Zapper test ROMs

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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Re: Zapper test ROMs

Post by tepples » Thu Jun 23, 2016 11:14 am

Would it work to modify the TV's LED backlight to flicker at 15.7 kHz?

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Re: Zapper test ROMs

Post by lidnariq » Thu Jun 23, 2016 11:34 am

As long as the backlight is flickering at all, and it blocks a higher enough proportion of light where it's "black" instead of bright, I think it should work. I got adequate pickup with my zapper with light frequencies of both 4kHz and 64kHz.

EDIT: I just tried hooking up my zapper to my desktop's soundcard; the trigger works fine but the photodiode sensor can't see the CCFL in my monitors.
Last edited by lidnariq on Thu Jun 23, 2016 12:57 pm, edited 1 time in total.

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Re: Zapper test ROMs

Post by rainwarrior » Thu Jun 23, 2016 12:45 pm

It seems a lot less practical to mod a TV than a zapper, though, whatever floats your boat, I guess?

In either case, you'd need new software too. There's just no easy way to make Duck Hunt great again. :(

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Re: Zapper test ROMs

Post by Great Hierophant » Thu Jun 23, 2016 2:33 pm

This might be a dumb question, but what would happen if you modified the zapper to look for a 60Hz signal instead of a 15KHz signal? The CRT draws roughly 15,750 scanlines each second or 262.5 scanlines every frame. The LCD draws the screen instantaneously 60 times per second. Zapper gun games look for black in the first frame followed by bright white in the second frame. Theoretically, it should work. Practically, I would suspect that the 60Hz transition time is too slow for the gun to give an accurate dark/light response.

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Re: Zapper test ROMs

Post by lidnariq » Thu Jun 23, 2016 2:40 pm

The demodulator can't be tuned that slow.

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Re: Zapper test ROMs

Post by qwertymodo » Thu Jun 23, 2016 3:58 pm

Think about it, at 15kHz, you get 15 cycles per ms. You need those cycles to establish a reliable signal that can be distinguished from noise. 15 cycles at 60Hz would take 250ms. And that's just for a single bit. Granted, you could probably use fewer cycles, but essentially, you are talking about a fundamentally different detection and communication protocol. There just isn't any simple way to "just do the same thing at a different clock speed" unless you can live with the 250x slowdown.

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Re: Zapper test ROMs

Post by pakosup » Sun Sep 16, 2018 1:20 am

I'm testing a hack that implements adjustable delay for light signal detection. So now it works quite fine, especially on HidefNES and RetroUSB AVS (HDMI signal has shorter delay compare to Composite video on LCD). I hope the author will release his hack soon.

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