Handling Wires
I suggest using tweezers to handle the bits of wire. When soldering wires to things, they can get hot so this helps keep your fingers from getting burnt. Tweezers also help while soldering – You can get a better grip and get in close quarters.
Connecting Ground
Attach two wires to one of the ground electrodes on one of the arcade buttons. For a 2x2 button layout, it didn't matter which button was first, but depending on your layout, you may want the first button to be closest to the Adafruit Feather board. Using the tip of the soldering iron, heat up the tinned electrode and place the two wires while the solder is molten.
Share Ground
With the two wires attached to the electrode, grab one of the wires and position it near the next arcade button. Grab another wire and hold both in place using the tweezers. Make sure the tips are very close to each. Place the two tips over one of the ground electrodes on the arcade button. Heat up the tinned electrode using the tip of the soldering iron while the two wires are touching to solder them together. Let the solder solidify before releasing the wires. We'll need to repeat this process for all the ground connections.
Ground Continued
When you've reached the last button, you'll need to jump to the second ground electrode – this will be either the LED or momentary switch, depending on which ever you started. Following the same process, repeat the steps to wire all of the ground electrodes together. When you've reached the last arcade button, you may need a fashion a longer wire in order to connect to the Adafruit Feather board.
LED Wires for Anode
Next we'll need to make some new wires for connecting the anode's on the LEDs to the Adafruit Feather. We'll basically repeat the process like we did for all of the ground connections. We'll need to measure, cut, strip and tin all of the wires. These wires will not be shared and will connect to analog pins individually.
Solder LED Anode Connections
With all of the wires measured, cut, stripped and tinned, we can then attach them to the electrodes on the arcade buttons. Make sure you're connecting to the anodes of the LEDs. Connect the wires by soldering them to the electrodes.
Button Wires for Signal
Next we'll need to make some new wires for connecting the momentary switch on the arcade buttons to the Adafruit Feather. Following the same process like we did for the ground and voltage wires, repeat this process. We'll need to measure, cut, strip and tin all of the wires.
Solder Switch Wires
With all of the wires measured, cut, stripped and tinned, we can then attach them to the electrodes on the arcade buttons. Make sure you're connecting to the electrodes on the momentary switch. It should be the only remaining electrodes. Connect the wires by soldering them to the electrodes.
Connecting Wires to Adafruit Feather
OK now that we have all of our electrodes wired up, it's time to get them connected to the Adafruit Feather. Grab the cover with the Feather board secured to it and position it near the button box. Pick out the wires and check to ensure they can reach the pins on the Adafruit Feather. If you've left the wires extra long, great! We can trim those up now. If they aren't long enough, you might have to recut longer wires and connect those.
Connect Ground to Feather
The first connection we should make is the common ground wire coming from the buttons. There's a number of available ground pins on the Adafruit Feather, pick the one that best suits the location of the wire. Apply solder to your chosen ground pin to tin it. Then, insert the tip of the wire into the pin while keeping it heated with the soldering iron.
Solder Wires to Feather
Lastly, we'll connect all of the wires from the buttons to the Adafruit Feather. If your button has a specific layout, you'll need to map out the wires to their corresponding pins. You'll need to solder the LED wires to the analog pins on the Feather (A1–A5). Then, solder the switch wires to the digital pins (D12, D11, D10, D9, D6, D5).
Wired Connections
Once all of the wires have been soldered, double check to ensure they have a solid connection. Also a good idea to note which pins each button if wired to. If you found the wires are too long, you can shorten them – This will help keep the things inside the box manageable.
Close It Up
Now it's time to close it all up! Make sure to orient the Feather so the microUSB port is facing the cutout on the side of the case. Bring the two pieces together and make sure all of the wires are fitted inside the case. The lip on the cover will snap into the case. Little nubs run across the inner lining walls of the case will fit into indentations on the lip of the case. They'll lock in place when pressed together and you'll hear a satisfying "clicking" sound.
Make, Modify, Share
Congratulations! You've built your very own DIY USB HID keyboard. Did you modify it? What are you using it for? Let us know! Tag @adafruit on your favorite social network and use hashtag #adafruit so we can find it! We love sharing project makes from the community on our social channels.
If you have any technical questions, please post them up on our forums, we have a dedicated team of support engineers who are there to help!
