The schematic is your wiring diagram — it shows which pins connect to what. Open KiCad, create a new project, and open the Schematic Editor.
1. Place the microcontroller
Press A to open the symbol chooser. Search for MOUDLE-SEEEDUINO-XIAO (yes, the typo is in the library) and place it on the schematic.
This is the brain of your macropad. Every switch, LED, and encoder connects back to it.
2. Place your switches
Press A again, search for SW_Push, and place one for each key you want. For a simple 3-key pad, place 3 switches.
3. Wire them up
Press W to start drawing wires. Connect one side of each switch to a XIAO pin (pins like D0, D1, D2, etc.) and the other side to ground.
Press P and search for GND to place ground symbols. Attach one to the ground side of each switch and to the XIAO’s GND pin.
4. Matrix wiring (for 4+ keys)
If you have more keys than available pins, arrange your switches in a grid (rows × columns). Each intersection has a switch and a diode:
- Add
1N4148 diodes — search for the D symbol, one per switch.
- Wire each switch’s output through a diode.
- Connect all switches in the same row together, and all switches in the same column together.
- Connect each row wire and column wire to a XIAO pin.
For the diode footprint, use Diode_THT:D_DO-35_SOD27_P7.62mm_Horizontal — this matches the through-hole 1N4148 diodes in your kit.
A 4×4 matrix (16 keys) only needs 8 pins: 4 rows + 4 columns.
5. Assign footprints
Before moving to PCB layout, every schematic symbol needs a physical footprint:
- Click Tools → Assign Footprints (or the footprint assignment button in the toolbar).
- For each component, double-click it and select the correct footprint:
- XIAO: use the footprint from the care package library
- Switches:
MX_Only_1.00u (from the care package)
- Diodes:
Diode_THT:D_DO-35_SOD27_P7.62mm_Horizontal
