From 42c3cc0bc72efe019bf2ff7de907116b022e47c5 Mon Sep 17 00:00:00 2001
From: Steven Hugg <hugg@fasterlight.com>
Date: Wed, 16 Sep 2026 10:50:05 +0200
Subject: [PATCH] gb: better skeleton preset

---
 presets/gb/skeleton.sdcc | 91 +++++++++++++---------------------------
 1 file changed, 28 insertions(+), 63 deletions(-)

diff --git a/presets/gb/skeleton.sdcc b/presets/gb/skeleton.sdcc
index 7fa9e8bd..e05f7e14 100644
--- a/presets/gb/skeleton.sdcc
+++ b/presets/gb/skeleton.sdcc
@@ -1,78 +1,43 @@
+/*
+Hello world for Game Boy.
+Set the BG palette, write a message to the tile map,
+then turn on the LCD.
+
+Ported from presets/nes/hello.c, using GBDK (gb/gb.h).
+*/
 
 //#link "gb/sfr.sgb"
 //#link "gb/crt0.sgb"
 //#resource "gb/global.sgb"
+
 #include <stdint.h>
-#include <string.h>
 #include "gb/types.h"
 #include "gb/hardware.h"
 #include "gb/gb.h"
+#include "gbtext.h"
 
-#define NUM_TILES 46
+// main function, run after console reset
+void main(void) {
 
-static const uint8_t font[NUM_TILES*16] = {
-/*;;{w:8,h:8,bpp:1,count:46,brev:1,np:2,pofs:1,sl:2};;*/
- 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
-,0x81,0x81,0x42,0x42,0x24,0x24,0x18,0x18,0x18,0x18,0x24,0x24,0x42,0x42,0x81,0x81
-,0x00,0x00,0x24,0x24,0x00,0x00,0x00,0x00,0x24,0x24,0x18,0x18,0x00,0x00,0x00,0x00
-,0x00,0x00,0x24,0x24,0x00,0x00,0x00,0x00,0x18,0x18,0x24,0x24,0x00,0x00,0x00,0x00
-,0x00,0x00,0x36,0x36,0x49,0x49,0x41,0x41,0x22,0x22,0x14,0x14,0x08,0x08,0x00,0x00
-,0x00,0x00,0x00,0x00,0x08,0x08,0x04,0x04,0x7E,0x7E,0x04,0x04,0x08,0x08,0x00,0x00
-,0x00,0x00,0x00,0x00,0x10,0x10,0x20,0x20,0x7E,0x7E,0x20,0x20,0x10,0x10,0x00,0x00
-,0x00,0x00,0x10,0x10,0x38,0x38,0x54,0x54,0x10,0x10,0x10,0x10,0x10,0x10,0x00,0x00
-,0x00,0x00,0x10,0x10,0x10,0x10,0x10,0x10,0x54,0x54,0x38,0x38,0x10,0x10,0x00,0x00
-,0x00,0x00,0x00,0x00,0x10,0x10,0x10,0x10,0x7C,0x7C,0x10,0x10,0x10,0x10,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x1C,0x1C,0x00,0x00
-,0x00,0x00,0x06,0x06,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x02,0x02,0x04,0x04,0x08,0x08,0x10,0x10,0x1E,0x1E,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x02,0x02,0x0C,0x0C,0x02,0x02,0x02,0x02,0x1C,0x1C,0x00,0x00
-,0x00,0x00,0x12,0x12,0x12,0x12,0x1E,0x1E,0x02,0x02,0x02,0x02,0x02,0x02,0x00,0x00
-,0x00,0x00,0x1E,0x1E,0x10,0x10,0x1E,0x1E,0x02,0x02,0x02,0x02,0x1E,0x1E,0x00,0x00
-,0x00,0x00,0x0C,0x0C,0x10,0x10,0x1C,0x1C,0x12,0x12,0x12,0x12,0x0C,0x0C,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x04,0x04,0x0E,0x0E,0x04,0x04,0x04,0x04,0x04,0x04,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x22,0x22,0x1C,0x1C,0x22,0x22,0x22,0x22,0x1C,0x1C,0x00,0x00
-,0x00,0x00,0x1E,0x1E,0x12,0x12,0x1E,0x1E,0x02,0x02,0x02,0x02,0x02,0x02,0x00,0x00
-,0x00,0x00,0x18,0x18,0x24,0x24,0x3C,0x3C,0x24,0x24,0x24,0x24,0x24,0x24,0x00,0x00
-,0x00,0x00,0x38,0x38,0x24,0x24,0x38,0x38,0x24,0x24,0x24,0x24,0x38,0x38,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x1C,0x1C,0x00,0x00
-,0x00,0x00,0x38,0x38,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x38,0x38,0x00,0x00
-,0x00,0x00,0x3C,0x3C,0x20,0x20,0x38,0x38,0x20,0x20,0x20,0x20,0x3C,0x3C,0x00,0x00
-,0x00,0x00,0x3C,0x3C,0x20,0x20,0x38,0x38,0x20,0x20,0x20,0x20,0x20,0x20,0x00,0x00
-,0x00,0x00,0x18,0x18,0x20,0x20,0x2C,0x2C,0x24,0x24,0x24,0x24,0x18,0x18,0x00,0x00
-,0x00,0x00,0x24,0x24,0x24,0x24,0x3C,0x3C,0x24,0x24,0x24,0x24,0x24,0x24,0x00,0x00
-,0x00,0x00,0x38,0x38,0x10,0x10,0x10,0x10,0x10,0x10,0x10,0x10,0x38,0x38,0x00,0x00
-,0x00,0x00,0x3C,0x3C,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x38,0x38,0x00,0x00
-,0x00,0x00,0x24,0x24,0x28,0x28,0x30,0x30,0x28,0x28,0x24,0x24,0x24,0x24,0x00,0x00
-,0x00,0x00,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x38,0x38,0x00,0x00
-,0x00,0x00,0x22,0x22,0x36,0x36,0x2A,0x2A,0x22,0x22,0x22,0x22,0x22,0x22,0x00,0x00
-,0x00,0x00,0x24,0x24,0x34,0x34,0x2C,0x2C,0x24,0x24,0x24,0x24,0x24,0x24,0x00,0x00
-,0x00,0x00,0x18,0x18,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x18,0x18,0x00,0x00
-,0x00,0x00,0x38,0x38,0x24,0x24,0x38,0x38,0x20,0x20,0x20,0x20,0x20,0x20,0x00,0x00
-,0x00,0x00,0x18,0x18,0x24,0x24,0x24,0x24,0x24,0x24,0x2C,0x2C,0x1C,0x1C,0x02,0x02
-,0x00,0x00,0x38,0x38,0x24,0x24,0x38,0x38,0x24,0x24,0x24,0x24,0x24,0x24,0x00,0x00
-,0x00,0x00,0x1C,0x1C,0x20,0x20,0x18,0x18,0x04,0x04,0x04,0x04,0x38,0x38,0x00,0x00
-,0x00,0x00,0x3E,0x3E,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x00,0x00
-,0x00,0x00,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x18,0x18,0x00,0x00
-,0x00,0x00,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x14,0x14,0x08,0x08,0x00,0x00
-,0x00,0x00,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x2A,0x2A,0x14,0x14,0x00,0x00
-,0x00,0x00,0x22,0x22,0x14,0x14,0x08,0x08,0x08,0x08,0x14,0x14,0x22,0x22,0x00,0x00
-,0x00,0x00,0x22,0x22,0x14,0x14,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x00,0x00
-,0x00,0x00,0x3C,0x3C,0x04,0x04,0x08,0x08,0x10,0x10,0x20,0x20,0x3C,0x3C,0x00,0x00
-/*;;*/
-};
-
-void main(void)
-{
+  // GB can only write VRAM while the LCD is off
   DISPLAY_OFF;
-  memcpy(_VRAM8000, font, sizeof(font)); // copy tile data
-  memcpy(_SCRN0, font, 32*32); // copy garbage data to screen
-  BGP_REG = 0xe4; // palette
-  LCDC_REG = LCDCF_ON|LCDCF_BG8000|LCDCF_BG9800|LCDCF_BGON|LCDCF_OBJ16|LCDCF_OBJON|LCDCF_WIN9C00|LCDCF_WINOFF;
+
+  // background palette: color 0 = white, 1 = light, 2 = dark, 3 = black
+  BGP_REG = 0xE4;
+  OBP0_REG = OBP1_REG = 0xE4;
+
+  // copy the 8x8 font into BG tile data
+  font_init();
+
+  // write text to the tile map (tile index == ASCII code)
+  put_str(2, 2, "HELLO, WORLD!");
+
+  // enable the background layer, then the LCD
+  SHOW_BKG;
   DISPLAY_ON;
-  // Loop forever
-  while(1) {
-    // Game main loop processing goes here
-    // Done processing, yield CPU and wait for start of next frame
+
+  // infinite loop
+  while (1) {
     wait_vbl_done();
   }
 }