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Ghost button presses on IPAC4 -- bad MAME key assignments?
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Roo5676:
The question: Is there a definitive list of known "problem" keys to avoid using when setting up a keyboard encoder for use in MAME?

The details:

I have a Quad Controller from mameroom.com with an IPAC4 in it.  After getting it configured to my liking for all the different programs I run, everything seemed to work great.  Played some intense 2 player games and tested out the buttons of all 4 players individually.

I wasn't having any problems until I had my first 4-player arcade night.  Most games (X-Men, Bomberman, Power Stone 2 on DreamCast), never showed any problems that I know of, despite chaotic tapping of buttons from all four players (although it might be a bit hard to notice if there was).  But when we were playing NBA Jam, there were occasional random phantom/ghost key presses.  I would be running down the court (holding turbo) and then my guy would just jump into the air or shoot unexpectedly -- usually when someone else jumped/shot.  It's worth noting that jump and shoot are the same button.  It happened to me for awhile, then other people on and off throughout the session.  Sometimes it was fine for a bit and didn't happen to anyone.  I don't think it ever happened to player 4, just players 1-3 at different points.

I am not using any special/windows keys in my set up.  It's pretty much all letters, numbers, special characters like ";" "?", etc., and number pad numbers.  I am not using CTRL, ALT, WIN, HOME, END, PG UP, PG DN, INS, DEL, PRT SCR, PAUSE, F1-F12 etc.

Now I've read that the IPAC is not supposed to have any ghosting or maximum simultaneous key press issues.  I also had changed the buttons on NBA Jam to buttons 7, 5 and 6 to be more comfortable for that game (default MAME buttons for other games like X-Men are 1, 2, 3; PowerStone on NullDC is set for 1, 2, 4, 5).

So the big question is...Are there keyboard keys which are known to cause issues in MAME, outside of the ones mentioned above?  I've searched and searched but couldn't find a definitive list -- just topics about people accidentally hitting ALT-ENTER, etc.

Here are the keys we were using to play NBA Jam when I was seeing the phantom button presses.  Does anything jump out?  I'm a little suspicious of "[" on P4, since P4 never experienced the issue to my knowledge.  I suspect MAME because I saw no problems on Power Stone 2 on NullDC, using a lot of the same buttons.

Player 1
Joystick: (Up) (Down) (Left) (Right)
Buttons: (C) (Number Pad 5) (Z)

Player 2
Joystick: (R) (F) (D) (G)
Buttons: (/) (W) (,)

Player 3
Joystick: (I) (K) (J) (L)
Buttons: (Number Pad 6) (O) ( ; )

Player 4
Joystick: (Y) (N) (V) (U)
Buttons: (\) (M) ([)

Thanks...
vagabound:
What MAME build and what version are you using?

What is your setting for waitvsync & syncrefresh?


I normally get ghost input even in single player games, no matter what mapping, with many version of official MAME build when I try to sync the game with monitor for smooth scrolling. The only MAME build and version on Windows I found so far that gets me smooth scrolling with good sound synchronisation and without ghost input is WolfMAME.106, which is official and only MAME build allowed for setting world records at Twin Galaxies, so it makes sense to use this build if only for the reference since it has been tested quite a bit by now.
jimmy2x2x:
Driverman, Driverman can he spam? Of course he can.

newmanfamilyvlogs:
There was a thread a while back where someone's phantom presses apparently ended up being a ground wire at just the right length to act as an antenna for a nearby radio transmitter, picking up just enough RF energy to occasionally trip the sensor on the ipac.. the solution was to change the length of the ground wire (essentially changing the tuning frequency). Sometimes it's the weirdest things that end up being solutions.

The mundane answers are to inspect the switches themselves..make sure they aren't shorting out. Look for loose wires that might be swinging during gameplay.

Open up Notepad and leave it running a few hours untouched. Does anything show up? Do the same thing put wiggle your cab around a little (as if people were playing on it hard). Trigger it then? If it doesn't then  you're starting to rule out something physical as the source.

Randomly press buttons/joystick on each player, while in notepad. Do a character search for the buttons assigned to other players. Anything show up that it shouldn't? Maybe it's a wiring problem. Maybe the IPAC is damaged.
 
vagabound:

--- Quote from: cotmm68030 on July 25, 2011, 08:21:05 am ---There was a thread a while back where someone's phantom presses apparently ended up being a ground wire at just the right length to act as an antenna for a nearby radio transmitter, picking up just enough RF energy to occasionally trip the sensor on the ipac.. the solution was to change the length of the ground wire (essentially changing the tuning frequency). Sometimes it's the weirdest things that end up being solutions.

--- End quote ---

I would expect PC ports to have some threshold and minimum operational voltage above the minuscule amount that can be induced by EM radiation. What "sensor" is there on the IPAC? Are you suggesting electric current was induced in some "sensor",  in some wire going from IPAC to control panel, or along USB cable going from IPAC to computer?


It was mentioned the problem seem to manifest only with MAME, but in any case why would you think it would be the weirdest thing when all you have to do to get ghost input is to enable "syncrefresh"? What's weird is that everyone should want to have "syncrefresh" enabled if they want to have smooth scroll, so the real mystery to me is why no one seem to be aware of this very obvious bug persisting in MAME for the last ten years?

Go ahead, take the latest MAME.143, for example, and run 'Bank Panic' with default settings. Hold left or right and fire quickly with just one button, notice how input does not overflow, no ghost actions, but there is terrible tearing, waving and choppiness in the scroll. Now, run the game again but this time enable "syncrefresh", and to make it work in this version you also have to disable throttle, then try the same thing again and you should see how input lags quite a bit and after only 10-20 seconds if you let go from the controls it starts to play all by itself. Yes? No?
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