Joystick wiring solution to avoid installing additional buttons (A+B=C)

[Dreamcazman]

Hi all, I've only recently found this forum and I wish to share this mod as someone else may find it useful. Thank you for letting me join the group.

I have a Sega Astro City mini stick and as we all know there is only a Select (credit) button and a Start button. I wanted to mod it with a Brook UFB but also incorporate a Guide/PS Home button without having to install additional buttons.

An additional small circuit using a few common components can be made for this to work on all common ground boards. All credit goes to the gentleman here who helped me out with the circuit - https://electronics.stackexchange.c...uttons-to-trigger-third-input-using-common-gr

After confirming the circuit worked on a breadboard, I measured the voltage across the buttons on the UFB, which is around 3v-3.2v. From testing an Xbox controller too, this seems to be fairly common.

As the circuit is driven by the 5v from the USB connection, an additional two resistors are needed on the output to make basic divider circuit to drop the voltage from 5v to 3v. This may not have been necessary but I didn't want to take any chances. Anyways, I ended up using 3.3k and 5.6k resistors. A calculator can be found here - https://ohmslawcalculator.com/voltage-divider-calculator

Here is the end result of the complete circuit layout I designed on veroboard.

I haven't gotten it installed properly in the Astro City stick as I'm still waiting for a wiring loom but can confirm when you press both Start & Credit, it triggers Guide/PS Home. I will post pictures when completed.

I hope I explained this guide clearly and that it helps someone else out. Hit me up if you have any questions.

 

[buffi]

Couldnt you just use a OR-gate instead?

If I understand you correctly, the Brooks board has pullups on the buttons, so should be fine to just do

          VCC (3.3V)
          |
         _|__ 
B_A---->|    |
        | OR | ---> B_C
B_B --->|____|
          |
          GND

I might be missing something though

 

[Dreamcazman]

Couldnt you just use a OR-gate instead?

I don't think that would work as I want to press two buttons to then trigger the third 'virtual' button. I tried mucking around with an AND gate before this, but couldn't get it working, then again I was probably doing something wrong, lol. I know a little about electronics, but I'm no expert.

The buttons on the Brook (and other common ground PCBs) are normally high and are then pulled to ground when you press a button.

 

[buffi]

I don't think that would work as I want to press two buttons to then trigger the third 'virtual' button. I tried mucking around with an AND gate before this, but couldn't get it working, then again I was probably doing something wrong, lol. I know a little about electronics, but I'm no expert.

I mean, a AND gate will do the opposite of what you want, so of course that wont work

Since A and B are pulled up when not active, that should mean that C will be pulled up if any of them are _not_ pressed.
If both are pressed, the OR gate will send a low signal to C, making it active.

 

[Vinsanity]

Not sure if this would help others, but I was interested in something similar a while back. RiddledTV eventually put together a board for it: 2-3 button converter

Edit:
Here’s the conversation, and the initial drawing of the circuit: link

 

[Dreamcazman]

I finally got everything installed in my stick and tested it out last night, works perfectly.

The custom veroboard circuit is attached with hot glue, underneath the 3D mount I designed (sorry, forgot to take a photo of it).

Here is the link to the mounting plate STL file -> https://www.thingiverse.com/thing:5788797

Incidentally, I did have to install a 90 degree pin header as the harness would not fit, lol.

Overall, I'm very happy with how everything turned out.