happy-ferret / hnes

NES Emulator written in Haskell

hnes

Welcome to hnes. hnes is a NES emulator written in Haskell.

Screenshots

Mapper support

The following mappers are supported:

• NROM (0)
• UNROM (2)
• AOROM (7)

Lots of games run, but more don't. You can see which roms are compatible here: http://tuxnes.sourceforge.net/nesmapper.txt The best games seem to be MMC3, so that is a priority.

Mappers are basically custom memory modules that exist on the cartridges themselves, that allow referencing more memory than the NES originally shipped with. Sometimes they even do computation. A very clever idea, but a nightmare to emulate, since each mapper has to be emulated as well

Controls

Nintendo	Emulator
Up, Down, Left, Right	Arrow Keys
Start	Enter
Select	Space
A	Z
B	X

Building

Get Stack for building Haskell projects.

Windows instructions:

$ stack exec -- pacman -Sy mingw-w64-x86_64-pkg-config mingw-w64-x86_64-SDL2
$ stack build

OS X instructions:

$ brew install sdl2
$ stack build

Ubuntu Linux instructions:

$ sudo apt-get install libsdl2-dev
$ stack build

FreeBSD instructions:

$ pkg install sdl2
$ stack build

Running

To run:

stack exec -- hnes roms/tests/cpu/nestest/nestest.nes

Task list

• Basic structure
• Mappers
  • Loading roms
  • Mappers
    • UNROM
    • NROM
    • AOROM
    • CNROM
    • MMC1
    • MMC3
• CPU
  • All official opcodes
  • All illegal opcodes
  • Nestest passing
  • Blarggs CPU test roms passing
• PPU
  • SDL integration
  • Background rendering
  • Scrolling
  • Sprite rendering
  • VBlank timing for Battletoads edge case
• APU
• Controller input handled
• Performance tuning
• Command line interface
  • Parse args
  • Use optparse-applicative
  • Some debug params?

Tests

There's a small test suite that is used to check for CPU and PPU accuracy. They use test roms rather than hand coding tests.

Just run stack test:

Known issues.

There are so many, where do I even begin.

• Performance is pretty average still. I get around 80 fps on my 2015 i5 MacBook.
• VBlank timing is off. I don't know the exact reasons, but it causes scrolling issues.
• Some issues around mirroring that should be investigated. When you are high up in the map in Super Mario for instance, the screen flickers weirdly: