UXNGBA

This is a port of the UXN virtual machine for the GBA. UXN is a project created by the artist collective and research studio 100 rabbits. It can be used to write small graphical applications, tools and games. Programs written for UXN are distributed via bytecode compiled roms, akin to classic console emulators. For this project, uxn roms are embedded directly in the .gba rom.

Building from source

To build this software you need the devkitPro SDK. Once installed, you may need to modify the Makefile to ensure the path is correct, but should work with the default devikit installation methods on Linux and macOS.

DEVKITPRO   := /opt/devkitpro
DEVKITBIN   := $(DEVKITPRO)/devkitARM/bin
DEVKITTOOLS := $(DEVKITPRO)/tools/bin
LIBGBA_DIR  := $(DEVKITPRO)/libgba
LIBGBA_SRC  := $(DEVKITPRO)/libgba/include/
LIBGBA      := $(LIBGBA_DIR)/lib/libgba.a
LIBGBA      += $(LIBGBA_DIR)/lib/libfat.a
LIBGBA      += $(LIBGBA_DIR)/lib/libmm.a

If everything is properly installed, you should be able to run make to compile the program into a uxngba.gba rom. If you have mgba-qt installed, you can test it with: make run.

To use a specific UXN compiled rom, you can pass it as the ROM_SRC make parameter:

make run ROM_SRC=roms/noodle.rom

If you have compiled a rom already and want to change it, you probably want to use make clean beforehand.

Configuration

The output .gba files will embed the rom used for installation. Different roms have different needs, such as the usage of different input methods or the desired audio quality. These options can be selected by defining the right macros on compile time as described below.

Input method order

Uxngba currently supports three different control schemes that can be cycled by pressing the SELECT button: CONTROL_CONTROLLER, CONTROL_MOUSE and CONTROL_KEYBOARD. To select the order and available methods set the CONTROL_METHODS macro on compile time. For example, noodle doesn't make much use of the controller scheme, and we may want to use the mouse as the default input method. This can be achieved with the following command:

make run ROM_SRC=roms/noodle.rom CONFIG="-DCONTROL_METHODS=CONTROL_MOUSE,CONTROL_KEYBOARD"

Audio quality

Audio processing can be computationally expensive and the GBA has limited resources. uxngba supports 4 audio channel devices simultaneously, and depending on the demands of the rest of the program, the audio quality can be increased or decreased. By default, sounds will play on a 18157 Hz buffer, which offers a good quality-performance compromise. A high quality and low-fi audio modes can be selected by setting the AUDIO_HIFI or AUDIO_LOFI macros:

make run ROM_SRC=roms/audio.rom CONFIG="-DAUDIO_HIFI"

  or

make run ROM_SRC=roms/audio.rom CONFIG="-DAUDIO_LOFI"

Text layer

When writing text to the screen (for example using the console device) the text will be drawn by default on the foreground layer. This can be controlled by setting the TEXT_MODE option to 0 for foreground mode or 1 for background mode.

make run CONFIG="-DTEXT_MODE=1"

Performance metrics

To enable profiling, the PROF_ENABLE macro can be used. This will display the cycle count for input handling (INPUT), loop uxn evaluation (EVAL), screen buffer flip (FLIP) and audio mixing (MIX). If PROF_ENABLE is set to 0, the current frame numbers will be displayed, if set to 1, the maximum cycle count for each section will be used instead. Enabling profiling can have a small performance impact, so these numbers may not be 100% accurate, but should give a good indication. Using PROF_SHOW_X and PROF_SHOW_Y we can control at which tile the cycle count text will be located.

make run CONFIG="-DPROF_ENABLE=0 -DPROF_SHOW_Y=8 -DPROF_SHOW_X=8"