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https://github.com/Kevoot/LaiNESwitch
Cycle accurate NES emulator based on LaiNES
https://github.com/Kevoot/LaiNESwitch
Last synced: about 2 months ago
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Cycle accurate NES emulator based on LaiNES
- Host: GitHub
- URL: https://github.com/Kevoot/LaiNESwitch
- Owner: Kevoot
- License: bsd-2-clause
- Created: 2018-05-23T03:04:43.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2018-07-29T18:33:48.000Z (about 6 years ago)
- Last Synced: 2024-07-18T03:43:52.974Z (2 months ago)
- Language: C++
- Size: 695 KB
- Stars: 76
- Watchers: 11
- Forks: 5
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
LaiNES - Nintendo Switch Port
======
Original by [AndreaOrru](https://github.com/AndreaOrru/LaiNES)
Port by [Kevoot](https://github.com/Kevoot)
Compact, cycle-accurate NES emulator in ~1000 lines of C++.
## How are lines counted?
There have been some discussions about how the number of lines has been calculated. The claim of ~1k lines doesn't include the libraries (boost and nes_apu). Future plans include eliminating those dependencies to make the code base even slimmer.
```
[andrea@manhattan src]$ cloc .
24 text files.
24 unique files.
1 file ignored.
github.com/AlDanial/cloc v 1.70 T=0.03 s (780.3 files/s, 63170.2 lines/s)
-------------------------------------------------------------------------------
Language files blank comment code
-------------------------------------------------------------------------------
C++ 11 210 110 1163
C/C++ Header 12 87 7 285
-------------------------------------------------------------------------------
SUM: 23 297 117 1448
-------------------------------------------------------------------------------
```
## Requirements
To Run:
- A method of launching homebrew (NRO files)
To Build:
- libnx + devkitpro [See](https://github.com/switchbrew/libnx);
- From the pacman packages for libnx:
-- sdl2, sdl2_image, sdl_gfx, sdl_mixer, jpg and png libs as well
## Building and running
- cd to the root directory and type `make`
- Put the resulting LaiNes.nro file on the Switch's SD card under /switch/LaiNes
- ROMs go in /switch/LaiNes/game
## Usage
The emulator comes bundled with a simple GUI to navigate the filesystem and set preferences. Use DPAD and 'A' to operate it. 'R' toggles between emulation and menu.
## Compatibility
LaiNES implements the most common mappers, which should be enough for a good percentage of the games:
- NROM (Mapper 000)
- MMC1 / SxROM (Mapper 001)
- UxROM (Mapper 002)
- CNROM (Mapper 003)
- MMC3, MMC6 / TxROM (Mapper 004)
- AOROM (Mapper 007) <-- EXPERIMENTAL
You can check the compatibility for each ROM in the following list:
http://tuxnes.sourceforge.net/nesmapper.txt
## Technical notes
The 6502 CPU and the PPU are implemented in just 219 and 283 lines of code respectively.
Some clever meta-programming tricks are used to keep the codebase compact.
Here is a good example of how this is achieved:
```c++
/* Cycle emulation.
* For each CPU cycle, we call the PPU thrice, because it runs at 3 times the frequency. */
#define T tick()
inline void tick() { PPU::step(); PPU::step(); PPU::step(); ... }
...
/* Addressing modes.
* These are all the possible ways instructions can access memory. */
typedef u16 (*Mode)(void);
inline u16 imm() { return PC++; }
...
inline u16 zpx() { T; return (zp() + X) % 0x100; }
...
/* Fetch parameter.
* Get the address of the opcode parameter in a, and the value in p. */
#define G u16 a = m(); u8 p = rd(a)
...
/* Instruction emulation (LDx where x is in registers {A, X, Y}).
* upd_nz, not shown, just updates the CPU flags register. */
template void ld() { G; upd_nz(r = p); }
...
/* Execute a CPU instruction.
* Opcodes are instantiated with the right template parameters
* (i.e. register and/or addressing mode).*/
void exec()
{
switch (rd(PC++)) // Fetch the opcode.
{
// Select the right function to emulate the instruction:
...
case 0xA0: return ld(); case 0xA1: return ld();
...
}
}
```
## Known issues
* The quality of the audio emulation on Linux is very poor. Typing `export SDL_AUDIODRIVER=ALSA` before running the emulator has been reported to improve it.
## Contributors
* [AndreaOrru](https://github.com/AndreaOrru/LaiNES) - Original Author
* [Jeff Katz](https://github.com/kraln) - Mapper 002, 003, initial 007, and configuration.
* [Kevoot](https://github.com/Kevoot) - Switch port, 007 integration, threading
## References and credits
- Original by [AndreaOrru](https://github.com/AndreaOrru/LaiNES)
- Special thanks to [Ulf Magnusson](https://github.com/ulfalizer) for the invaluable [PPU diagram] (http://wiki.nesdev.com/w/images/d/d1/Ntsc_timing.png) and for his [excellent implementation](https://github.com/ulfalizer/nesalizer) which was a big source of inspiration.
- blargg's APU sound chip emulator: http://blargg.8bitalley.com/libs/audio.html#Nes_Snd_Emu
- Complete hardware reference: http://problemkaputt.de/everynes.htm
- Tick-by-tick breakdown of 6502 instructions: http://nesdev.com/6502_cpu.txt
-- For Switch version:
[TurtleP](https://github.com/TurtleP) for reference material with SDL and listening to my whining.