3 and 6 button Megadrive pads

[Vertigo]

I want to do a stick to megadrive mod.

My supergun sticks are wired to NeoGeo standard for the first 4 buttons and then two extras for 6 button games so the basis of doing a custom stick mod comes from here.

I want to completely remove the chip from the controller so I end up with a smaller, neater package, instead of wiring to the pads/tracks inside the whole controller and having an 8 inch by 4 inch box.

I assume that this refers to the 3 button pad and that, going by what I gather from the chip and port pinouts, up and down on the d-pad bypass the controller chip and are wired directly to the input on the megadrive via pins 1 and 2.
This is fine, although I don't understand all the "2 inputs get you 1 output" explanation. Can you not just wire your stick buttons directly to the Left, Right, A, B and C pins on the chip?

With regard to the 6-button pad, how does this work? Is this what the "2 inputs..." bit refers to? How would I wire up the extra 3 buttons to this chip in order to have 6 button functionality? I've drawn myself a few diagrams and looked inside the pad I have but it's still resulting in confusion as it doesn't appear to be as simple as the wiring for a custom stick with 3-button capability.

Cheers.

[NFG]

Two inputs into the chip are fed to a single output based on the chip's SELECT line being HIGH or LOW.  HIGH, you get A.  LOW, you get B.  There are four of these 2->1 units on the chip, all controlled by the single select line.

The 6 button pad works COMPLETELY differently.  It's far more complicated, and would require about 10 chips to replicate.

Have you even looked inside a genesis pad?  Do you know how electricity works?  If you remove the chip how does it matter at all what it used to do?  It's only an issue if you want to keep using it.

Maybe I misunderstand your question, but if you're hooking this up to a supergun why do you have any chips at all?  JAMMA is chip-free.

[Vertigo]

No, you misunderstand, you're thinking about it the wrong way around.

I don't want to use my Megadrive pad on a super gun: "I want to do a stick to megadrive mod." i.e. use my arcade stick (which is wired to Neo standard with pins 2 and 10 connected for buttons 5 and 6 for use with super gun) on the Megadrive as dedicated Megadrive sticks are a) not great and B) more expensive than I have money for (yes, really!).

See, I take my Neo pin-out stick and attach the controller input port pin 13 to the Megadrive controller chip's pin 11 to get a functional A button (as long as the chip's powered and I have connected the stick's ground to the chip's ground).

Is the chip in the 6-button one different, having enough pins that I can again just wire straight to the chip, or is there all sorts of funny stuff going on in a 6 button pad that makes the technique different? Can I just trace the tracks from the buttons in a 6-button pad directly to a corresponding pin on the controller chip (like you would do to find out how to connect the 3-button pads) or is there some sort of extra jiggery-pokery going on in there that needs to be considered?

The reason I'm extracting the chip to use inside the adaptor is so that the Megadrive understands the button presses, see?

Another question about that 3-button chip. It has 4 ground pins. Do they all need to be connected, or can I get away with only connecting one to the ground loop?

[NFG]

Ah, see, now you're being clear.

The six button chip is, as I mentioned, completely different to the three button unit.  

Open your pad, see what components are in there.  Many of them have a resistor array to pull the inputs high, some don't.  You have to take whatever's in there and put it in your adaptor box.  

Connect all the grounds, it's easy, it's fun, and it's probably a good idea.

[Vertigo]

So the 6-button pad hs a different controller chip, but one that has more pins to take the extra 3 buttons (and mode button which I'll ignore as the DC stick has only 7 buttons) into account?

Oh, secondly, any idea if the chips in a 6-button pad are readily available components that I can buy a few units of for cheap, or would I be better off extracting them from a pad and adding resistors on the lines that need them?

[NFG]

I'm not sure what you're getting at with the first question.  Are you drunk?  Or maybe you're too sober?  You're <smack!> not <smack> making <smack> sense!!

any idea if the chips in a 6-button pad are readily available components that I can buy a few units of for cheap

What do you think I meant by "The 6 button pad works COMPLETELY differently. It's far more complicated, and would require about 10 chips to replicate."??

[Vertigo]

I'm not sure what you're getting at with the first question.  Are you drunk?  Or maybe you're too sober?  You're <smack!> not <smack> making <smack> sense!!

What do you think I meant by "The 6 button pad works COMPLETELY differently. It's far more complicated, and would require about 10 chips to replicate."??

The first questions means: "Can I wire buttons directly to the input pins on the 6-button pad's chip just the same as I can on most other pads?" Or is there some sort of unexpected silly stuff going on in the 6-button pad?

And the 2nd bit: I didn't know what you meant because your original post was in a response where you misunderstood what I was trying to achieve.

[NFG]

I've known you for so very long, and yet it's somehow escaped my notice that you have no idea what you're doing.  How did it get like this?  Oh, I remember - you stopped visiting us on IRC.  =P

Here's the short guide to removing the encoder from a pad so you can use it for your purposes:

1. Remove encoder and all supporting components from pad
2. connect new buttons to the components where the old buttons used to connect.

[Guest]

What, no step by step diagrams?

I was simply (!!!!) asking whether there was some funky shit going on inside a 6-button pad that was unexpected.

A simple "No" would have sufficed.

Check out my big wooden spoon, it's lovely, ain't it?

You never did give me a reaction to your birthday tanjoobi-kaado by the way.

[NFG]

I was simply (!!!!) asking whether there was some funky shit going on inside a 6-button pad that was unexpected.

Look first, ask later!  Don't make me come over there!!

Your card was lovely, thanks.  Not enough monkey love though.