[NDS] Execute an AR Code only once?

[MichiS97]

I really don't understand it, I'm using a new address now and it's the same problem: It works just fine on Desmume and not at all on the DS

221BA598 00000002
94000130 FCFE0000
A23F7750 00000001
DB000000 021BA605
D4000000 00000002
D8000000 021BA605
123F7750 00000001
D2000000 00000000

[Pyriel]

http://problemkaputt.de/gbatek.htm#dsmemorymaps

That's the range of main memory anyway. It's theoretically possible that some other addresses could be writable with the right offset and codes, but it's generally best to stick with user memory ranges unless you know what you're doing.

Although, according to this, only 3 KB of the BIOS range is actually used, so if it's writable and initialized, the unused portions would make an ideal, fixed-location code cave. Assuming you can safely branch into code there without issuing syscalls or whatever the ARM/NDS equivalent is. I'm guessing that one or more difficulties make that impossible or infeasible, otherwise people more familiar with the NDS would probably have documented how to do it.

[MichiS97]

When in doubt, just write to 0x02000000 since it's usually unused/free. If you find another spot, make sure it's between 0x02000000 and 0x02400000.

Oh so that's the memory range you can write to with AR Codes? I couldn't find that anywhere

[Demonic722]

When in doubt, just write to 0x02000000 since it's usually unused/free. If you find another spot, make sure it's between 0x02000000 and 0x02400000.

[rimsky82]

Agreed, without looking at the memory map... An emulator might allow a write to 0x2FFFFFF, but the DS hardware might not. I would run the game and look for some RAM that isn't used to store that value.

[Helder]

What's at the 3rd line's address? Seems like an odd address.

[MichiS97]

Are you properly terminating the code with the D2000000 00000000 line? also what game is it?

Yes I am, it's Legend of Zelda Phantom Hourglass

221BA598 00000002
94000130 FCFE0000
A2FFFFFE 00000001
DB000000 021BA605
D4000000 00000002
D8000000 021BA605
12FFFFFE 00000001
D2000000 00000000

I made some changes to the code, here's the updated one

[Helder]

Are you properly terminating the code with the D2000000 00000000 line? also what game is it?

[MichiS97]

Okay...now I've got a very strange problem. The code I made works flawlessly on my PC using the Desmume emulator, however, it doesn't work on my DS at all. I use a DSTWO flashcard for the game and the very same code and save file from the emulator. I really don't know what's going on here, I never had this happening before. Are there code types that are not supported by the cheat engine the DS flashcards use?

[dlevere]

static.patater.com/gbaguy/gbaasm.htm
Kenobi's GameBoy Advanced ASM Tutorial

www.coranac.com/tonc/text/asm.htm
Whirlwind Tour of ARM Assembly

http://www.codemasters-project.net/p...hp?content.202
Cursor Hacking and Advanced Tracing

[MichiS97]

Well, I'm just talking something like:

94000130 FCFF0000
6XXXXXXX 00000001
your code
0XXXXXXX 00000001

The only purpose for XXXXXXX is to ensure the code can be used just once. You could have another code tied to a different combination of buttons set the flag off. However, looking at what you're doing, it seems like the goal might be to run the increment only once each time the code is used (i.e. every time a new potion is added by it). That will probably require ASM.

Yeah I was thinking to complicatedly Thanks for your advice! I've got one last question though: Can you give me the link to a good tutorial about ASM hacking on the DS? I did some basic NES stuff in the past but nothing apart from that and I'd really like to look into it

[Pyriel]

Well, I'm just talking something like:

94000130 FCFF0000
6XXXXXXX 00000001
your code
0XXXXXXX 00000001

The only purpose for XXXXXXX is to ensure the code can be used just once. You could have another code tied to a different combination of buttons set the flag off. However, looking at what you're doing, it seems like the goal might be to run the increment only once each time the code is used (i.e. every time a new potion is added by it). That will probably require ASM.

[Demonic722]

Try something like this:

::Your Code
221BA598 00000002
[COLOR=#008000]74000100 FF00000C[/COLOR]
94000130 FCFF0000
DB000000 021BA605
D4000000 00000001
D8000000 021BA605
D2000000 00000000

That line highlighted in green slows down the execution time. If that's too fast or slow, try adjusting the value.

Note: This will not perfect the code. To ensure the code increments by exactly 1 each button press/hold, ASM is your best option.

[MichiS97]

Is there a section of memory that isn't used by the games, that is accessible to the AR, and is initialized on start up? That's the easiest way to handle something like this. Check an address there for not-equal <value> and then at the tail end of your code, set the address to that value.

I tried to do that but the problem is that I don't know how to compare to offsets. Of course, there are code types which would let me check if the value of a given offset is bigger/smaller/equal/not equal to a value that is also given by me but AFAIK you can't just compare two offsets with another

Here's the code:
221BA598 00000002 //this gives my player a potion (that already works but the potion isn't usable since the icon for it is greyed out)
94000130 FCFF0000 // simple button activator
DB000000 021BA605 //loads the value at offset 0x021BA605, which determines which icons for the potions are greyed out
D4000000 00000001 //increments the value by 1
D8000000 021BA605 // stores the value back at its address

Okay, so the code works flawlessly, if it wouldn't be for the fact that the value at 0x021BA605 mustn't be incremented more than once.

[Demonic722]

Post the code so we can look at it.