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Multi Joy on the 5200… is it possible?


Lynxpro
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So I'm now enamored by the "Multi Joy" devices on the Atari 8-bit computer side.

 

For those who are unfamiliar with these devices and haven't seen them before, check out this thread:

 

http://atariage.com/forums/topic/223879-atari-8-player-multijoy-adaptor-new-full-color-assembly-instructions/

 

Mind you, those more recent A8 titles supporting 8 players would have to be transported over to the A8. I initially thought the devices were automatically read by the XL/XE computers as if they were equipped with standard 4 joystick ports like the 400/800 but apparently there are patches to apply. Still, this could be a way to restore 4-player gaming abilities to 2-port 5200s [questionable whether a 4-port 5200 BIOS chip would still be needed].

 

http://atariage.com/forums/topic/245763-multijoy-for-sale/

 

Currently, there's apparently 43 A8 titles that support the Multi Joy:

 

http://a8.fandal.cz/search.php?search=multijoy&butt_details_x=x

 

Continuing, according to Mathy's comment, it appears that the Multi Joy actually can support 16 joysticks [does that mean 32 paddles on A8? I dunno]. I'm assuming that's with 2 Multi Joys plugged into both joystick ports. I'm trying to wrap my brain around 16 - or 32 - working 5200 joysticks connected to 1 5200. Or 16 Trak-Ball controllers for that matter.

 

Forget the hashtag for #mindblowin, to ponder the thought, it's this full-on:

 

http://ecx.images-amazon.com/images/I/61MBcUwrUfL.jpg

 

The 5200 would then be king of consoles - okay, tied then with an XEGS with such devices - in terms of bragging rights to the number of controllers it could use for multi-player if these devices could be adapted for the 5200. Even more so than the Sega Saturn with 10-player Bomberman.

 

There's apparently also a lot of 4-player development over in the C64 retro scene involving both hardware and software mods. I have to admit, [alternating] 4-player Marble Madness is cool [but they don't have Trak-Ball support on it, sukkas!]; same with 3-player 8-bit Rampage. They also have a cool 4-player Warlords clone called Space Lords…yes, I know "we" have Castle Crisis on our side as well as the real 5200 Warlords if the original Atari programmer would release it.

 

http://www.protovision-online.com/hardw/4_player.php?language=en

 

 

 

 

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Should be pretty easy. I'm not sure how the MultiJoy itself works but all you need is something like a counter/demultiplexer (or is it multiplexer? Can never remember which is which) to provide power to each joystick in turn. The software would cycle through each port, enabling each joystick momentarily as it goes (the joystick inputs on the A8 can be set to output, so presumably the 5200 can as well), read the input and then move to the next one.

 

That's all there is to it. No magic involved. :)

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Should be pretty easy. I'm not sure how the MultiJoy itself works but all you need is something like a counter/demultiplexer (or is it multiplexer? Can never remember which is which) to provide power to each joystick in turn. The software would cycle through each port, enabling each joystick momentarily as it goes (the joystick inputs on the A8 can be set to output, so presumably the 5200 can as well), read the input and then move to the next one.

 

That's all there is to it. No magic involved. :)

 

So I guess the next step would be to wire up one with DB15s and then get one of those 43 games transported over to the 5200 as a ROM and then test it with an AtariMax SD cart or an EPROM.

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Unfortunately the 5200 is missing the PIA chip which allows the A8 to use the joystick pins as outputs. I'd guess that's why the Multijoy uses 2 joystick ports. One port is configured as an output on the A8 to signal which joystick it wants to read. The other port is used to read that joystick's values.

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Unfortunately the 5200 is missing the PIA chip which allows the A8 to use the joystick pins as outputs. I'd guess that's why the Multijoy uses 2 joystick ports. One port is configured as an output on the A8 to signal which joystick it wants to read. The other port is used to read that joystick's values.

 

Sonofa! I didn't catch that from Maty's earlier comment post.

 

[Expletive]! That also means it wouldn't work for a 7800 either without a PIA chip installed via the XM.

 

And for it to work in a 5200, one would have to somehow design an upgrade to allow the installation of a PIA and also tweak the BIOS to accommodate it.

 

 

 

 

"The Atari can handle 16 players using 16 joysticks via a Multijoy Interface. PIA pins can be switched to output. When using a multijoy interface, one joystick port is switched to output, the other to input. "Input" reads the joystick, "output" selects which joystick is read. Sincerely Mathy"

Edited by Lynxpro
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Well, one way to do it would be to have an additional circuit that would send signals back to the keypad inputs telling the 5200 which joystick is being read. So instead of the software telling the multijoy which one to activate, the multijoy would rotate through the joystick ports and send the port's ID to the keypad inputs.

 

So yeah. It is still possible but you wouldn't be able to use the keypads for anything.

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Well, one way to do it would be to have an additional circuit that would send signals back to the keypad inputs telling the 5200 which joystick is being read. So instead of the software telling the multijoy which one to activate, the multijoy would rotate through the joystick ports and send the port's ID to the keypad inputs.

 

So yeah. It is still possible but you wouldn't be able to use the keypads for anything.

 

Wouldn't that then limit the number of controllers to potentially 12 based upon the keypad's number of keys?

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Wouldn't that then limit the number of controllers to potentially 12 based upon the keypad's number of keys?

 

Not necessarily. The 5200 was never released over here so I'm not 100% sure how they work but theoretically if you used a binary encoding system then you have potentially 128 controllers PER PORT as there are 7 pins (or maybe even 8 if you use Pin 4?) dedicated to the keypad. It would depend on how they're read and arranged in the relevant memory locations. If it only allowed 12 then that wouldn't be too bad as it would be 12 per port.

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