Hacking controls in a rom.

Discussion in 'GBA - Game Development, ROM Hacks and Translations' started by askforit666, Jul 18, 2008.

Jul 18, 2008

Hacking controls in a rom. by askforit666 at 11:57 AM (1,074 Views / 0 Likes) 1 replies

  1. askforit666
    OP

    Newcomer askforit666 Newbie

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    Hi

    I got a mp4 player that can run gba games but i got a problem there's only 4 buttons and im missing the R and there is no way to change the control in the emulator.
    The game im trying to run is Zelda minish cap and without the R button i cant shrink to minish size so im stuck there.Is there a way to change the controls in the rom
    with a hex editor i would like to swap R&L.Well i hope to find someone who tried something like this and can point me out the good direction.

    Regards
     
  2. FAST6191

    Reporter FAST6191 Techromancer

    pip
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    It would probably be easier to hack/recompile the emulator (either add R and replace another button or add R by using more than one button) but you could do a rom as well.
    Although searching for MP4 player GBA emulation says it could be the JXD301 which having onboard stuff could make things harder (I am not a great fan of the idea of hacking the onboard code (MSA/blackfin assembly is not something I know a great deal about)). Post what you have and it might be possible to go that route.

    Controls work using a dedicated register for keys:
    http://www.coranac.com/tonc/text/keys.htm
    and more low level:
    http://nocash.emubase.de/gbatek.htm#gbakeypadinput

    From here you have several options.
    The register is read only, now whether it will be that way for the emulator or not is a different matter (most emulators are fairly accurate in this regard unless they have but as it stands to get an L press to write the R register probably will not happen. However while I have not hacked the game but a fair few copy the register and operate on that
    Here it would just be a case of operating on that copy, the most simple way I can see would be to abuse the sleep/soft reset hacks as they are "always on" or possibly even as a cheat with something like gabsharky.

    Get the game to think L is the button of choice.
    As mentioned a copy of the register is usually the method of choice so here a check would be done to see if R is pressed, you just alter the check to check for L or something.
     

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