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Games Console
Hysenlowes Posted: 27 May 2022, 03:05 PM
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Hi all,
I'm looking to create a games console of my own this summer and I was wondering where you did your research when designing the wiring for the console as I'd like to practice designing my own circuits rather than copy your design exactly.

Thanks,
Hysen

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mit Posted: 29 May 2022, 09:05 AM
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yeah whatever

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I started with a generic development board for the ATmega chip, just so that the chip is powered, easy to load code onto, and most of the GPIO pins are on headers.

Then I kind of made it up as I went along, soldered up some DACs to drive the oscilloscope, then spent a while messing with sound hardware. If I was making it from scratch I would have wired up the DACs correctly (they're outputting negative voltages, by mistake, but now all the games are written with that in mind).

The pictures of the build on the project pages are when I re-built the console to fit in an enclosure. The original was even more messy. The cartridges plugged into a random old IDC cable. I was planning to re-build the cartridges too, along with a more appropriate connector, but didn't get round to it.

The sound hardware was based on googling for "noise generator circuit". In my original design, I was turning the noise on and off by powering the op-amp's positive rail from a GPIO pin. Can't remember why I changed that in the rebuild.

So, in answer to your question, pretty much just google I guess. I also found a copy of Horowitz and Hill, The Art of Electronics. There was a PDF of an old edition floating around, I learned most of my basic electronics from that book.

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Hysenlowes Posted: 29 May 2022, 11:05 PM
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Thanks for the reply. After re-reading your documentation, I understand your video hardware and I'm going to attempt to design something similar.

But your audio hardware I'm still a little uncertain on. Why do you need a noise circuit when you can output the square waves from the Atmega and amplify them with the opamp?



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mit Posted: 30 May 2022, 10:05 AM
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yeah whatever

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The noise channel is used for percussion.

The sound system was based on what I thought the Gameboy had, but actually the Gameboy sound hardware is much more versatile. The "noise" channel on a Gameboy is an LFSR with control over the frequency and tap position. It can make all kinds of sounds, a good example is the opening scene from Link's Awakening. It's used to make the thunder, the waves splashing on the beach, and the ka-ching noise of the sword as the title appears.

Whereas my console's noise channel can only go "sh sh sh sh sh"

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Hysenlowes Posted: 30 May 2022, 01:05 PM
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Thanks for the reply I didn't even think about percussion which is why it confused me so much.
I think I can hear the sh sh when you place a Tetris block down in your video.
I'll do some research on LFSR and see if I can implement it into my console to get more control over the percussion.

What is the oscilloscope you use in your video?




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mit Posted: 1 Jun 2022, 08:06 AM
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In the video I'm using a Hameg scope (HM604) but I developed it on a different one, I think it was one of the cheap 20MHz CRT scopes. I tried it on a digital scope a couple of times, it's usually completely unplayable, they just don't render XY mode well enough.

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