8bitdo Retro Receiver + M30 Controller. Accessing A button?

[Aljrob]

Hi All,

So I was feeling pretty pleased with myself this evening having managed to knock up an adaptor to use the 8bitdo retro receiver + M30 bluetooth controller with my newly purchased A1200. (Switch the wiring to pins 5 and 7 for anyone wondering - Amiga pin 7 is +5v, megadrive +5v is pin 5).

Works well, and I’d thought it would be simple to attach a jump lead to shadow button A on the megadrive pad to “up” (pin 1) to give me a dedicated jump button. I know this is possible on a wired megadrive pad, but i’m stumped on this wireless receiver. I don’t have an oscilloscope to hand but via a normal multimeter I can’t see any signal being output on any of the 8bitdo retro receiver’s output pins when I press the “A” button. I guess it must be some sort of digital encoded signal.

I can see voltage change signals for up, down, left, right, B and C, but no other buttons.

Any pointers anyone can share?

[LIV2]

Megadrive controllers multiplex the A/B and C/Start buttons over the same pins depending on the state of the SELECT pin so it isn't possible to do what you want without some more complex circuitry

Here's a reference for the MD 3-button controller protocol https://www.raspberryfield.life/2019...bc-controller/

[Daedalus]

Swapping pins 5 and 7 allows the Amiga to read all 4 buttons, but the game needs to explicitly support this. If you are trying to modify the output from the receiver going into the Amiga, it's a little more complex because you need to take into account the different "banks" of inputs. Button A is on a different bank and so will never be active at the same time the Amiga is trying to read the up button. The state of the A button needs to be read invisibly from the Amiga and then applied to the up pin (pin 1). A couple of latches or a small microcontroller would do it easily, but that's getting quite involved.

You can probably still modify the controller itself so it transmits an "up" signal when A is pressed, but that of course will mean it won't work properly with an actual Megadrive (or any other system you use the controller with).

[alexrentier]

I would start with the controller and look further step by step what works and what doesn't! Element by element, and there you can already understand the reason!