Centipede Double Cannon hack wanted!

[SoundGammon]

Been playing Centipede on the ProSystem emulator and I set it up for two-player team play.

 

Then, I set player one & player 2 controller inputs to controller one.

 

Now I move both cannons together!

 

I move immediately to the left or right so that both cannons are together and I have double the fire power!

 

Much like Galaga and a lot more fun!

 

I'd like a hack of both the regular Centipede and the Trak-Ball version to play them on a real 7800.

 

I know I can wire both controller cables into one 9-pin jack and make it work that way, but don't want to do that.

 

Can it be done?

Edited July 24, 2017 by SoundGammon

[Synthpopalooza]

Shouldn't be too hard. I wonder if any assembly code exists for this. I think it's just a matter of finding the code that reads port 1 and replacing it with port 0.

[Andromeda Stardust]

Wiring both joystick ports together in parallel is an option and should work for both the joystick and trackball variants, provided the game does not activate the bidirectional bus and attempt to talk back to the controller ports.

 

Hacking is fun too, if you have a working flash cart. You'll need to know each address in the ROM where the CPU reads the right controller port inputs and modify those values in a hex editor so that it reads the left controller port. It shouldn't require recompiling the ROM, just basic ASM hacking.

 

Seems the emulators don't need it as you can just remap the inputs. I'd like to see a video of this working on real hardware. Also be advised there are some caveats to twin fire. You become a bigger target, and your ships may become separated while navigating the mushrooms.

[Trebor]

For any interested and ambitious enough to look into the OP request...

 

Centipede Source Code:

http://www.atarimuseum.com/videogames/consoles/7800/games/

Blue Azure's Centipede Disassembly:

http://atariage.com/forums/topic/207349-centipede-7800-disassembly/

Kenfused's Trakball Hack:

http://atariage.com/forums/topic/71780-trackball-test-program-centipede-tb/?do=findComment&comment=883326

Includes one trakball sharing in a Two Player Alternating Mode.

Defender_2600 Frameless Hack:

http://atariage.com/forums/topic/239376-7800-centipede-arcade/?do=findComment&comment=3375145

Kenfused's controller and game options, with updated title screen, removes the in-game boarder frame, and updates graphics for a more authentic Arcade look.

Another, albeit more challenging hack, approach is to change an individual player's shot so it matches that of a two player simultaneous effort.

[Lynxpro]

 

For any interested and ambitious enough to look into the OP request...

 

Centipede Source Code:

http://www.atarimuseum.com/videogames/consoles/7800/games/

Blue Azure's Centipede Disassembly:

http://atariage.com/forums/topic/207349-centipede-7800-disassembly/

Kenfused's Trakball Hack:

http://atariage.com/forums/topic/71780-trackball-test-program-centipede-tb/?do=findComment&comment=883326

Includes one trakball sharing in a Two Player Alternating Mode.

Defender_2600 Frameless Hack:

http://atariage.com/forums/topic/239376-7800-centipede-arcade/?do=findComment&comment=3375145

Kenfused's controller and game options, with updated title screen, removes the in-game boarder frame, and updates graphics for a more authentic Arcade look.

Another, albeit more challenging hack, approach is to change an individual player's shot so it matches that of a two player simultaneous effort.

 

 

Doesn't Kenfused want credit if his code is used in a project?

 

And 7800 Centipede-TB can use 2 Trak-Balls in native Trak-Ball mode in the co-op settings. Joystick Jedi and I used a CX22 and a CX80 together on my copy at the Davis Atari Party last year. Well, we borrowed them. The CX80 belonged to Bill Kendrick and the CX22 was Dan Kramer's.