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VCS Joysticks on Genesis


gliptitude
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Many of us know that a Sega Genesis controller will work on a 2600.

 

This recently caused me to think and hope that a 2600 joystick could also work on Genesis.

 

My roundabout experiment at doing this suggests that the Atari controllers do NOT work properly on a Genesis and I am wondering why this is the case and if there might be something simple I could do to make it work, (such as a simple pass through device that was only changing a pinout or two).

 

.. Obviously Atari controllers do not have enough buttons to fully satisfy the Genesis but I was expecting that the Atari button would still correspond with ONE button on the Genesis, which would be enough to play some games, (like Sonic I think), and that the stick would correspond directly to the Genesis D-pad.

 

.. My real goal was to play on a Vectrex using the Genesis to Vectrex adaptor that I have. This is how I tested "2600 to Genesis compatibility", rather than on an actual Genesis, (because I don't have one). The adaptor works fine for using Genesis controllers on Vectrex, but it has several problems when I plug the 2600 joystick into the adaptor, (monitored with Vectrex test cart):

 

- When the joystick is physically centered the Gen adaptor/Vectrex indicates that the joystick is constantly pointed DOWN and LEFT.

 

- Moving the joystick in any direction does cause the corresponding correct direction, but releasing the joystick immediately results in down/left again.

 

- Pressing the fire button signals two buttons simultaneously, (Genesis B and C I think), (probably not a problem for my purposes but perhaps an indication of what is happening).

 

Anybody have a thought on this? It probably seems like a silly endeavor, but I have a pretty rare and unique VCS joystick that I really like using and I'm always looking for fun new things to do with the Vectrex. Fortress of Narzod would be sweet with this joystick.

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Looking quickly at a Genesis controller schematic, it looks like the outputs are all pulled up to 5 volts when inactive (not pressed) and pulled down to 0v when activated. The 2600 controller doesn't have those pullup resistors. The adapter may just not like the 2600 controller inputs floating when they're not active (pulled to 0v). Instead of toggling between 5v and 0v like the Genesis controller, the 2600 controller outputs toggle between nothing (high impedance) and 0v.

 

This is the schematic I referenced, in case it is in error:

http://gamesx.com/wiki/lib/exe/fetch.php?media=controls:genesis_pad_schematic.png

 

Taking a semi-educated guess, I'd expect the adapter with no controller plugged in to exhibit the same behavior as when a 2600 controller is plugged in and left in its neutral state.

 

If that proves to be the problem, and you really, really want to play the Vectrex with a 2600 controller, to fix it, you can tie pin 5 of the adaptor to each of the joystick directions and fire button pins through an appropriately sized resistor. 10K ohms would probably be safe.

 

It shouldn't be too difficult to build an adapter to play vectrex with a 2600 controller more directly. It could be done with all passive components.

 

Not sure how many Vectrex games you'll be able to play effectively with only one button no matter which way you go about hooking up the controller.

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An Atari 2600 controller does work on a Sega Genesis with the fire button as the B button. This is because the Genesis controller is backwards compatible with the Master System controller.The Master System uses the same pinout as the 2600, so Master system controllers work on the 2600. (The only thing is the Master system has a second button which does nothing on a 2600).

 

A Genesis Vectrex adapter will only work with a Genesis controller on a Vectrex. Just because A works with B, and B works with C, does not mean that A works with C.

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Thanks for the replay BigO.

 

Taking a semi-educated guess, I'd expect the adapter with no controller plugged in to exhibit the same behavior as when a 2600 controller is plugged in and left in its neutral state.

 

If that proves to be the problem, and you really, really want to play the Vectrex with a 2600 controller, to fix it, you can tie pin 5 of the adaptor to each of the joystick directions and fire button pins through an appropriately sized resistor. 10K ohms would probably be safe.

 

It shouldn't be too difficult to build an adapter to play vectrex with a 2600 controller more directly. It could be done with all passive components.

 

Not sure how many Vectrex games you'll be able to play effectively with only one button no matter which way you go about hooking up the controller.

You are correct that the adapter with no controller gives the same indication as it does with neutral 2600 controller.

 

There are several great Vectrex games that only require one button (Vectrex button 4) for in-game play: Fortress of Narzod, 3D Narrow Escape, Starhawk and Vector Pilot. There are a few more games that are not so great.

 

I don't quite understand the theory and all the variables you lay out, but it sounds like the pin-5 tie in through a resistor could be done easily with an additional in-between adapter. .. But if a new dedicated device could be just as easily devised I guess that would be even better. It would be nice to have a switch to change which Vectrex button the 2600 button corresponds to, or maybe even have buttons on the device for Vectrex buttons 1, 2 and 3, (for menu navigation..).

 

As I recall the Vectrex controller is more complicated than the Atari one, with a few resistors. Also analog joystick.

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I've made "digital" Vectrex controllers from scratch and analog controllers would be easy, too. Yes, it's a bit more complicated than a 2600 controller, but it's still all passive components, meaning no chips or transistors or anything like that. Just switches and resistors.

 

You could make a device that plugs in between your 2600 controller and the Genesis->Vectrex controller to do the pullup. You'd need 5 resistors, a male DB-9, a female DB-9. If you can solder, you can build it.

 

I assume the Gen->Vec adapter must handle the mapping of Genesis buttons to Vectrex buttons. To map the 2600 button to various Genesis buttons on the controller side of the adapter might be a bit tricky. I'd have to do some studying of the Genesis controller to determine if that's feasible without any additional electronics. It's been too long since I tinkered with one to remember the nitty gritty details.

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Here's the schematic for my homebrew vectrex controller:

http://atariage.com/forums/topic/117809-homebrew-controllers-modernish-5200-and-vectrex-digital/?p=1560121

 

Now that I look at this again, I can see that it wouldn't be quite so easy to build an adapter directly between the Vectrex and a 2600 controller. The roadblock is that the directional controls on the 2600 all share a common point. That won't work directly to control a Vectrex. Again, too much time has passed.

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I remember trying to play Sonic the Hedgehog with an atari joystick and it worked. Though the only reason why I tried that was because the genesis controller that came with my genesis had dirty contacts.

 

I did this once too... Of course I had to start the game with the Sega controler (Press Start), unplug it and plug in the Atari stick.

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