numpad hackpad case schematic pcb BOM Seeed XIAO RP2040 -1 Through-hole 1N4148 Diodes -9 MX-Style switches -9 EC11 Rotary encoders -1 0.91 inch OLED displays -1 SK6812 MINI-E LEDs -9 M3x16mm screws -8 M3x5mx4mm heatset inserts -8