Another split macropadThis is the largest keypad you can fit within the 100mm x 100mm PCB size. Most PCB manufacturers have special pricing for boards under 100mm square. EasyEDA and JLCPCB will produce 10 pieces for $2 (plus shipping).
This is a 5x5 matrix and has the circuitry to make a split keyboard. It uses the same Sparkfun TRRS jack as the foobar and 6lit. It is a sandwich design with M2 Spacer and screws. PCB mount switch are required as there is no plate.
The split firmware is on github. The gerber files are here.
The top and bottom of the PCB.
Setup as as split keyboard.
Side view showing the M2 Spacers and screws.
The bottom is a second PCB.
The underside of the main PCBs. The orientation of the Pro Micro's is critical.