ROM Hack [Help] How to make a save editor for 3ds games?

[Princess Emily]

Hi guys? Can anybody tutor me how to make a save editor? I wanna make one for Etrian Odyssey Untold because there's not one yet.
What resources/programs should I get?

For now I have a 3ds with homebrew. What else do I need?

 

[Princess Emily]

Up

 

[DarkIrata]

You should know a programming language.
• C# is a easy to use language for this. (Use any IDE you like)
• A HEX File reader like HXD to find the differences.
• Any way to dumb the Save from the Game.
• MUCH.. MUUHUUHUUCH patience.

// Wubs. posted to soon.

1. Start Game, find the value you want to edit.
2. Dumb your save.
3. Start Game, change value, save.
4. Dumb your save.
5. *Repeat to get a faster result (unnecessary)
6. Look for the position in the save dumb (OFFSET) of the value.
7. Make it possible to change value by your C# Application
8. ???
9. PROFIT

 

[vozer]

You have to learn how to decrypt and encrypt your game save first

 

[Princess Emily]

You should know a programming language.
• C# is a easy to use language for this. (Use any IDE you like)
• A HEX File reader like HXD to find the differences.
• Any way to dumb the Save from the Game.
• MUCH.. MUUHUUHUUCH patience.

// Wubs. posted to soon.

1. Start Game, find the value you want to edit.
2. Dumb your save.
3. Start Game, change value, save.
4. Dumb your save.
5. *Repeat to get a faster result (unnecessary)
6. Look for the position in the save dumb (OFFSET) of the value.
7. Make it possible to change value by your C# Application
8. ???
9. PROFIT

Dumb my save? Do you mean dump?

 

[DarkIrata]

Dumb my save? Do you mean dump?

oh yeah sorry, should't write at work.

 

[acea]

If you just want to edit the save file, all you need to do is dump a few savefiles with variations in the interested parameter only, then find the offset.

Based on save file I have and what I remember from the game,
Character data: 18C and on (starting with Fafnir); skills are lumped somewhere in the mid-end and retire/level information is near the end from what I can gather
Ingredients: A6E5-A73F (all of the ingredients are lumped together; set everything to 63 to make all 99)
Grimoires: 2770-758F (length = 32; beginning is misc. info like traded, etc followed by name, and actual add-on/skill/level are at the end).

So on and so forth. If you can write a program to find the offsets and edit the value, that's the editor right there. Finding what value is what is more or less a trial-and-error. 3DS-native hex editor may be easier to find those.