Linking An Atari

Post by **SpongeBuell** » Fri Jan 21, 2005 8:03 pm

JackFrost22 wrote:Closing...

ummm...

JackFrost22 · Post by **JackFrost22** » Fri Jan 21, 2005 8:18 pm

So im not a superhero. So what happened when I covered myself in toxic waste
JackFrost22
Yes?
You have lyhpoma
Oh!
Probably from rolling around inthat toxic waste
Oh
What were you tryingt o prove?
Stupid yes idiotic yes
Closing...~

A.J. Franzman · Post by **A.J. Franzman** » Sat Jan 22, 2005 1:23 am

JackFrost22 wrote:Well i eveltually figuresd out howe to link them and I did it the wayh you were talking about so i dont care
Closing...

Jack, we're trying to set a standard here so whenever ANY of us with Vlink-capable portable VCSs meet up, we can enjoy some multiplayer action. If I'm only going to build a unit for myself, what's the point of making a Vlink if it isn't compatible? Do you even know if your unit(s) is compatible with any others?

WHICH way did you build yours anyway, with the switch to swap audio and video lines?

See, the point of having a standard is to not need a switch. Some of us don't want to add yet another switch, and some of us might not even have room for one. Since Ben seems to have been first (and probably has built the most) with link capability, it only makes sense to adopt his method as the standard, if he'll share it. If he won't, well maybe we can get it out of him by torture or other devious methods...

JackFrost22 · Post by **JackFrost22** » Sat Jan 22, 2005 7:18 am

\ o5 o4 o3 o2 o1/
\ o9 o8 o7 o6 /
\___________/

1 Up
2 Down
3 Left
4 Right
5 Video
6 Button
7 Audio (L)
8 Ground(-)
9 Audio (R)
Then a switch to make them iputs if its the second player or out puts for the first player

A.J. Franzman · Post by **A.J. Franzman** » Sat Jan 22, 2005 11:56 pm

So you decided to use pin 7, eh? Just hope nobody does anything weird like plug your link cable into a real VCS...

Why? Pin 7 is defined as +5V (for paddles and other assorted controllers - see http://users.erols.com/tiltonj/games/tech/2600cont.html). I wonder what your portable will do with +5V on the Audio L line.

Post by **SpongeBuell** » Sun Jan 23, 2005 12:04 am

he probably doesn't play paddle games much.

A.J. Franzman · Post by **A.J. Franzman** » Sun Jan 23, 2005 12:49 am

That's not the point.

The point is, from a design perspective, it's a bad idea to use a pin for a different purpose than the canonical designation, especially where power and ground are concerned. Just because a Vlink cable doesn't need to carry +5V power, doesn't mean we should go ahead and use the power wire for something else!

The question we're still trying to get answered, is should the video go on pin 5 or pin 9? Where did Ben put it? Does anyone on these boards own one of his Vlink-enabled portables?

(The other pin of those two would naturally be mono audio.)

On the other hand, it might be OK to use pin 7 as long as a safety measure is in place (such as an appropriately rated capacitor, preferrably non- or bi-polar, to pass the audio or video signal but block DC). In this case, I would put RIGHT audio on pin 7. That way, people with mono units using pins 5 and 9 would still be connected appropriately. The industry standard for mono/stereo compatibility has been to use the left channel for mono signals for many years.

Unidentified Assilant · Sun Jan 23, 2005 3:59 am

I want to do this on my handheld megadrive that I'm hopefully making soon so I can link 2 together and have multiplayer fun with other people, because megadrive has some really good 2-player games.

MM007 · Post by **MM007** » Sun Jan 23, 2005 12:02 pm

Unidentified Assilant wrote:I want to do this on my handheld megadrive that I'm hopefully making soon so I can link 2 together and have multiplayer fun with other people, because megadrive has some really good 2-player games.

Hmmm....

If we can't get Ben's standard, maybe we can at least set up something...I'm thinking a DB15 connector(GamePort/MAC Video/Old school NIC/Famicom EXT.) with these connections(not in order):

Up
Down
Left
Right
Button
Video
R Audio
L Audio
A/V GND
Paddle
Battery*
Battery GND*

Then you have 3 free wires.

*Battery and Battery GND effectively connect the battery systems of the two systems in parallel and power the two units simultaneously. This way, one system can NOT die out before the other. If one battery has died, both systems run off of the remaining battery system. However, to do this the systems must both be running off of the same voltage. The voltage must be standardized as well for this to work...

Post by **gannon** » Sun Jan 23, 2005 12:40 pm

also, I'd recommend a 5V line to power a relay in the slave unit so only the screen/controller recieves power.

MM007 · Post by **MM007** » Sun Jan 23, 2005 12:42 pm

gannon wrote:also, I'd recommend a 5V line to power a relay in the slave unit so only the screen/controller recieves power.

Good idea. Then battery life will be even longer. ^^

A.J. Franzman · Post by **A.J. Franzman** » Sun Jan 23, 2005 9:13 pm

True, turning off the VCS motherboard in the slave unit would save power, but we need to confirm that this is OK before going ahead with it.

I can think of 2 possible problems, mentioned back on p.1 of this topic:

1. Having an unpowered unit connected to a powered unit's controller port could screw up the controller signals - for example, by making all pins on the master unit appear to be grounded. This would be a Bad Thing.

2. Having power on the slave unit's controller port pins without power to the chips (Stella and RIOT) could fry the ICs.

Since joysticks work by grounding the pins, this seems at first to not be a problem. But, we need to realize that the controller port pins of TWO VCSs will be connected together via the link cable. The pullup resistors in the powered unit would be providing some voltage through the link cable to the unpowered ICs. If this kills the ICs in the unpowered unit, this would be a Really Bad Thing.

Post by **gannon** » Sun Jan 23, 2005 9:16 pm

then use the 5V to power an ic latch so there is no connection to the slave units ICs

A.J. Franzman · Post by **A.J. Franzman** » Sun Jan 23, 2005 9:24 pm

That would require a relay with at least 6 (preferrably 8-10) poles. Have any idea how big they are, or how much power they take? A solid-state relay (or CMOS bilateral switch) might be a workable option.

Post by **gannon** » Sun Jan 23, 2005 9:27 pm

That's why I said an IC latch and not a analog relay