Support two buttons on Sega DB9 controllers

[danboid]

The MiSTeryShield20K supports 2 fire buttons for DB9 joysticks so would it be possible to add support for Mega Drive controllers so that we can use 2 fire buttons on games that support 2 fire buttons?

Here's a list of C64 games that support more than one fire button:

https://wiki.icomp.de/wiki/DB9-Joystick#C64

Thanks

[danboid]

I no longer own a real C64 (sold mine over 30 years ago) but apparently you need to use an adapter to safely use a MD controller on a C64 such as:

https://github.com/SukkoPera/OpenC64MegaDrivePadAdapter

or the Mega Switcher:

https://www.youtube.com/watch?v=wY4szU_4eSE

My 6 button Mega Drive joystick works fine with the MiSTeryShield20K DB9 port but only the B fire button works with C64Nano.

[danboid]

It seems the best way to implement this, if possible, would be to have the Mega Drive's B button mapped to the MiSTeryShield20K BTN0 (as it already is) and the MD's C button mapped to BTN1.

This button mapping would allow for both Master System and Mega Drive controllers to be used for 2 button C64 games.

Master System Button Mega Drive Function

Button 1 B Button
Button 2 C Button

[danboid]

Looking through the commit history it seems C64nano might already have support for 2 button (Commodore?) controllers?

5479ca9

The existing second button support doesn't seem to work for Sega controllers.

[harbaum]

Mega drive controllers IMHO use a quite different approach and not just add a second button but add an output that switches between two different sets of inputs. The 6 button controllers are again very different.

It's possible to implement and use that on boards that have bi-directional level shifters and implement all required pins. I'd need to check if any of our boards support that.

Bit IMHO it doesn't make too much sense to add special support for all kinds of controllers.

My approach back with the MiST was to simply use USB adapters whenever I wanted to use some strange/uncommon controllers. This worked for mega drive controllers and also for c64 analogue paddles and the like. I think this is the way to go as it keeps the hardware and cores simpler for these rather rare use cases.

[danboid]

I'm not asking you to support all sorts of controllers, specifically and only Master System and Mega Drive controllers and only 2 buttons, not all 6/8.

The Mega Drive remains one of the most popular 16 bit platforms and has one of the most active homebrew scenes today, rivalled only by the Commodore scene. On top of this, we now have the increasingly popular Spectrum Next and its clones which use Mega Drive controllers which has led to more new MD compat joysticks being manufactured and sold online. They're a lot easier to buy than Quickshot joysticks and they're much nicer to use.

Clone, 6/8 button MD controllers can be bought from AliExpress for as little as $2 and people can build their own MD joysticks for less than $20.

https://github.com/danboid/genesis_6button

Thanks @harbaum

[danboid]

In answer to my own question earlier about existing 2 button support in C64Nano, I noticed it says this in the README:

Emulation of [C64GS Cheetah Annihilator](https://en.wikipedia.org/wiki/Commodore_64_Games_System) Joystick 2nd Trigger Button (Pot X/Y)

I can't imagine very many people own one of those joysticks. Sega sold at least 30 million Mega Drives according to wikipedia:

https://en.wikipedia.org/wiki/Sega_Genesis

So there must be at least 30 million MD controllers out there and that isn't counting 3rd party controllers or Master System controllers.

Wikipedia says Commodore only sold about 2000 C64GS systems:

https://en.wikipedia.org/wiki/Commodore_64_Games_System