Author Topic: SNES/Megadrive adapter  (Read 3173 times)

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Offline bluefoxicy

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SNES/Megadrive adapter
« on: November 05, 2019, 01:29 AM »
The N8 has a 72-pin connector. SNES has 62 pins.  Megadrive has 64.

It should be possible to:

  • Ground various pins on short connectors, detect that, and identify that you're on an SNES or Megadrive
  • Load up an SNES or Megadrive firmware if connected (via adapter) to such a console
  • Worst case, detect and then notate who the console is; upon reset, load correct firmware

From what I can tell, the Everdrive N8 and Megadrive Everdrives uses a Cyclone 2; the SNES Everdrive X5 seems to use something else, so possibly not possible there.

SD2SNES is 62-pin native, so you can't slap on an adapter to attach it to NES et al.

Offline SkinnyV

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Re: SNES/Megadrive adapter
« Reply #1 on: November 06, 2019, 07:33 PM »
Without going into technical details, this ain't possible for several reasons.

Offline bluefoxicy

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Re: SNES/Megadrive adapter
« Reply #2 on: November 07, 2019, 03:27 PM »
Can you specify what reasons? I can't imagine any, and it is possible to make a single card that can connect to any of the various cartridge systems slots if loaded with the correct firmware for the system.  Maybe the Everdrive N8 is designed in a manner that makes that not work, though.

Offline Sarge

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Re: SNES/Megadrive adapter
« Reply #3 on: November 08, 2019, 07:15 PM »
My guess is that it would be challenging from an electrical standpoint. Each system probably expects a certain setup on the pins for voltage/current. I'm not an expert, though; I'd need to dig into the documentation to see what is or isn't possible. I'm guessing folks over on the NESDev forums might have a better answer to a question like this.
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Offline bluefoxicy

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Re: SNES/Megadrive adapter
« Reply #4 on: November 09, 2019, 01:18 AM »
Yeah. Most systems are 5V, with the cartridge running 3.3V.

Many cartridges are using resistors or diodes to clamp voltages in a way that can damage your system.  The Everdrive N8 is pretty decent and the SD2SNES is well-engineered; some cheap 32-in-1 cartridges are using straight resistors.

With a resistor network, you suck power and dissipate some as heat, or shunt it to ground.  In such a design, current still flows.

If you want to, you can instead run a low-power MOSFET and a low-power timer, causing the voltage to pull up if it's below 3.3V (less resistance, draws more current, more load on your system and power supply) or pull down if it's above 3.3V (more resistance, draws less current, less load on the system).  A feedback circuit causes this to self-adjust:  if you put it in a 12V system, the duty cycle cuts back and it draws less current; put it in a 5V system and it draws more current.

That's an extra $8-$12 of parts, though.

Note that the address and data lines on the memory chips have to be matched in hardware anyway.  All of that can be varied, and the adapter cable/card can contain the necessary matching circuitry.  It just might cost an extra $5-$10 (rather than paying $200 for a complete set of $190 of circuitry).

Offline SkinnyV

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Re: SNES/Megadrive adapter
« Reply #5 on: November 10, 2019, 10:31 PM »
Can you specify what reasons? I can't imagine any, and it is possible to make a single card that can connect to any of the various cartridge systems slots if loaded with the correct firmware for the system.  Maybe the Everdrive N8 is designed in a manner that makes that not work, though.

I won’t waste time explaining since you « know » its possible. Instead, I will be waiting for your super universal flash cart.

Offline Sarge

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Re: SNES/Megadrive adapter
« Reply #6 on: November 11, 2019, 06:51 PM »
Hey, I don't think that tone is called for.

Anyway, even if it is possible (and it very well may be), I think the real barrier is coding effort, time, and money. Maybe there would be a lot of demand, but I have my doubts; aesthetically it would be a bit of a mess. KRIKzz certainly wouldn't want to do so since he has an entire line of carts he can sell individually.
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Offline Davestra

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Re: SNES/Megadrive adapter
« Reply #7 on: January 17, 2020, 12:11 AM »
Yeah, Sarge has a point. These things usually take time.