fixed MBC1+ROM larger bigger than 1MB

example/kid_dracula/settings.asm → examples/kid_dracula/settings.asm

@@ -26,6 +26,19 @@ DEF BANK0_FREE_SPACE EQU $3fd0
 
 
 
+; MBC type
+; --------
+; (see more here: https://gbdev.io/pandocs/MBCs.html)
+; MBC needs to be here specified in these special cases:
+; - MBC1 + expanded ROM to 1Mb or bigger (Zelda Link's Awakening [non-DX])
+; - (to-do!) MBC5 + expanded ROM to 8Mb
+; other cases will just ignore this value
+; keep in mind that, in these special cases, the hook subroutine will grow
+; from 16 bytes to 25 bytes!
+DEF MBC EQU 5
+
+
+
 ; NEW CODE LOCATION
 ; -----------------
 ; We need an empty bank to store all new code plus border data, which will be
@@ -37,8 +50,8 @@ DEF BANK0_FREE_SPACE EQU $3fd0
 ; - 64kb   --> bank $04
 ; - 128kb  --> bank $08
 ; - 256kb  --> bank $10
-; - 512kb  --> bank $20
-; - 1024kb --> bank $40
+; - 512kb  --> bank $21 (bank $20 needs more code to be accessed in MBC1)
+; - 1024kb --> bank $41 (bank $40 needs more code to be accessed in MBC1)
 DEF SGB_CODE_BANK EQU $10
 
 

examples/zelda_links_awakening/settings.asm

@@ -0,0 +1,71 @@
+; ------------------------------------------------------------------------------
+;         Super Game Boy border injector for Zelda Link's Awakening (non-DX)
+;                             by Marc Robledo 2024
+;
+;   More info at https://github.com/marcrobledo/super-game-boy-border-injector
+; ------------------------------------------------------------------------------
+
+
+
+; GAME BOOT OFFSET
+; ----------------
+; Put here the game's boot jp offset found in in $0101.
+; Usually $0150, but could be different depending on game.
+DEF GAME_BOOT_OFFSET EQU $0150
+
+
+
+; BANK 0 ROM FREE SPACE
+; ---------------------
+; 16 bytes in bank 0 are needed for the game's boot hook subroutine.
+; Hopefully, there should be enough space at the end of bank 0 or in the
+; interruption or rst vector ($0000-$00ff).
+; In the worst scenario, you will need to carefully move some code/data to
+; other banks.
+DEF BANK0_FREE_SPACE EQU $0005
+
+
+
+; MBC type
+; --------
+; (see more here: https://gbdev.io/pandocs/MBCs.html)
+; MBC needs to be here specified in these special cases:
+; - MBC1 + expanded ROM to 1Mb or bigger (Zelda Link's Awakening [non-DX])
+; - (to-do!) MBC5 + expanded ROM to 8Mb
+; other cases will just ignore this value
+; keep in mind that, in these special cases, the hook subroutine will grow
+; from 16 bytes to 25 bytes!
+DEF MBC EQU 1
+
+
+
+; NEW CODE LOCATION
+; -----------------
+; We need an empty bank to store all new code plus border data, which will be
+; quite big.
+; If the game has no empty bank, just use a bank higher than the original
+; game's bank number, RGBDS will expand the ROM and fix the header.
+; Safe bank numbers, depending on original game's ROM size:
+; - 32kb   --> impossible to do it without changing MBC
+; - 64kb   --> bank $04
+; - 128kb  --> bank $08
+; - 256kb  --> bank $10
+; - 512kb  --> bank $21 (bank $20 needs more code to be accessed in MBC1)
+; - 1024kb --> bank $41 (bank $40 needs more code to be accessed in MBC1)
+DEF SGB_CODE_BANK EQU $21
+
+
+
+; CUSTOM GB PALETTE
+; -----------------
+; set CUSTOM_GB_PALETTE_ENABLED to 1 if you want a custom GB palette for the
+; entire game screen
+; colors are RGB15 which means RGB components can go from 0 up to 31
+; warning: even if set to 0, do not delete BUILD_CUSTOM_GB_PALETTE macro!
+DEF CUSTOM_GB_PALETTE_ENABLED EQU 1
+MACRO BUILD_CUSTOM_GB_PALETTE
+    RGB 27, 30, 25	;color 0 (light)
+    RGB 17, 23, 14	;color 1
+    RGB 6, 13, 10	;color 2
+    RGB 1, 3, 4		;color 3 (dark)
+ENDM

index.html

@@ -106,7 +106,7 @@ <h1 class="hide">Super Game Boy Border Injector</h1>
 
 
 <footer>
-	Super Game Boy Border Injector v0.2<br/>
+	Super Game Boy Border Injector v0.3<br/>
 	made with <span class="love" title="Super love">Super <img src="web-injector/assets/octicon_heart.svg" alt="love" class="octicon" /></span> by <a href="https://www.marcrobledo.com" target="_blank">Marc Robledo</a>
 	<img src="web-injector/assets/octicon_github.svg" alt="GitHub logo" class="octicon" /> <a href="https://github.com/marcrobledo/super-game-boy-border-injector/"  target="_blank">See sourcecode in GitHub</a>
 </footer>

src/main.asm

@@ -42,9 +42,19 @@ boot_hook:
 	ld		a, BANK(sgb_init)
 	ld		[rROMB0], a
 
+	IF MBC == 1 && SGB_CODE_BANK>=$20
+		ld		a, ((BANK(sgb_init) & %01100000) >> 5)
+		ld		[rRAMB], a
+	ENDC
+
 	call	sgb_init
 
 	ld		[rROMB0], a
+	IF MBC == 1 && SGB_CODE_BANK>=$20
+		xor		a
+		ld		[rRAMB], a
+	ENDC
+
 	pop		af
 	jp		boot_original
 

src/settings.asm

@@ -26,6 +26,19 @@ DEF BANK0_FREE_SPACE EQU $3ff0
 
 
 
+; MBC type
+; --------
+; (see more here: https://gbdev.io/pandocs/MBCs.html)
+; MBC needs to be here specified in these special cases:
+; - MBC1 + expanded ROM to 1Mb or bigger (Zelda Link's Awakening [non-DX])
+; - (to-do!) MBC5 + expanded ROM to 8Mb
+; other cases will just ignore this value
+; keep in mind that, in these special cases, the hook subroutine will grow
+; from 16 bytes to 25 bytes!
+DEF MBC EQU 5
+
+
+
 ; NEW CODE LOCATION
 ; -----------------
 ; We need an empty bank to store all new code plus border data, which will be
@@ -37,9 +50,9 @@ DEF BANK0_FREE_SPACE EQU $3ff0
 ; - 64kb   --> bank $04
 ; - 128kb  --> bank $08
 ; - 256kb  --> bank $10
-; - 512kb  --> bank $20
-; - 1024kb --> bank $40
-DEF SGB_CODE_BANK EQU $20
+; - 512kb  --> bank $21 (bank $20 needs more code to be accessed in MBC1)
+; - 1024kb --> bank $41 (bank $40 needs more code to be accessed in MBC1)
+DEF SGB_CODE_BANK EQU $21
 
 
 

web-injector/app/assembled-code.js

@@ -1,16 +1,41 @@
-export const ASSEMBLED_HOOK=[
-	0xf5,					//push	af
-	0x3e, 'bank_number',	//ld	a, sgb_init_bank
-	0xea, 0x00, 0x20,		//ld	[0x2000], a
-	0xcd, 0x00, 0x40,		//call	0x4000
-	0xea, 0x00, 0x20,		//ld	[0x2000], a
-	0xf1,					//pop	af
-	0xc3, 'entry_point_low', 'entry_point_high' //jp original_entry_point
+export const ASSEMBLED_HOOK_INFO=[
+	//common case
+	{
+		code:[
+			0xf5,						//push	af
+			0x3e, 'rom_bank_number',	//ld	a, sgb_init_bank
+			0xea, 0x00, 0x20,			//ld	[0x2000], a
+			0xcd, 0x00, 0x40,			//call	0x4000
+			0xea, 0x00, 0x20,			//ld	[0x2000], a
+			0xf1,						//pop	af
+			0xc3, 'entry_point_low', 'entry_point_high' //jp original_entry_point
+		]
+	},
+	//MBC1 + larger than 512kb
+	//requires additional code to write to $4000 (ROM bank upper bits)
+	{
+		code:[
+			0xf5,								//push	af
+			0x3e, 'rom_bank_number',			//ld	a, sgb_init_bank_lowerbits
+			0xea, 0x00, 0x20,					//ld	[0x2000], a
+			0x3e, 'rom_bank_number_upperbits',	//ld	a, sgb_init_bank_upperbits
+			0xea, 0x00, 0x40,					//ld	[0x4000], a
+			0xcd, 0x00, 0x40,					//call	0x4000
+			0xea, 0x00, 0x20,					//ld	[0x2000], a
+			0xaf,								//xor	a
+			0xea, 0x00, 0x40,					//ld	[0x4000], a
+			0xf1,								//pop	af
+			0xc3, 'entry_point_low', 'entry_point_high' //jp original_entry_point
+		]
+	}
 ];
-
-
-export const ASSEMBLED_HOOK_BANK_NUMBER=ASSEMBLED_HOOK.indexOf('bank_number');
-export const ASSEMBLED_HOOK_ENTRY_POINT=ASSEMBLED_HOOK.indexOf('entry_point_low');
+ASSEMBLED_HOOK_INFO.forEach(function(assembledInfo){
+	assembledInfo.patchOffsets={
+		romBankNumber: assembledInfo.code.indexOf('rom_bank_number'),
+		romBankNumberUpperbits: assembledInfo.code.indexOf('rom_bank_number_upperbits'),
+		entryPoint: assembledInfo.code.indexOf('entry_point_low')
+	}
+});
 
 // assembled code from "SGB Bank - Code" SECTION in main.asm
 export const ASSEMBLED_SGB_CODE=[

web-injector/app/main.js

@@ -1,7 +1,7 @@
 import { FileParser } from './gb-parser.js'
 import { PaletteGB, PaletteSNES, ColorRGB15, Tile4BPP, MapSNES } from './console-graphics.js'
 import { EXAMPLE_GB_TILE_DATA, EXAMPLE_GB_MAP_DATA, SGB_DEFAULT_PALETTE } from './preview-example-data.js'
-import { ASSEMBLED_HOOK, ASSEMBLED_HOOK_BANK_NUMBER, ASSEMBLED_HOOK_ENTRY_POINT, ASSEMBLED_SGB_CODE } from './assembled-code.js'
+import { ASSEMBLED_HOOK_INFO, ASSEMBLED_SGB_CODE } from './assembled-code.js'
 
 
 /*
@@ -25,6 +25,7 @@ var pickerStatus={
 };
 var bufferedFiles={};
 var currentRomName;
+var currentRomType;
 
 function setPickerStatus(id, status, message){
 	pickerStatus[id]=status;
@@ -218,7 +219,8 @@ function checkFileRom(file){
 	var result={
 		supported:false,
 		title:'Invalid or incompatible Game Boy ROM',
-		banks: nBanks
+		mbc:0,
+		banks: 0
 	}
 
 	try{
@@ -248,7 +250,9 @@ function checkFileRom(file){
 		for(var i=0; i<CARTRIDGE_TYPES.length; i++){
 			if(CARTRIDGE_TYPES[i].id===byteType){
 				result.supported=CARTRIDGE_TYPES[i].supported;
+				result.mbc=CARTRIDGE_TYPES[i].mbc;
 				result.title=CARTRIDGE_TYPES[i].title;
+				result.banks=nBanks;
 				break;
 			}
 		}
@@ -257,6 +261,7 @@ function checkFileRom(file){
 		if(!result.supported){
 			throw new Error(message);
 		}
+		currentRomType=result;
 
 		var fileSize=nBanks*16384;
 		if((fileSize / 1048576) < 1)
@@ -340,10 +345,13 @@ function checkFileSGB(file){
 
 
 
-function findRepeatBytes(file, offset, len){
+function buildRepeatData(len, data){
+	return Array(len).fill(data);
+}
+function findRepeatBytes(file, offset, len, repeatMany){
 	file.seek(offset);
 	var b=file.readByte();
-	return findBytes(file, {offset:file.getOffset(), len:1, data:Array(len - 1).fill(b), reverse: false});
+	return findBytes(file, {offset:file.getOffset(), len:repeatMany || 1, data:buildRepeatData(len -1, b), reverse: false});
 }
 
 function findBytes(file, obj){
@@ -372,12 +380,6 @@ function findBytes(file, obj){
 	return null;
 }
 
-// places the injector will look for free space
-const VALID_BANK0_FREE_SPACE=[
-	{offset:0x4000, len:0x80, data:[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff], reverse: true},
-	{offset:0x0000, len:0xf0, data:[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff], reverse: false},
-	{offset:0x0000, len:0xf0, data:[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], reverse: false}
-];
 
 
 
@@ -388,15 +390,10 @@ function buildROM(){
 		rom.seek(0x0101);
 		if(rom.readByte()!==0xc3) //jp
 			throw new Error('Game has no jp entry point');
-
-		var freeSpace0=null;
-		for(var i=0; i<VALID_BANK0_FREE_SPACE.length && freeSpace0===null; i++){
-			freeSpace0=findBytes(rom, VALID_BANK0_FREE_SPACE[i]);
-		}
-		if(freeSpace0===null)
-			throw new Error('Bank 0 has no free space');
 
-		console.log('free space found in bank 0: $'+freeSpace0.toString(16));
+
+
+		//search a free bank, expand rom if needed
 		var freeBankX=null;
 		for(var i=0x4000; i<rom.length() && !freeBankX; i+=0x4000){
 			if(findRepeatBytes(rom, i, 0x4000)){
@@ -426,6 +423,36 @@ function buildROM(){
 			rom.seek(0x0148);
 			rom.writeByte(Math.log2(nBanks) - 1);
 		}
+
+
+		var assembledHookInfo;
+		if(currentRomType.mbc===1 && freeBankX>=0x20){
+			console.log('using assembled code for MBC1+ROM bigger than 1MB');
+			if(freeBankX===0x20 || freeBankX===0x40 || freeBankX===0x60){
+				//banks $20, $40, $60 need additional code to be accesed
+				//use $21, $41 or $61 instead
+				freeBankX++;
+			}
+
+			assembledHookInfo=ASSEMBLED_HOOK_INFO[1];
+		}else{
+			console.log('using common assembled code');
+			assembledHookInfo=ASSEMBLED_HOOK_INFO[0];
+		}
+
+
+		//find free space in bank 0
+		var freeSpace0=findBytes(rom, {offset:0x4000, len:0x80, data:buildRepeatData(assembledHookInfo.code.length, 0xff), reverse: true});
+		if(freeSpace0===null)
+			freeSpace0=findBytes(rom, {offset:0x0000, len:0xf0, data:buildRepeatData(assembledHookInfo.code.length, 0xff), reverse: false});
+		if(freeSpace0===null)
+			freeSpace0=findBytes(rom, {offset:0x0000, len:0xf0, data:buildRepeatData(assembledHookInfo.code.length, 0x00), reverse: false});
+
+		if(freeSpace0===null)
+			throw new Error('Bank 0 has no free space (need '+assembledHookInfo.code.length+' bytes)');
+
+		console.log('free space found in bank 0: $'+freeSpace0.toString(16));
+
 
 
 		//add SGB flags to header
@@ -442,10 +469,13 @@ function buildROM(){
 
 		//patch entry point hook
 		rom.seek(freeSpace0);
-		ASSEMBLED_HOOK[ASSEMBLED_HOOK_BANK_NUMBER]=freeBankX;
-		ASSEMBLED_HOOK[ASSEMBLED_HOOK_ENTRY_POINT]=originalEntryPoint & 0xff;
-		ASSEMBLED_HOOK[ASSEMBLED_HOOK_ENTRY_POINT + 1]=(originalEntryPoint >> 8) & 0xff;
-		rom.writeBytes(ASSEMBLED_HOOK);
+		assembledHookInfo.code[assembledHookInfo.patchOffsets.romBankNumber]=freeBankX;
+		assembledHookInfo.code[assembledHookInfo.patchOffsets.entryPoint]=originalEntryPoint & 0xff;
+		assembledHookInfo.code[assembledHookInfo.patchOffsets.entryPoint + 1]=(originalEntryPoint >> 8) & 0xff;
+		if(assembledHookInfo===ASSEMBLED_HOOK_INFO[1]){ //MBC1+1MB
+			assembledHookInfo.code[assembledHookInfo.patchOffsets.romBankNumberUpperbits]=(freeBankX & 0b01100000) >> 5;
+		}
+		rom.writeBytes(assembledHookInfo.code);
 
 		//write SGB code
 		rom.seek(freeBankX * 0x4000);
@@ -496,7 +526,7 @@ function buildROM(){
 		rom.writeByte(newChecksum & 0xff);
 
 
-		var newRomName=currentRomName.replace(/\.(gbc?)$/, ' (SGB Compatible).$1');
+		var newRomName=currentRomName.replace(/\.(gbc?)$/, ' (SGB Enhanced).$1');
 		var blob=new Blob([rom.getBuffer()], {type: 'application/octet-stream'});
 		saveAs(blob, newRomName);