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Eyvind Bernhardsen

DIY Sega Mega Drive (Genesis) adapter

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There are screw holes for the D-sub connectors as long as you get connectors without board locks, my vague plan was to use them. As I said above, though, I haven't given much thought to the case yet; suggestions are welcome 🙂

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On 3/17/2021 at 5:52 AM, Bobo Cujo said:

I don't think it's a bad idea to have the ICSP header - imagine flashing different versions of the firmware if someone wants a different button layout...

Good point. I've uploaded a new version of my PR with three different PCB variants: the original ICSP version, the smaller version from my previous update, and a minified one with solder cup edge connectors like @manterola's (that one was tricky to design). Still waiting to receive my first lot from OSH Park.

 

Here's the new PCB:

 

1454836864_Screenshot2021-03-21at15_50_40.png.552c2acbfb4e24fd6dea58afb48bb8e5.png

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The postal service finally delivered my PCBs! Now to learn 3D printing so I have something better than electrical tape to wrap the adapter in.

 

IMG_0101.thumb.jpeg.de40deae5ca5948d6233c6ea4cee5f9f.jpeg

 

I made one with header pins for programming, but skipped them on this one. The DE9 connector felt a bit wobbly so I secured it with a couple of machine screws.

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Here's the BOM, with part numbers from Digikey. In addition you'll need the female end of a fully-connected joystick cable for the pigtail. 

 

The pin headers are optional, needed only if you want to enable C64 mode and/or program the PIC in-circuit. The nine-pin header easily snaps apart, just make sure you end up with a three-pin and a six-pin header.

Sega adapter BOM.csv

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Hello Eyvind

 

5 hours ago, Eyvind Bernhardsen said:

In addition you'll need the female end of a fully-connected joystick cable for the pigtail.

 

Would a joystick extension cord work if a (female?) DB9 connector was soldered in?

 

Sincerely

 

Mathy

 

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1 hour ago, Mathy said:

Would a joystick extension cord work if a (female?) DB9 connector was soldered in?

As long as the extension cord is fully connected I see no reason why it shouldn't.

 

Here's the closest female correspondent to the male connector I could find that's in stock at Digikey: https://www.digikey.no/product-detail/no/te-connectivity-amp-connectors/5745131-1/A33980-ND/1123756. Others may work, the important thing is that it's a .318" mount.

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I was working in a PCB version with both options: the edged D-Sub 9 connector or soldered pigtail + holes for plastic tie (for strain relief).

It is not ready yet. And I am not sure it really adds to what you have done.

image.png.1a2d8e12272efb11284a240453ba93b7.png

Edited by manterola
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48 minutes ago, manterola said:

I was working in a PCB version with both options: the edged D-Sub 9 connector or soldered pigtail + holes for plastic tie (for strain relief).

It is not ready yet. And I am not sure it really adds to what you have done.

image.png.1a2d8e12272efb11284a240453ba93b7.png


That’s interesting! How did you come up with the idea for the strain relief slots?

 

I think the capacitor could be moved under the PIC (which would need to be socketed) and the pins for the pigtail could be squeezed closer together, if you wanted to make it even more compact.

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This project has been on hold after long, possibly COVID related, shipping delays on pretty much everything I've ordered in the past year, but the last bits finally arrived and I'm ready to announce the next generation SEGA Megadrive controller adapter:

 

IMG_0199.thumb.jpeg.db7e0e5d5e63e920bed4fa0dfe5eb2e0.jpeg

 

The big changes are that it's smaller, and instead of a D-sub connector or a soldered-in pigtail it uses a detachable ribbon cable to connect to the computer. There's still a jumper to switch to C64 mode, for people so inclined.

 

Boards can be ordered from OSH Park, and there is a BOM with DigiKey part numbers in the GitHub project. Unfortunately the microcontroller seems to be out of stock at the moment.

 

This is still a DIY project, so you'll have to order parts, assemble them, and program the microcontroller yourself. It's open hardware: the source code is MIT licensed and the schematics are CC-BY-4.0.

 

I don't think I can make the board any smaller without switching to surface mount parts so the next step will be to make a 3D-printed case. Please don't hold your breath.

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Minor breakthrough: I figured out that the reason I couldn't read the X, Y, Z, and MODE buttons was timing related, and managed to fix the problem.

 

I have some ideas for using the extra buttons. In the meantime here's a preliminary build where X, Y, and Z simply shadow the A, B, and C buttons.

 

segaprog.atr

 

Note that I still only have 8bitdo adapters to test with (an order of Sega controller knockoffs from China was one of the deliveries that never arrived), and since this was a timing problem, different controllers might not work. Please report back if it doesn't work for you.

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My mouser order has arrived. I’m still waiting for Oshpark. 
 

I have some really crap genesis knockoff controllers here. @Eyvind Bernhardsen pm me your address I’ll send you one to play with. 

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Here's a build that has autofire for A, B, and C on X, Y, and Z, the simplest use I could think of.

 

segaprog.atr

 

The fire rate is around 12 Hz. I don't think it's possible to go above 12.5 Hz for buttons 2 and 3 (on PAL systems, 15 on NTSC) because charging the pot capacitors takes time and they are only drained once every frame, so the adapter needs to hold the button state for at least two frames to make sure the computer will notice. Could do a faster rate for button 1 or use the buttons for something else entirely, and the MODE button can be used to switch modes if necessary. Ideas welcome! :) 

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