The UI board has finally passed its steepest mountain —

all potentiometer, ADC, key switch, and I/O expander connections are now fully routed.

This section was particularly challenging:

• 64 analog potentiometers (each with low-pass and reference routing)
• 32 independent key inputs through two MCP23S17 expanders
• Integrated ESD paths, shielding traces, and shared ground planes
• 96 LEDs to coexist in the same grid

After many iterations, I managed to fit everything while preserving:

• Continuous ground on inner layer (L2)
• Reserved space for LED horizontal buses (Bottom layer)

Next, I’ll start routing LED data and power (L3) —
but with the entire input system already verified, I feel the design has crossed its biggest hurdle.