June 10th 2020
Surgically implanting a 3D-Touch Capacitive Trackpad in place of the original Analog Joystick.
It’s 2020 and in the pandemic boredom it’s no easy job to survive from creativity suppression. But… when you realize that you own a toolbox with a plenty of electronics inside, it’s not so hard to see the same old things lying on the desk, in a different way. It’s the case of my Nintendo Switch: I never had the occasion to disassemble the Joy-Con controller before. What a wonderful occasion to put hands on its inside and start a new journey.
“Well, let me look at the internet if someone crazy like a horse had the insane idea to replace the good old Analog Joystick with a Capacitive Trackpad” — No results found.
I am used to start sketching ideas on a notepad and here is my first drawing about how I imagined the Joy-Con with a Capacitive Trackpad in place of the original Analog Joystick.
Then, I re-assembled the Joy-Con and tested it directly with the Switch in order to check that everything worked fine.
Alright, I have to replace an analog potentiometer with a digital one.
Now it’s time to perform some tests.
The whole testing setup involved:
-  1 x Micro-controller
-  2 x 12-bit, voltage output Digital-to-Analog Converter (connected via I2C)
-  1 x 5-Positions 0.5mm Pitch FPC connector for the Analog Joystick
-  1 x 5-Positions 0.5mm Pitch FPC flexible flat ribbon cable
-  1 x 12-Positions 0.5 mm Pitch FPC connector the Capacitive Trackpad
-  1 x 12-Positions 0.5mm Pitch FPC flexible flat ribbon cable
-  1 x Digital 3D-Touch Capacitive Trackpad (connected via I2C)
Since the DACs have a resolution of 12 bits, they accept a value range that goes from 0 to 4095, so I passed it through a loop by steps of 10.
On the Switch console side, I fired up the the Control Stick Calibration utility from the main settings, in order to see if something was gonna happen.
The Capacitive Trackpad is an interesting piece of electronics hosted in a very small and versatile form factor. Surprisingly, it also offers an amazing resolution of 2048 x 1535 x 63 (X x Y x Z) — and yes it has 63 levels of pressure sensitivity (I’ll exploit this feature later in order to digitally emulate the Stick-Button press of the Analog Joystick).
About the pushStick(); method call instruction, since the corresponding pin on the Joy-Con side handles a simple close-circuit logic, I could emulate the button press via code.
Cool. The final result of the first prototype looked to me very promising.
Alright. We have a plane here, now we’d let it fly.
The following step I had in mind, was to create an embedded and more portable solution of the first prototype.
I fired up my faithful KiCad, I drew the schematics and then placed all the components at their place in a quite obsessive-compulsive (dis)order.
Punctual as usual, the courier brought the green gold alongside with the other components.
Testing with the digital multimeter.
The PRO MINI needed to be alimented: I stole all the milliamps needed directly from the main board, siphoning them from an uncovered solder pad.
The main idea was to stick the board directly to the Joy-Con’s back with a professional double-sided tape, make a hole in the plastic shell and then pass all the cables through it.
Since the power implied in alimenting the PRO MINI relies directly on the Joy-Con’s battery, I decided to add a small switch in order to turn off the implant while not in use, avoiding extra drains.
Safety first: I covered all the exposed electronics with a good piece of Kapton tape, in order to don’t short-circuit anything while your hand’s sweating.
And here we go. That’s how it looks in the end. It’s still portable, so it is possible to use it attached or in wireless mode.
Let’s see it in action.
Enjoy the world’s first Nintendo Switch Joy-Con controller with a 3D Capacitive Trackpad.
Doing things more seriously: in my plans there’s the idea to miniaturize the whole circuitry in order to create a smaller PCB that could suit directly inside the Joy-Con controller in place of the Analog Joystick small box that’s approximately 19 x 16 x 4 mm in size.
As you can see, the job is already ongoing.
I am aware that this could arouse interest in a small niche of fanatics, modders and gamers but its HARDWARE stuff, and it costs. This project implies a good amount of work that I’ll be happy to do with your support.
This is explicitly a call to action. If you want to make this Joy-Con Touch Mod-Kit real,