Unscrew the four screws holding the plastic back plate and metal mid plate, and pull both out.
Next you'll trim the excess NeoKey PCBs away, leaving just the 4x4 matrix needed for the 16-key pad.
Use pliers to carefully snap off the top and bottom mounting strips.
Then, use your hands to carefully wiggle the extra two columns off.
Finally, remove the extra row.
Remember to save these extras somewhere safe, you can use them for another project later!
Follow the guide and photos below to wire up the four colums, four rows, power, ground, and NeoPixel data line.
Start by wiring the power, ground and columns. I used thin, silicone covered wire, which is nice and flexible. It is thin enough to thread through the PCB holes without first stripping the insulation, which makes it easier to "tighten" things to even lengths all at once.
After that you will cut, strip, and solder.
Solder to the PCB
Trim, strip and solder the wires on the PCB now. Then, you'll pull the wires to length on the QT Py side of things.
Now you can place the QT Py toward the center of the PCB and pull the wires to even lengths with a little bit of slack.
Solder to QT Py
With the wires tightened up, you can now trim, strip, and solder them to the QT Py as shown here.
Add Switches to Plate and PCB
Click your switches into the plate and then into the PCB. Be mindful of the orientation and check that the legs line up with the sockets before pushing switches into place.
USB Port Extension
Use the short DIY ribbon cable and straight USB port and jack to create an easy to use connector. This fits very nicely compared to the QT Py, which will not lay flush at the port end of the case due to the keyswitch sockets.
Use an adhesive square or double stick foam tape to adhere the bottom of the USB port extender to the metal mid-plate as shown. This will make the port stable enough for plugging and unplugging the USB cable.
Make sure not wires or ribbon cable are pinched by the plate as you close it.
Screw the back plate into place. Don't crank down too hard on the screws or you may risk cracking the plastic back plate.