Your first program

In this chapter, you're going to learn the basics of compiling and testing a homebrew project targetting the WonderSwan.

First, set up a new project:

$ mkdir first-program/ # (1)!
$ wf-wswantool project new first-program/ # (2)!

1. Create the directory “first-program” in the terminal's current working directory.
2. Create a new wswan target project with the directory and name “first-program”.

Next, compile it:

$ cd first-program/
$ make

The build script will output lines similar to the following:

CC      src/main.c
LD      build/first-program_stage1.elf
ROM     first-program.wsc
MERGE   compile_commands.json

1. The C compiler is compiling the source file src/main.c.
2. The ELF file build/first-program_stage1.elf is being linked. This file will contain all of the program's source code and assets, but not yet placed in the console's ROM and RAM.
3. The ROM file first-program.wsc is being created, now with the correct memory placements.
4. The compile_commands.json file is being generated. This is used by your IDE to provide syntax highlighting; as a consequence, it is a good idea to run `make` after adding a new .c file to the project.

Finally, you can run the ROM file using your emulator of choice.

The program is not displaying anything - after all, there's no code written yet!

Let's examine the src/main.c file:

// SPDX-License-Identifier: CC0-1.0
//
// SPDX-FileContributor: Adrian "asie" Siekierka, 2023
// (1)!
#include <wonderful.h> // (2)!
#include <ws.h> // (3)!

void main(void) {
    while(1);
}

1. The default copyright header for the template file. This is required to inform you that you can use the example code contained therein without restrictions. However, before writing your own code, if you wish to put different terms on your code, you should remove it.
2. The wonderful.h include contains common CPU/target definitions. It's a good idea to put it in essentially every C file.
3. The ws.h include contains hardware definitions specific to the WonderSwan, as well as many lower-level hardware abstraction functions.

With only an infinite loop in main, it's clear that the code won't do anything. Let's make it do something!

For now, we're going to assume a “mono” program - we'll introduce the color mode in a later chapter. On the “mono” WonderSwan, the palette pipeline that converts tile information to display shades consists of two parts: the palette, mapping each of the four possible palette indexes to one of eight color values; and a shade look-up table, mapping each of the color values to one of the sixteen total shades which the panel can display.

First, we need to initialize the shade look-up table. At the beginning of main, add the following function call:

ws_display_set_shade_lut(WS_DISPLAY_SHADE_LUT_DEFAULT);

This sets a default shade look-up table, with the color value 0 corresponding to the brightest shade (0) and 7 to the darkest shade (15).

Next, we need to enable the display. We're going to enable the “screen 1” layer - as the WonderSwan's memory is zeroed by default, this should not cause anything to be drawn to the screen, but will enable viewing the background color - which, by default, is the first of eight color values:

outportw(WS_DISPLAY_CTRL_PORT, WS_DISPLAY_CTRL_SCR1_ENABLE);

Finally, we're going to do some changes to the display. Edit the while(1) loop as follows to cycle the first palette:

while (1) {
    outportw(WS_SCR_PAL_0_PORT, inportw(WS_SCR_PAL_0_PORT) + 1); // (1)!
    ws_delay_ms(1000); // (2)!
}

1. This loads the first palette, adds one to it, and saves it. As the lowest bits constitute the color value for the first palette index, this will cause the background color to change on every execution.
2. As we don't have any interrupts set up yet, the only thing we can do is busy-wait - that is, stall the CPU for a specified number of milliseconds.

That's all! Compile the code using make and run it in your emulator of choice. If done correctly, you should see the display slowly change colors from brightest to darkest and back again.