SMS pad hacking

[joe-musashi]

I am working on an arcade panel for my beloved old SEGA Master System I (SMS). For now I am building a prototype out of a small table, just to have a place to fix the arcade joystick and buttons while I experiment with soldering and wiring.

I havde attached a picture of the PCB from an old control stick that I have taken apart. I plan to 'pad hack' this control stick, in the sense that I will connect the new arcade controls to this control stick PCB, and then use the original cable to connect to the master system power base.

I need your help on two issues:

1) Am I right if I claim (from top to bottom): Silver = ground, black = ground, white = button 2, blue = button 1?

2) Can I make a third button (acting as button 1 and 2 pressed simultaneously) by soldering an additional wire to both of the solder points of the white and blue wires (the other end of the wire soldered to the third button on the panel)? I know I also have to ground this third button. I think it would be cool to have a button for magic in Golden Axe...

[ApolloBoy]

It's fairly unnecessary to pad hack an SMS controller since it doesn't use any multiplexing; you can wire everything straight up to a DB9 cable and that's it.

[joe-musashi]

Thank you, that makes sense. Any thoughts on making a combined 1+2 button = button 3?

[ApolloBoy]

Thank you, that makes sense. Any thoughts on making a combined 1+2 button = button 3?
Wire the lines for both button 1 and 2 to the button contact and then add your ground as you would for the other buttons.

[joe-musashi]

OK. Thank you for your advice! Just to be sure I understand you correctly: I wire buttons 1 + 2 like normal, and then I solder two wires to button 3; one wire goes to the button 1 contact and the other goes to button 2. Then grounding...?

[ApolloBoy]

OK. Thank you for your advice! Just to be sure I understand you correctly: I wire buttons 1 + 2 like normal, and then I solder two wires to button 3; one wire goes to the button 1 contact and the other goes to button 2. Then grounding...?

That's right. You want to make sure all your buttons and the joystick are grounded otherwise they won't work.

[bust3dstr8]

You can't just split both wires and then connect to button 3.
That would short the two for button 1 and 2 also, giving you a double button push for all the buttons.

You would need to isolate the inputs with two AND logic gates.
Depending on how the inputs behave you may have to add pull-up resistors to the inputs as well.

[ApolloBoy]

You can't just split both wires and then connect to button 3.
That would short the two for button 1 and 2 also, giving you a double button push for all the buttons.

You would need to isolate the inputs with two AND logic gates.
Depending on how the inputs behave you may have to add pull-up resistors to the inputs as well.
Ah that's right, didn't think about that at first.