PCB v0.4 — Board Routed, Gerbers Next¶
The Dilder PCB design hit a milestone: v0.4 is fully placed and routed. 30 components on a 30x70mm 4-layer board, 34 nets, 125 pad connections. The board is ready for design rule checks and Gerber export.
From 45x80mm to 30x70mm¶
Between v0.3 and v0.4, the board shrank. The original 45x80mm layout had generous spacing between component zones but wasted board area. By tightening placement — especially in the power section where the TP4056, DW01A, and FS8205A share a compact cluster — we got down to 30x70mm without sacrificing routability.
That's roughly the size of a credit card plus a centimeter. Small enough to fit inside the 3D-printed enclosure alongside the battery and display.
The Layer Stack¶
Four layers, each with a clear job:
| Layer | Purpose |
|---|---|
| F.Cu | Component pads, short signal stubs, GND pour |
| In1.Cu | Continuous ground plane (RF reference + return paths) |
| In2.Cu | 3.3V power distribution plane |
| B.Cu | Long signal runs, additional GND pour |
The unbroken ground plane on In1.Cu is the backbone. It gives the ESP32-S3 antenna its RF ground reference, provides clean return paths for SPI and I2C signals, and keeps the power section quiet. Both ground pours and both planes start below y=5mm to respect the antenna keep-out zone.
Six Zones, Top to Bottom¶
The board is organized into functional zones that follow signal flow:
Zone A (Antenna) — Empty. No copper on any layer. The ESP32-S3-WROOM-1 antenna overhangs the board edge here.
Zone B (ESP32-S3) — The module sits centered with decoupling caps on the left margin and charge/standby LEDs on the right.
Zone C (Power) — AMS1117-3.3 LDO, TP4056 charger, DW01A battery protection, FS8205A MOSFETs, and the JST-PH battery connector. USB-C power enters at the bottom and flows up through this section.
Zone D (Peripherals) — LIS2DH12TR accelerometer (I2C), 8-pin JST-SH ePaper connector (SPI), BOOT and RESET buttons.
Zone E (Joystick) — SKRHABE010 5-way joystick, centered for thumb access.
Zone F (USB-C) — HRO TYPE-C-31-M-12 connector with CC pull-down resistors.
The BOM at $4.26¶
28 unique components, 30 placed (including duplicate passives). Total BOM cost at JLCPCB quantities: ~$4.26 per board. The ESP32-S3 module at $2.80 is two-thirds of that. Everything else is under $0.50 each, most under $0.10.
For comparison, the breadboard prototype using off-the-shelf dev boards costs 40-85 EUR. The custom PCB brings that down to single digits — that's the whole point.
Routing Strategy¶
The routing follows a zone-based approach:
- Power traces are wider (0.5mm+) for current carrying capacity
- SPI signals (ePaper) route on F.Cu with short stubs to the JST-SH connector
- I2C signals route to the LIS2DH12TR with matched-length traces and nearby pull-ups
- USB D+/D- are routed as a differential pair with controlled impedance
- Joystick GPIO lines are simple digital traces with internal pull-ups in the ESP32-S3
The routing scripts use KiCad's pcbnew Python API to set track widths, via sizes, and design rules programmatically. Every trace can be regenerated from code.
What's Next¶
- DRC (Design Rule Check) — run KiCad's checker against JLCPCB's manufacturing constraints
- Generate Gerbers — export fabrication files in JLCPCB format
- Order prototypes — 5 boards from JLCPCB, shipped to Germany
- Assemble and test — hand-solder components, flash firmware, boot the octopus
The board design lives in hardware-design/Board Design kicad/ with the full KiCad project, build scripts, and design documentation. From breadboard to a 30x70mm PCB that costs $4.26 in parts. The octopus is getting its proper home.