| Posted By
SukkoPera
on 2022-11-06
16:32:43
|  New 8-Player Joystick Adapter
Here's another project I've been working on, an 8-player joystick adapter for the User Port.
The original intent was to figure out how Solder's 3-joystick Adapter worked. It was pretty easy once I realized that the User Port has an output latch, but that also meant that even these 3 extra ports would suffer from the "bouncing ground" effect which prevents using powered controllers.
So I began thinking how to replicate the adapter while avoiding that and suddenly I realized that a very simple solution could be used and that it could easily be extended to support 8 joystick while retaining compatibility with the original adapter: I just used 5 8-to-1 multiplexers, one per direction plus the fire button. The multiplexer channel is chosen with the 3 high bits of the User Port, which means that the values required with Solder adapter will select ports 7, 6 and 4 respectively, just think about it (and yes, the silkscreen has wrong numbering, sigh).
The adapter can be connected to the computer through a cable with a User Port connector on one side and a male DB-15 on the other (which unfortunately I have run out of, so I could not complete it, grrrr!). I did this so that the adapter can be placed more freely on the table so that all players can reach it comfortably. The adapter-end of the cable can also be soldered directly to it, if you prefer (which is what I did for testing).
I know this might seem pointless but when I figured out the shape it would have, I couldn't stop  . And even less when I got the name! Of course there isn't much software support for this at the moment, but I tested it with Tron 6 and it works fine in "Solder compatible mode". To test the whole 8 ports I wrote a simple BASIC program and everything seems to work as it should. Now it's up to the developers to write party games for the C16/+4 for up to 10 players!
Well, not much more to say about that. Oh yes, the multiplexers I used (CD4051) are analog, so the adapter is bidirectional and the ports can also be independently used as 5-bit output ports.
This will be live soon, just need to prepare some docs. As usual it will be released as an open project under CC-BY-NC-SA so that everyone can build it on their own very cheaply: I estimate all the components required to self-build this thing to cost < 10€, probably closer to 5€ if you get them from China.
EDIT: Project is now live!
Again, I'm offering free boards to all forum members (you pay shipping), just ask, in particular if you plan to make a game supporting it!
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Posted By
siz
on 2022-11-07
03:14:28
| Re: New 8-Player Joystick Adapter
I was "working" (more like thinking) on a similar adapter but with four joystick ports supporting 2 fire buttons. (bit 0-4: directions, bit 5: fire1, bit6: fire2, bit 6-7: select port)
IMHO the second fire button would be more useful than having 8 joystick ports.
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Posted By
SukkoPera
on 2022-11-07
03:45:42
| Re: New 8-Player Joystick Adapter
Well, to be honest I tend to agree  . I had compatibility with Solder's adapter in mind, so that wasn't an option for me, but of course this design could be modified very easily to achieve that.
Another possibility with the current adapter would be to use one of the 5 bits currently available as an output and have it drive a multiplexer inside the controller, more or less like Sega MegaDrive/Genesis controllers work. This would be simple and allow for up to 4 buttons but obviously it would require ad-hoc-designed controllers (or more adapters, lol).
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Posted By
MIK
on 2022-11-07
07:05:58
 | Re: New 8-Player Joystick Adapter
The one game that comes to mind for 8 players... Bomberman!
Do I have 8 friends local to me? No. I can't even get my woman and two kids to play 4 player Gauntlet as they all have their own interests lol.
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Posted By
Csabo
on 2022-11-07
17:27:53
| Re: New 8-Player Joystick Adapter
As MIK said, this would probably get very little use other than retro parties. It's nice that it exists though, and the name is really clever!
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Posted By
SukkoPera
on 2022-11-08
03:46:57
| Re: New 8-Player Joystick Adapter
Yes, that was sort of expected, but the look and name it was going to have were so cool I just couldn't resist finishing it! It was also a nice design and routing challenge: How do I draw a Nonagon in Kicad? How do I route tracks with those weird angles?
So well, even if it gets no practical use, it was fun! But yes, a Bomberman clone for 10 players on the C16/+4 would just be supercool .
PS: Do we already have any Bomberman at all on the +4?
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Posted By
MIK
on 2022-11-08
07:00:54
| Re: New 8-Player Joystick Adapter
Bomberman type game, Xplode Man
PS. Sega Saturn Bomberman also supports 10 players.
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Posted By
SukkoPera
on 2022-12-03
18:23:35
| Re: New 8-Player Joystick Adapter
Well @siz, you asked for it, you got it .
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Posted By
Csabo
on 2022-12-04
17:04:34
| Re: New 8-Player Joystick Adapter
This 4-port version also looks great (and TBH probably would get more actual usage than the 8 player one). Does it have the 2 fire-button feature that siz mentioned?
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Posted By
SukkoPera
on 2022-12-04
17:29:32
| Re: New 8-Player Joystick Adapter
Yes, it should. I'm gonna order the prototypes and test soon.
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Posted By
MIK
on 2022-12-05
05:20:50
| Re: New 8-Player Joystick Adapter
It looks very tidy and cool but your missing the obvious..., It's a Plus 4! 
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Posted By
SukkoPera
on 2023-01-17
16:39:22
| Re: New 8-Player Joystick Adapter
Well, the first "thing" I made when I began replicating Solder's 3-way adapter was named "+4+3J" .
UPDATE 09/01/2023:
Happy new year everybody! I received the PCBs for this and some other projects right before Christmas, but I decided to stay in "off" mode until yesterday, when I finally began building and testing things. I am happy to report that the 4-player adapter works perfectly and allows reading two buttons. Button 2 is expected to be wired on pin 9 and to be active-low as all the other buttons. This is the most common configuration, used by Sega stuff (you can use Master System and Mega Drive/Genesis - buttons B and C - controllers straight away as the adapter also provides power to pin 5) and by all 2-button joysticks and adapters designed for the Amiga, including my PSX adapter and the BluePad32/Unijoysticle2. The few 2-button games for the C64 typically use inverted logic for button 2 (don't ask me why but this dates back to the C64 GS, I think), even if this was handled in SW, I cannot guarantee that any joysticks made this way will work correctly with the adapter.
I will release it publicly as soon as I have time, but if anyone would like a PCB, just ask (note that the 4x0603 resistor networks are a bit finicky to solder). I have already sent boards to @siz and @TLC, hopefully they can have some fun with them :).
UPDATE 17/01:
The project is now live and the board has been released, enjoy!
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Posted By
Csabo
on 2023-01-17
20:27:31
| Re: New 8-Player Joystick Adapter
Looks great, it's lovely to see it come to actual existence. I heard from siz that he did receive it. Awesome work
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