gbaid 0.2.0-alpha

GBAiD

GBAiD stands for <strong>G</strong>ame<strong>B</strong>oy <strong>A</strong>dvance <strong>i</strong>n <strong>D</strong>. I've started this project as an effort to learn the D programming language.

This emulator is written mostly in pure D, with some inline x86 (32 and 64 bit) assembly in the display emulation to help with performance.

Current state

All of the GameBoy's built-in hardware has been implemented, with the exception of sound.

I've tested 8 games so far:

• Super Mario Advance
• Mario kart
• Pokemon Emerald
• Legend of Zelda: A Link To The Past
• Legend of Zelda: Minish Cap
• Doom
• Classic NES Series: Super Mario Bros
• Classic NES Series: Metroid
• Street Fighter Alpha 3

The Classic NES Series games load, but are very glitchy. Considering the anti-emulation features implemented in them, just the fact that they load is a good thing.

The emulator uses under 40% CPU on an Intel Core i7-4980HQ (2.80GHz), for a single core.

Building

Dependencies

GBAiD uses SDL2 for input, OpenGL graphics, sound (eventually) and controller support.

• SDL 2.0.3 or greater is required
• OpenGL 2.0 or greater is required

Compiling

A D compiler and DUB should be installed. Compiling works with LDC and DMD, other compilers have not been tested.

Then use:

dub build --build release

It is necessary to build in release mode to have the performance required for the emulator to run at full speed.

LDC has better performance over DMD, use the --compiler ldc2 option to enable it.

Running

Use:

dub run --build release -- (arguments)

Again, use --compiler ldc2 option to enable LDC.

Or get the binary from the bin folder after building and use:

./gbaid (arguments)

Arguments

At minimum, you must specify the path to the bios and rom images with

-b (path to bios) (path to rom)

The following arguments are also recognized:

Long form	Short form	Argument	Usage
--bios	-b	Path to bios	Specify bios image
--save	-s	Path to save	Specify path for loading and saving saves
--noload	-n	None	Don't load the save
--nosave	-N	None	Don't save the save
--scale	-r	Scaling factor (float)	Draw the display at "factor" times the original resolution
--filtering	-f	LINEAR or NONE	What technique to use to filter the output texture to be drawn to the screen
--upscaling	-u	EPX, XBR, BICUBIC or NONE	What technique to use to increase the resolution of the drawn texture
--controller	-c	None	Disable keyboard input and use a controller instead
--memory	-m	See saves section	What memory configuration to use for the save format

Note that these arguments are case sensitive and that bundling is only supported by the noload and nosave switches.

Saves

Saves use a custom format and .gsf extension that is not compatible with other emulators. If no save path is specified, the same path as the ROM is used, but with the .gsf extension instead of whatever the ROM image is using. If no save is found matching either the given or default path, then a new save is created using that path. Saves are overwritten on exit, unless the --nosave argument is used.

The emulator can almost always auto-detect the save type, but for some games, such as the Classic NES Series, this will not work. Instead, the --memory flag should be used, with one of the arguments from below.

Argument	Description
SRAM	64K of static RAM
SRAM_EEPROM	64K of static RAM and an EEPROM
FLASH64K	64K of Flash
FLASH64K_EEPROM	64K of Flash and an EEPROM
FLASH128K	128K of Flash
FLASH128K_EEPROM	128K of Flash and an EEPROM
EEPROM	Only an EEPROM
AUTO	Auto-detect, default

For Classic NES Series games, use EEPROM

These flags are only needed when creating a new save, after that the format is saved in the save file.

Controls

These will be re-mapable in a future version.

Gamepad	Keyboard	Controller
A	P	A
B	L	B
Up	W	D-pad or L-stick
Down	S	D-pad or L-stick
Right	D	D-pad or L-stick
Left	A	D-pad or L-stick
R	R-shift	RB or RT
L	L-shift	LB or LT
Start	Enter	Start
Select	Tab	Select

Upscaling

All upscaling is implemented as OpenGL shaders.

• EPX is a simple but fast 2x upscaler.
• XBR is a 5x implementation, it gives better results, but is slower.
• BICUBIC is an interpolation method that offers better results than linear filtering at a greater cost. It upscales to whatever is defined by the --scale switch so it should always be used with this method.

When you use the --upscaling switch you should also use the --scale switch with the appropriate factor for the selected algorithm.

License

GBAiD is licensed under MIT

Useful information

This page for a whole lot of detailed information on the hardware.

This and this for a list of all instructions supported by the ARM7TDMI CPU.