ROM Hack Creating/Extracting Cheats for ROMs

[Kyle Hyde]

Hey guys, not quite sure if this is the right section, but I'm really interested in how to actually get cheats for NDS games yourself, without depending on cheat database updates. I played around with all sorts of cheat code editors. Those are easy to understand but I just wonder how people get those cheats. I mean, I just enter the codes the right way and have my usrcheat.dat afterwards. I'd like to get those codes myself, so how do I do that? I haven't found anything in the tutorials, so hints would be appreciated.

 

[Vulpes Abnocto]

You'll probably get better and faster answers at the Cheats Forum.

 

[Kyle Hyde]

Thanks mate. Also just found this: http://gbatemp.net/topic/73394-gbatemp-rom-hacking-documentation-project-rewritten-for-2012/
In case anyone might look for this too. Sorry for posting here ;

 

[Fishaman P]

*facepalm*
Sorry, you're new, but the idea of extracting cheats is too funny.

You just watch the memory, and the codes modify the memory.
So, you find where your health is stored, then use an activator to set it to 100 (0x63), for example.

 

[Kyle Hyde]

I understand my view on the things was weird ;P
However after just reading that part of the ROM hacking guide I already know much more. At least I know what's going on there now. I understand the concept of modifying memory. I just didn't know where to start looking ;P

 

[FAST6191]

Edit must press refresh.
To answer the "where to start" you don't- you find what you want (say infinite ammo) and then initialise the search, do as little as possible in the game but fire a bullet and see what decreased/changed, fire another and the things that changed from the first will be scanned again. You can try different types of searches that might narrow it down more quickly (ammo is probably not going to be a 64 bit or float value so no need to search like that) but that is pretty much it. If you have problems with something specific that is usually the sort of thing to ask a question on. Oh yeah you might also want to try remaking a cheat someone else made as that will hopefully ensure you are not trying to learn on an incredibly hard to hack game (it has happened in the past- usually when people pick pokemon).

The cheats forum covers a lot of it and a lot of what happens when things get more tricky; infinite health/lives, ammo and to a lesser extent time cheats are pretty easy to make for the most part but the really nice ones like experience multipliers, sometimes item related stuff and moon jump cheats use skills more commonly seen in high end ROM hacking. I have a tiny section in the PDF version of my hacking docs (stickied in this section and in my signature)

http://cheats.gbatemp.net/hack/hacking_nds.html covers the basic idea as well. Some of the tools are a bit out of date but the ideas remain the same (they remain the same on every system really)

In words games hold everything in memory as far as what ammo, health and such that you have and then better emulators or tools that attach to them will allow you to do various types of scans to see what changed (or indeed what remained the same) between you doing things in the game. Once you know what memory sections are doing what then cheat devices and cheat engines then allow various types of things to be done to the memory (most commonly they hold the value at a constant where before it might have decreased).
The more advanced cheats either deal with anti cheat (or things that trouble cheats) or recognise that the actual code that makes up the game is found in memory and edit that (back in the day this was game genie type cheats but the DS has it in memory where it can be edited).