Skeetendo

It's some asm code that you'd have to replace/add. There's no specific tool for that. You could do it with a hex editor by translating the instruction mnemonics to opcodes but you'll run into the issue that some changes involve more space than the original so you'll need to add some messy jumps to fit all the additional instructions. That's what I had to do myself, it isn't hard at all because these are very simple edits but requires basic knowledge of assembly language and the result isn't the cleanest.

If you install the pokecrystal dissasembly and work over it instead, you'd just have to change a few instructions of the involved functions as pointed in the thread that you linked and then pokecrystal will build the rom for you.

If you don't take the pokecrystal route there was also this GB assebler tool that could make it a bit easier than doing in through hex editing. Still keep in mind that unless you somehow dissasemble the whole rom with it you'll still have to deal with the same limitations as with the hex editor, but at least you don't have to translate everything to hex.

Last edited by Crystal_ (2015-10-15 12:04:29)

The code mentioned in that thread is here.