Designing the MonkiiBoard58

Everything else follows from the MCU, so start there. We chose the ESP32-S3-WROOM-1 because it does Bluetooth LE, Wi-Fi and native USB with no extra chips, and has plenty of GPIO for a 5×12 matrix, an encoder and a screen. We would suggest the module over a bare chip: it is pre-certified and saves you drawing an RF front end.

A wireless board runs from a battery and charges over USB, so this section does both. USB-C brings in 5V, a TP4056 charges the cell, an SPDT switch cuts the battery entirely, and an AMS1117 drops it to a steady 3.3V. One detail worth copying: CC1 and CC2 each need their own 5.1kΩ resistor to ground, never a shared one.

Fifty-eight switches, each with a diode, is the slow part. The trick is net labels: draw one switch-and-diode pair, label the diode ROW0 and the switch COL0, then copy-paste and change the labels. You never drag a wire across the sheet. It is 5 rows by 12 columns, with two positions left empty under the wide keys, which is how 60 becomes 58.

An OLED left running will flatten a battery overnight, so we did not wire it straight to 3.3V. A P-channel MOSFET sits between the rail and the screen, and one GPIO opens that gate, so the firmware can cut the display when the board sleeps. A 10kΩ pull-up keeps it off at power-on. The encoder is simpler: two pins for rotation, one for the push.

With the schematic done, export the netlist and import it into the PCB editor. Every footprint lands in one heap with thin lines showing what has to connect to what, and nothing is where it belongs yet. This is the least promising a board ever looks, so do not read anything into it. Check the count matches what you drew, then start dragging.

Now place properly: power near the USB-C connector, MCU central, matrix where the keys physically are. The one rule you cannot bend is the module's antenna end, which needs a keep-out with no copper on any layer, no ground pour, nothing underneath. Pour over it and your range drops to almost nothing.

Run ERC on the schematic and DRC on the board, and clear every error rather than filing it away. Most ERC complaints are just missing PWR_FLAG symbols or unused pins wanting a no-connect marker. Then assign footprints, export Gerbers and open them in a viewer before uploading. A fab run costs money and takes weeks, so this is the cheapest twenty minutes of the project. Our output is on GitHub to compare against.