C003C00
	80F0: F300F300F300F300F300F300F300F300
	8100: F300F300C300C300C300C300C300C300
	8110: CF00CF00CF00CF00CF00CF00CF00CF00
	8120: 3C003C003F003F003C003C000F000F00
	8130: 3C003C00FC00FC0000000000FC00FC00
	8140: FC00FC00F000F000F000F000F000F000
	8150: F300F300F300F300F300F300F000F000
	8160: C300C300C300C300C300C300FF00FF00
	8170: CF00CF00CF00CF00CF00CF00C300C300
	8180: 0F000F000F000F000F000F00FC00FC00

	8190: 3C004200B900A500B900A50042003C00 -> copyright logo

Milestone 2 : Run through the entire boot process

This milestone has been completed. We now run through the entire boot sequence with the logo check working properly. We can now move on to testing on simple ROMs.

Milestone 3 : Run a simple game with joypad input

  • TASK [cleanup]: move CPU macros into c file and change them into functions

  • TASK [cleanup]: make CPU registers pointers to integers

  • TASK [cleanup]: Improvements can be made to the makefile by looking at standard makefiles

  • TASK [cleanup]: make header files follow the same format (include order, external APIs prefixed but not internal APIs)

  • TASK : Implement enough functionality to display the Tetris intro screen.

    • At this point we shouldn't need joypad input, interrupt handling, etc, but I suspect something is going wrong since I am currently executing as far as reading joypad input but I haven't yet loaded the Tetris intro screen.

  • TASK 2 : Implement enough functionality to read joypad input

    • Implement overwriting hardcoded boot rom with initial cartridge instructions after having executed the hardcoded boot rom.
    • Implement interrupt handling for joypad input.

https://github.com/osnr/tetris/blob/master/tetris.asm

Learning resources

http://bgb.bircd.org/pandocs.htm https://gbdev.gg8.se/wiki/articles/Pan_Docs#Cartridges http://marc.rawer.de/Gameboy/Docs/GBCPUman.pdf https://github.com/gbdev/awesome-gbdev http://www.emulatronia.com/doctec/consolas/gameboy/gameboy.txt

Once I am done I can look at the following emulators (NOT BEFORE) : https://github.com/binji/binjgb