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Gear To Gear cable and pinout
Post Posted: Sat Aug 07, 2010 3:00 pm
Hello
I am looking for the pinout of the gear to gear cable and the connector it self.
After looking at this: http://www.smspower.org/Development/GearToGearPortSMSControllerAdaptor I figured that it would be posible to conect two SMS:s or one game gear and one SMS.

And since I guess that a gear to gear cable is quite rare could I replace it with a de-9 without loosing any signals?
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Post Posted: Sat Aug 07, 2010 8:42 pm
The pinout you linked is for an adaptor to allow plugging in a P2 controller in SMS mode in GG games. It does not allow linking an SMS to a GG. The Gear-to-Gear pinout requires someone to test a cable, which nobody has done yet :(

You could connect the consoles with some custom code and some kind of serial protocol, but I guess that is not your intention?
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Post Posted: Sat Aug 07, 2010 9:49 pm
Is there any docs that I could read on how to use the EXT. port of the GG? If I am guessing right it is "just" a controller port that they converted to a EXT. port and that it needs a software driver to work.
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Post Posted: Sat Aug 07, 2010 10:23 pm
I thought the workings of the G2G cable had been gleaned from game code?

Certainly we seem to have basic documentation in the dev section on how to drive it, and I believe its emulated to an extent on some emulators.
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Post Posted: Sat Aug 07, 2010 11:04 pm
Skräp också!
Well, my grand plan didn't work out but now I have two new ones, laplink clone using only 2bit at the time. the second one and probably the better one is to add a zilog sio chip to the cartridge. but that is no fun and not cheap but I get two serial ports instead. hm...
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Post Posted: Sun Aug 08, 2010 3:34 pm
Maxim wrote
The Gear-to-Gear pinout requires someone to test a cable, which nobody has done yet :(
What can this Italian man do for you?


Maxim wrote
You could connect the consoles with some custom code and some kind of serial protocol, but I guess that is not your intention?
As far as I know, there is at least one Genesis game which did that: Zero Tolerance. So console-to-console is definitely possible.
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Post Posted: Sun Aug 08, 2010 8:27 pm
Please help me Italian macho man!
Also please use this numbering scheme, less the confusion the better.
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Post Posted: Sun Aug 08, 2010 8:44 pm
I *want* to help, I just need to know what I should do :P
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Post Posted: Sun Aug 08, 2010 9:09 pm
Find some way to measure continuity (e.g. an AA and an LED) and figure out which pin connects to which at each end.
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Post Posted: Sun Aug 08, 2010 9:14 pm
oh, you would need to continuity test the cable using a multimeter or something of the sort.
then you would need to test what 1 to 10 in one end comes out in the other end. one contact in one end might come out as two in the other. (this is the case with fully wired null-modem cables for computer to computer use.) also test if there is any loop back connections as well aka. goes in and comes out in the same end.
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Post Posted: Sun Aug 08, 2010 11:13 pm
Last edited by Tom on Mon Aug 09, 2010 1:56 pm; edited 1 time in total
EDIT: THIS POST CONTAINS WRONG INFORMATION. THE CORRECT PINOUT IS HERE.

I ran extensive tests.
First, the cable actually has 8 pins, and not 9 or 10.
There are no loopbacks.
There are, however, two pins that don't go anywhere.
As for the other ones:

1 -> 3
2 -> 4
3 -> 1
4 -> 2
5 -> nowhere
6 -> 6
7 -> 7
8 -> nowhere

The external shields are connected as well.
56568175.png (278 B)
Attachment fairy
56568175.png

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Post Posted: Mon Aug 09, 2010 8:13 am
GhstWlf wrote
Is there any docs that I could read on how to use the EXT. port of the GG? If I am guessing right it is "just" a controller port that they converted to a EXT. port and that it needs a software driver to work.

There aren't any great docs - I think the best is this:

http://www.smspower.org/uploads/Development/jon.txt

The controller port mode is really only in SMS mode on the GG. It has decent hardware support for the "proper" Gear-to-Gear connection mode; the 7-bit bidirectional mode is not used by anything except the Squinky Tennis minigame.

Tom wrote
First, the cable actually has 8 pins, and not 9 or 10.

Are the pins offset in the cable? (I can't tell from your photo.) Are there 10 pins in the GG-side connector? Is your picture based on looking into the cable or into the GG?

I made a preliminary page here:

http://www.smspower.org/Development/GearToGearCable
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Post Posted: Mon Aug 09, 2010 10:06 am
http://tfla-01.berlios.de/ <-- simple logic analyser, now the only thing is to get code on to the game gear that I can control or just dump the Columns data (got two of that)

windows binaries exists too: http://developer.berlios.de/project/showfiles.php?group_id=3948
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Post Posted: Mon Aug 09, 2010 10:46 am
Incidently I also have a G2G cable, plus one of these & scope, what I lack is the ability to run custom code.
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Post Posted: Mon Aug 09, 2010 12:21 pm
Maxim wrote
Are the pins offset in the cable? (I can't tell from your photo.) Are there 10 pins in the GG-side connector? Is your picture based on looking into the cable or into the GG?




Here you are the uncropped pictures in case you want to re-crop them by yourself for consistency or something:
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Post Posted: Mon Aug 09, 2010 12:59 pm
Great, I updated the wiki page to be consistent with the other doc (basically, including the missing pins).

The software side suggests there's more pins connected than the 6 you found (well, I think it could manage with 7). Is your cable an "official" one?
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Post Posted: Mon Aug 09, 2010 1:06 pm
Yes, my cable is an official Sega cable, and I successfully used it at least once as far as I can remember. I can test the pins again but I am pretty sure I got them right. I see the software seems to do it differently, I don't know why. It also seems that the software wants to cross the two central pins of the bottom row (5 and 6 in my pic), while they weren't crossed in my tests. Really weird.
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Post Posted: Mon Aug 09, 2010 1:16 pm
Well, it could be crossed in hardware somehow when using this "raw" mode. I'd expect there to be two pins used for common +5V and GND (?) which would have to not be crossed, plus however many pins are needed for the data transmitting and/or handshaking; there may not just be one pin state for a given "raw" parallel mode.
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Post Posted: Mon Aug 09, 2010 1:36 pm
I double checked, and I am very sorry to say I made a mistake the previous time. Pins 5 and 8 in my diagram are connected.



1 -> 3
2 -> 4
3 -> 1
4 -> 2
5 -> 8
6 -> 6
7 -> 7
8 -> 5

This time I'm 200% sure, as I checked it at least three times, back and forth.

Maxim, for the ground, keep in mind that the external shields are connected as well, and it's not unusual for the shields to be used as common ground. Though this is speculation at its best.

edit: I just noticed the page on the wiki. The pinouts you added in white over my photos aren't consistent with eachother. In those pics, it seems that pin 1 on the cable connects to pin 5 on the game gear, and so on. The wrong one is the numbering of the ext port, as the cable is consistent with the diagram on the left.
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Post Posted: Mon Aug 09, 2010 2:47 pm
Tom wrote
The pinouts you added in white over my photos aren't consistent with eachother.

You're right :( I'll fix it.
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Post Posted: Mon Aug 09, 2010 3:22 pm
Right, it is fixed now, but you crossed pins 7 and 8 in your diagram again :)

By using your numbering system, it should go like this:
1->3
2->4
3->1
4->2
X
6->9
7->7
8->8
9->6
X
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Post Posted: Mon Aug 09, 2010 4:24 pm
Aaargh :) Fixed.
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Post Posted: Tue Aug 10, 2010 9:48 am
Maybe if I get time I'll run the logic analyser across the pins with columns running in link mode and see if I can glean some useful info.
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Post Posted: Tue Aug 10, 2010 10:49 am
Well, you'll want to snoop on communications between two systems, else you won't see anything. On an emulator level it ought to be simpler as it can work on a higher level than the wire format.
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Post Posted: Wed Aug 11, 2010 9:39 am
of course, i've got multiple game gears and more than one columns cart that was the idea.

the problem with the emulator route is it assumes a lot about the hardware, and thats still a grey area in some cases.
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Post Posted: Wed Aug 11, 2010 11:49 am
This is jawusum ^^ :D
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Post Posted: Wed Aug 11, 2010 12:39 pm
djbass wrote
of course, i've got multiple game gears and more than one columns cart that was the idea.

the problem with the emulator route is it assumes a lot about the hardware, and thats still a grey area in some cases.


There isn't really much more to know about the gear to gear. Maybe some exact timing information would be good though, max speeds, etc, but it doesn't seem to matter too much (the games seem to have quite a bit of leeway in how they use the link, in fact some games don't work if you have two gamegears in cycle lock step, they basically loop around doing send/recv communication and expect the other gamegear to be at a different place than it).

RetroCopy has supported the gear-to-gear link since v0.720 and I have had every gear-gear game working at one stage or another. There is a bug in v0.720 though that stops a few of those games from working, something caused by some changes to my cycle accurate Z80 core I believe (haven't had time to verify yet but likely NMI related), but a lot of them work ok in the last release.

http://www.youtube.com/watch?v=GtqbQoz-WjI
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Post Posted: Wed Aug 11, 2010 1:35 pm
This is interesting to me because I want to make hardware that can use the Game Gear as a display, make a GG to SMS connection (if it works) and because nobody have done it before.
 
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Post Posted: Sun Apr 05, 2015 2:53 am
I would love to see more work done on this. I'm specifically curious if the Light Phaser can be supported through the Game Gear EXT port. Does anyone know more about what it does?

Of course you need a GGTV to use the phaser.
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Post Posted: Fri May 15, 2015 9:56 am
segasonicfan wrote
I would love to see more work done on this. I'm specifically curious if the Light Phaser can be supported through the Game Gear EXT port. Does anyone know more about what it does?

Of course you need a GGTV to use the phaser.


The problem with the phaser is it relies on the electron beam and scan line which only exists on CRT displays, making it non functional for modern LCD displays.

I've often thought of whether it would be possible to make an inline adapter to the LCD that flashes a bright dot at a coordinate relative to an emulated scanline position.

Or alternatively make a new phaser design that uses a cheap CMOS sensor to pickup a dot pattern or grid flashed on the display in a simular manor that is then encoded into a relative position back to the SMS.
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Post Posted: Sat May 16, 2015 7:46 am
That's not really a problem in my book. I never game on LCDs, and CRTs are dirt cheap everywhere these days.

Actually this is an old post, it was confirmed recently (in theory, not yet tested by me but will be soon) that the EXT port DOES have light phaser capability, but only for second player.

EDIT: I confirmed the EXT port works with the light phaser. However, the Gear Master cable lacks +5v (pin 5) so you must build your own plug :/
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