GBA2GC MOD
As children my brother and I owned a GC, each with our own GBA SP and GBA to GC link cable.
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We played hours of the handful of games that utilized the link cable, or at least until one of our GBA SP LEDs would go from red to dead.
The original GBA to GC link cable covers the charging port on the GBA SP, meaning we would have to stop playing, unplug from the console, and go outside while we waited for a full battery.
This has bothered me for a long time, for no reason other than I would have had more time to play these games with my brother as a kid.
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In Dec 2023, I built my brother an SP slate using the same childhood GBA SP he used to play hours of FF:CC with me, not realizing that this would make the GBA to GC link cable incompatible.
The device is so thin that the original cable won't fit anymore, as it removes the hinge from the device.
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This bothered me. Again I find myself bothered by the design of this cable.
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The link cable was a way that me and my brother bonded over video games. I inadvertantly removed that functionality.
I invited him over to play some FF:CC for my birthday in 2024, and he had to use his modded GBA since the SP Slate would not work with the GBA to GC link cable.
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It didn't seem to bother him as much as me :)
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Regardless, this pushed me to try to solve both problems, which I think I have!
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PARTS:
RocketFish GC wireless controller receiver
Custom LED board
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TOOLS:
Heat Gun
Digital Caliper
Hobby Knife
Sand Paper
Airbrush
Paint
Metal file
This was the photo when i finally got everything working :)
BUILD INFO
Here are instructions on my version SP Slate compatible GBA to GC Link Cable!
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This can be built with all 3rd party off the shelf parts. I added extra to my build, but all that is required are the following:
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1 third party GC Controller Wireless Receiver with access to all 5 PINs on the GC controller port.
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I had a spare RocketFish GC Wireless controller that I did not like, so I used the receiver.
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I have opened up 4 or 5 different style wireless adapters. some do not have access to all 5 pins and only utilize 3. You could try to wire it yourself.
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I will try to update with a readily available device I've found that works for this mod, but at this time I do not have a link to a guaranteed working available 3rd party unit.
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1 GBA to GC link cable
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All that is needed are the internals of the adapter.
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1 GBC to GBC link cable
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You need access to 4 PINs in a certain order, and the GBA link cable PIN placement is not correct for this mod. A GBC to GBC link cable is required for this mod.
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You need access to at minimum pins 3, 5 and 6 for the GBA to GC link cable to work. Pins 1 and 2 are used for 5V and 5V ground, which seems to be enough to keep the SP from dying and charge the battery if you want to add USBC charging. (I am still testing this and working to add to V2.)
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From the GC Wireless Receiver, desolder any internal components to make room for the GBA to GC Link Cable internals. Make sure there are 5 cables coming from the controller port. A few I opened only had access to 3 pins.
Solder PIN 3 to the DATA pad on the GBA to GC link cable, PIN 6 to the 3v pad (maybe labeled VCC) on the link cable internals, and solder PIN 5 to either or both of the GROUND pad on the link cable internals. I bridged the two ground points and soldered one wire to the bridged pads.
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GC PIN OUT
PIN 1 = 5 VOLTS
PIN2 = 5 VOLTS GROUND
PIN 3 = DATA
PIN 4 = NOT USED
PIN 5 = 3 VOLTS GOUND
PIN 6 = 3 VOLTS
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From the link cable internals, desolder the GBA EXT LINK male connector. Clean off the 6 points and add a bit of fresh solder.
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Cut one end off of the GBC link cable. It doesn't matter which end you use, what matters is that the 4 pins on the end of the GBC cable are placed in the exact same spot on the internals of the GBA to GC link cable.
Strip end of the 6 internal cables. Use a multimeter to pin-out your GBC link. Depending on which side you are using, your cable may pin out differently. They are not the same on either side, so one cable will have two ends with two different pin outs, but both sides can be used if you wire it correctly.
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In the diagram above I show with colors which PIN should be soldered to what pad on the board.
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This portion below is theoretical and not entirely tested, so please contact me if you think this is potentially harmful to the GB or GC, but through my testing, it seems to be low voltage, and just enough to keep the device on and charge the device.
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It seems you can solder a USB-C male port to 5V & 5V GROUND to charge the SP from the same port on the console. It seems to be pushing out 4.99V at .1A-.15A. Review the pinout below. This is also dependent on the gauge wire used, length of wire, etc. I need to do more testing and update with a V2. I plan to use a MT3608 DC-DC Step Up Boost Power Converter to boost the power a bit - just enough to match my PCs USB power output. This has been tested but not put into a fully working unit. ​
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I housed all of this into the mentioned RocketFish GC wireless controller receiver, using sandpaper, an airbrush and some paint to change the shell.
The housing had a hole conveniently placed in the center for the now removed pairing button. I opened this a few millimeters to fit the GX12-6 aviation cable using a small metal file and rotary tool.
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If you made it this far, thanks for reading and happy modding. Please feel free to reach out for assistance, questions or feedback!