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Topics - Whipon

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I'm trying to do a simple ASM hack to the GBA game Castlevania - Harmony of Dissonance.

I want to be able to change weapons each time I use a potion, high potion or elixir.

My first approach was to just replace some of the code involved in using these items:

(NOTE: Opcodes are reversed, as they are stored that way in the ROM).

Code: [Select]

8242 2ED2 0125 D888 1018 0880 => A07B 0130 0728 00D1 0120 A073

7BA0 LDRB R0, [R4 + #0e]
3001 ADD R0, 01
2807 CMP R0, 07
D100 BNE 000001a6 (00)
2001 MOV R0, 01
73A0 STRB R0, [R4 + #0e]

I did the above hack several years ago and worked very well. This time I wanted to keep the original code and jump to a sub routine instead.

I found lots of free space at the offset 080DADA4.

So I wanted to insert a BL at offset 0802974E

Code: [Select]
I had to modify the opcode since it made No$GBA to stop because the one I used with VBA was read as invalid. I don't understand why.

0A88 E08A => B1F0 29FB (F0B1 FB29 BL 080DADA4) (No$GBA) - B1F0 29DB (F0B1 DB29) (VBA)


7BA0 LDRB R0, [R4 + #0e]
3001 ADD R0, 01
2807 CMP R0, 07
D100 BNE 000001a6 (00)
2001 MOV R0, 01
73A0 STRB R0, [R4 + #0e]
0A88    LDRH R2, [R1, #000] (Replaced instruction at 0802974E)
E08A    LDRH R0, [R4, #016] (Replaced instruction at 08029750)
7047    BX R14 (Return to 8029752)

The problem I'm facing is that the jump never happens. It just continues execution at next instruction (8029752).

I tried looking for help in several documents I found in the web, with no luck. I can't figure what I'm doing wrong.

Also I searched in several trace text files, in hope to find if I'm missing some opcodes, but it seems that's not the issue.

I wanted to learn how to jump and return from subroutines to improve my GBA hacking skills.

I'll really appreciate if somebody can lend me a hand.

Thanks in advance ;).


ROM Hacking Discussion / Castlevania (PRG 1) Mapper Change
« on: October 29, 2019, 10:03:42 pm »
Hello, good night!.

Recently I played some Castlevania hacks I had in my collection that I downloaded from this site.
Between those hacks, I have Castlevania - The Holy Relics, by Optomon.
I must say he made an excellent work. But sadly its not compatible with NaOH Improved Controls hack.
I managed to integrate this last hack in several Castlevania hacks, because there is free rom space avalaible. But The Holy Relics has almost all empty space used.

Then I tought about using one of the mapper hacks already avalaible:

That would increase the avalaible space. But I cannot use any of them, because Optomon's hack uses the PRG 1 rom, and these mapper hacks are for PRG 0.

I will really appreciate any help. I have a good 6502 asm understanding, but mapper change hacks are something that I find very difficult.

Regards ;).


ROM Hacking Discussion / Found a bug in Final Fantasy III Refurbished
« on: February 09, 2019, 02:53:21 pm »
Hello to everyone!.

Recently I finished Final Fantasy III Refurbished
Great translation. I enjoyed it as it was the first time I played the game.
However I found a bug in it, that prevents the use of a very cool spell.

If your class is Summoner or Sage you can cast the most powerfull summoning spells. The spell "Catastro" that summons Odin in these cases causes some screen glitches and a severe slowdown when is successful. At first I feared the game crashed but tried it several times and the game continued normally.

It would be great if this bug can be resolved, since this is one of the most powerfull spells in the game.
I'll really appreciate any help or advice to fix it.

Thanks in advance ;).

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