Slimbox with USB-C Port

Intro

This is a modification of the not-so-slimbox by CyberDNIWE (https://www.thingiverse.com/thing:5349287) to accommodate a USB-C port.

For this design a RP2040-Zero was used and such a USB-C Socket with a screw distance of 25mm.

The code and wiring from GP2040-CE was used (https://gp2040-ce.info).

To safe you some time I will summarize all relevant information here:

Get necessary parts

You will need the RP2040-Zero from Waveshare and the mentioned USB-C adapter (e.g. https://amzn.eu/d/5UkxA97).
A hot-glue gun is optional but useful to fix the RP2040-Zero in place.

For soldering you only need a soldering iron, some cables and solder. Optionally for the Ground connections between all switches some bare wire can safe quite some time, e.g. silver plated copper wire like this one https://amzn.eu/d/7TZ6bs7.

Of course you need some switches (at least 15).

Print files

First, print out the necessary parts:
1 x Bot_USB_C
1 x Top_USB_C
4 x Insert
3 x ButtonSmall
11 x ButtonNormal
1 x ButtonBig

The only supports necessary are for Top_USB_C. The top face should face the print bed for best quality and least amount of support structures.

You can use the .3mf files to look at my print settings.

Spend some time cleaning up the prints. I found the inside of the mounting cross of the buttons especially important to make sure they all fit on the buttons later.

Assembly

Press all switches into place (from the top) but not the button caps for now.

Screw in the USB-C extension and connect the RP2040-Zero. Optionally hot-glue the RP2040-Zero in place (make sure you still can reach/solder the pins)

The internal USB-C has to be routed like in the image, otherwise the bottom might not close.

Solder

Prime the pins of the RP2040-Zero with a small amount of solder to make later easier to solder cables to it.

Connect all GND pins of the switches together (you can use any of the two pins of the switch as GND pin). I prefer to use silver plated copper wire for this job.

Connect the common GND of the buttons to the GND of the RP2040-Zero as well. This time use a flexible cable, not a stiff copper wire.

Connect the switches to the RP2040-Zero. I recommend connecting them chronological, starting with GP0. I had to reference multiple websites to find the correct wiring. To save you some time I added an image from the bottom telling which pin connects to which button.

Make sure you don't get too high with the wiring, it should be almost flush with the edge of the part Top_USB_C (see image above taken from an angle).

Flash the firmware

Download the RP2040-Zero firmware from https://gp2040-ce.info/#/download.

Hold down the Boot Button while plugging the RP2040-Zero into your computer. It will display as mass storage device. Copy the downloaded .uf2 file into it. The RP2040-Zero will automatically disconnect and restart. It is now ready to test.

Disconnect the USB-Cable. Press down the B2/Circle button while connecting it into the computer. This will initially set the controller to XInput (see https://gp2040-ce.info/#/usage). Now you can use a program or game to test all buttons. Alternatively it can be set as Nintendo Switch Controller, DirectInput/PS3, PS4 or as keyboard.

When all buttons are working as intended you can finish the assembly.

Use the inserts as guides and assemble both halves. Note that this requires quite some force. I used my fist while the controller was sitting flat on the fable to close all gaps. A rubber hammer might work as well.
In the end put on the button caps.