NES Zapper vs Revolver on PC10

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oRBIT2002
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NES Zapper vs Revolver on PC10

Post by oRBIT2002 »

I've coded a patch to run VS Duck Hunt on a Standard NES/Famicom. Seems to work but I'm getting reports about the Revolver running on a PC10 working differently.
Running the patch on a NES triggers the shot when the trigger is halfway pushed on the Zapper, works as it should. But it seems with the revolver, it seems it shots when the trigger is released.
The issue cannot be reproduced on other commercial games (except for one other title).
Does anyone have any ideas about this behaviour and how I could deal with it perhaps?
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Quietust
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Re: NES Zapper vs Revolver on PC10

Post by Quietust »

oRBIT2002 wrote: Sun Jul 10, 2022 11:24 am Running the patch on a NES triggers the shot when the trigger is halfway pushed on the Zapper, works as it should. But it seems with the revolver, it seems it shots when the trigger is released.
As stated on the wiki:
The official Zapper's trigger returns 0 while the trigger is fully open, 1 while it is halfway in, and 0 again after it has been pulled all the way to where it goes clunk. The large capacitor (10µF) inside the Zapper when combined with the 10kΩ pullup inside the console means that it will take approximately 100ms to change to "released" after the trigger has been fully pulled.

Some clone zappers, like the Tomee Zapp Gun implement a simpler switch that returns 1 while the trigger is not pulled, and 0 when it is pulled. This works with most existing zapper games which usually fire on a transition from 1 to 0.
However, it appears that the Vs. Zapper games instead watch for a rising edge on the trigger, which means you'll have to patch them further in order to work with a normal light gun.
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.
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oRBIT2002
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Re: NES Zapper vs Revolver on PC10

Post by oRBIT2002 »

So it's not just about detecting trigger/sense-bits anymore, it's in the code of the game aswell then.
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