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Open-Source Board Design Research

A curated collection of open-source KiCad board designs that share components, circuits, or design goals with the Dilder custom PCB. Each project is analyzed for what we can learn from it, with images of the actual board layouts and schematics.

All designs have been cloned into the project's hardware-design/reference-boards/ directory and can be opened directly in KiCad.

Why Study Other Boards?

Designing a custom PCB from scratch is hard. Studying existing open-source boards lets us:

  • Validate our circuit design against proven, manufactured boards
  • Learn routing techniques for tricky components (USB differential pairs, antenna keep-out zones, ground planes)
  • Copy proven power management circuits rather than designing from first principles
  • Verify component choices against what others have successfully manufactured at JLCPCB/PCBWay
  • Avoid common mistakes that others have already debugged

Each design below is analyzed for its relevance to the Dilder board (ESP32-S3, e-ink display, LiPo battery, joystick input, IMU sensor).

ESP32-S3 Designs

Ducky Board — ESP32-S3 + e-Paper + Battery Charger

Closest match to the Dilder board

Ducky Board — assembled PCB with 1.52" e-ink display
Ducky Board assembled and running — ESP32-S3 module with 1.52" 3-color e-ink display, USB-C, and LiPo charging. Photo from the project repo.
Attribute Details
MCU ESP32-S3 module
Display GDEM0154Z91 (1.52" e-ink, 3-color, Good Display)
Power USB-C input, integrated Li-Ion battery charger with status LEDs
Design tool KiCad 9
License GPL-3.0
Source MakersFunDuck/Ducky-board-ESP32-S3
Local path hardware-design/reference-boards/esp32s3-ducky-epaper/
KiCad files hardware.kicad_sch, hardware.kicad_pcb, hardware.kicad_pro

What to Study

  • Battery charging circuit — The Ducky Board integrates a single-cell Li-Ion charger with charge status LEDs, the same architecture as the Dilder's TP4056 + DW01A design. Compare their component choices with ours.
  • ESP32-S3 power sequencing — How the module's EN pin is handled, decoupling cap placement, and 3.3V regulation.
  • e-Paper display connector — How the display is interfaced via SPI, including the DC/RST/BUSY control line routing.
  • USB-C implementation — CC pull-down resistors, VBUS protection, and data line routing.
  • Board form factor — Compact breakout form factor optimized for the e-ink display footprint.

Files Available

  • hardware.kicad_sch — Full schematic with all component values
  • hardware.kicad_pcb — Complete routed PCB layout
  • Schematic.pdf — Exported schematic for quick viewing without KiCad
  • PCB.pdf — PCB layout export

Basic ESP32-S3 Dev Board — Minimal Reference Design

ESP32-S3 Basic Dev Board — 3D render
3D render of the basic ESP32-S3 dev board — ESP32-S3-WROOM-1 module, USB-C, LDO regulator, reset/boot buttons, status LEDs, all GPIO broken out to castellated pads.
ESP32-S3 Basic Dev Board — PCB layout
PCB layout — note the clean routing, USB-C at the bottom edge, ESP32-S3 module centered with antenna pointing off-board, decoupling caps close to power pins.
Attribute Details
MCU ESP32-S3-WROOM-1 module
Features USB-C (with 5.1k CC pull-downs, differential pair routing), 3.3V LDO, reset/boot buttons, 3 status LEDs (5V, 3.3V, GPIO blinker), all GPIO broken out
Design tool KiCad
License MIT
Source atomic14/basic-esp32s3-dev-board
Local path hardware-design/reference-boards/esp32s3-basic-devboard/

What to Study

  • USB-C done right — This is the cleanest ESP32-S3 USB-C implementation in our reference collection. The 5.1k CC1/CC2 pull-downs, differential pair routing for D+/D-, and series resistors are all textbook. Compare directly with the Dilder's USB-C circuit.
  • LDO selection and placement — Uses an LD117 with proper input/output decoupling. Shows recommended cap values and placement distance from the IC.
  • Antenna keep-out — Note how the PCB copper is cleared around the ESP32-S3 antenna area (top-left of the module). The Dilder board must maintain this same keep-out zone.
  • GPIO breakout pattern — Castellated edge pads with clear silkscreen labeling. Good reference for our e-Paper header connector placement.

Files Available

  • dev-board.kicad_sch — Schematic (also exported as PDF)
  • dev-board.kicad_pcb — PCB layout (also exported as SVG)
  • docs/dev-board.step — 3D STEP model for mechanical integration
  • docs/schematic.pdf — Printable schematic

Official Espressif KiCad Libraries

Attribute Details
Contents Symbols, footprints, and 3D models for ALL Espressif chips and modules
Includes ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6, ESP32-H2 — bare chips, WROOM modules, MINI modules, and DevKit boards
License Apache-2.0
Source espressif/kicad-libraries
Local path hardware-design/reference-boards/espressif-kicad-libs/

What to Study

  • Authoritative footprints — These are the official pad dimensions, pin assignments, and courtyard sizes for the ESP32-S3-WROOM-1-N16R8. If our custom KiCad footprint differs from these, the official version is correct.
  • Antenna keep-out zones — The footprint includes the manufacturer-specified copper keep-out for the PCB antenna.
  • 3D models — STEP files for mechanical clearance verification in the 3D-printed enclosure.

Installation

These libraries can be installed automatically via KiCad's Plugin and Content Manager (PCM). Search for "Espressif" in the PCM. The local copy in this repo is for offline reference.

RP2040 / Pico Designs

Reverse-Engineered Pico with USB-C

Attribute Details
MCU RP2040 (standard Pico), RP2040 + CYW43439 WiFi (Pico WH), RP2350 (Pico 2)
Features Faithful reproduction of the official Raspberry Pi Pico circuit in KiCad, upgraded with USB-C
License WTFPL (unrestricted — do anything you want)
Source sabogalc/project-piCo
Local path hardware-design/reference-boards/rp2040-pico-usbc/

What to Study

  • Official Pico circuit — This is the most faithful KiCad reproduction of the Raspberry Pi Pico. The original design files are in Cadence Allegro (proprietary); this project reverse-engineered them into KiCad. Use this to understand the RP2040's power path: how VSYS, VBUS, and the Schottky diode interact.
  • WiFi variant (Pico WH) — The Pico WH sub-project includes the CYW43439 WiFi/BLE chip wiring — useful for understanding how the Pico W differs from the standard Pico at the circuit level.
  • USB-C upgrade — Shows how to replace micro-USB with USB-C on an RP2040 board while maintaining the same power path.

Sub-Projects

Folder Board Notes
KiCad Projects/Pico C/ Standard Pico with USB-C RP2040 + W25Q16 flash
KiCad Projects/Pico WH - No License/ Pico WH with USB-C RP2040 + CYW43439 WiFi/BLE
KiCad Projects/Pico 2 C/ Pico 2 with USB-C RP2350 (next-gen)

Each sub-project contains exported schematic PDFs for quick viewing without opening KiCad.

RP2040 Minimal Design (JLCPCB-Ready)

Attribute Details
MCU RP2040 (bare chip — not a module)
Origin Raspberry Pi's official "Minimal Viable Board" example, ported to KiCad 7 with JLCPCB assembly files
License BSD-3-Clause
Source tommy-gilligan/RP2040-minimal-design
Local path hardware-design/reference-boards/rp2040-minimal-jlcpcb/

What to Study

  • Absolute minimum RP2040 circuit — This is the smallest possible working RP2040 board: just the chip, a 12MHz crystal, a W25Q16 flash chip, decoupling caps, and USB. Nothing else. Use this to understand which components are mandatory for the RP2040 to boot.
  • JLCPCB compatibility — Includes BOM and CPL files formatted for JLCPCB's assembly service. Good reference for how to export and format assembly files from KiCad.
  • Contrast with the Dilder's ESP32-S3 approach — The bare RP2040 requires ~15 external components (crystal, flash, caps, resistors). The ESP32-S3-WROOM-1 module integrates all of this, which is why the Dilder switched MCUs.

RP2040 Hardware Design Guide

RP2040 Design Guide — KiCad schematic
Full RP2040 schematic from the design guide — RP2040 chip, crystal, flash, voltage regulator, USB, and GPIO breakout. All component values and LCSC part numbers annotated.
RP2040 Design Guide — PCB front render
Front side — RP2040 chip centered, USB at top, GPIO pins along both edges. Green solder mask with ENIG (gold) finish.
RP2040 Design Guide — PCB back render
Back side — ground plane with thermal reliefs around component pads. Silkscreen shows pin labels and design info.
Attribute Details
MCU RP2040 (bare chip)
Features Complete design guide with component selection rationale, custom KiCad libraries, schematic PDF
License MIT
Source Sleepdealr/RP2040-designguide
Local path hardware-design/reference-boards/rp2040-designguide/

What to Study

  • Component selection rationale — The README explains why each component was chosen: XC6206 LDO for low quiescent current, specific 12MHz crystal for JLCPCB availability (C9002), flash chip options. This reasoning applies to any microcontroller board design.
  • Custom KiCad libraries — Includes purpose-built symbols and footprints in PCB/Libraries/. Useful if you need to create custom footprints for components not in KiCad's default libraries.
  • Ground plane strategy — The PCB renders show solid ground plane coverage with proper via stitching. Good reference for the Dilder's inner ground plane (In1.Cu).
  • Includes official Pico datasheets — The Pico-Resources/ folder contains the official Pico schematic PDF, RP2040 datasheet, and the hardware design guide PDF from Raspberry Pi.

Virtual Pet Designs

OpenTama — Tamagotchi Reference Board (JLCPCB-Ready)

Same product category as Dilder

OpenTama PCB layout — egg-shaped board
OpenTama v1.1 PCB layout — egg-shaped board with STM32L072 MCU, SSD1306 OLED and UC1701x LCD connectors, 3 buttons, buzzer (LS1), battery connector, and SWD debug header. All components on one side for JLCPCB assembly. Note the Sparkr bunny logo in the silkscreen.
Attribute Details
MCU STM32L072 (ARM Cortex-M0+, ultra-low-power)
Display SPI SSD1306 OLED (128x64) or SPI UC1701x LCD
Battery 1000mAh LiPo (40x30x12mm) — same capacity as Dilder
Input 3 tactile buttons (SW1-SW3)
Audio Piezo buzzer (LS1)
Protection Battery over-discharge/charge protection circuit
Design tool KiCad
License CERN-OHL-S v2 (open hardware — permits derivative works)
Source Sparkr-tech/opentama
Local path hardware-design/reference-boards/opentama-virtual-pet/
Blog Design notes

What to Study

  • Battery protection circuit — Uses DW01A + FS8205A — the exact same protection ICs as the Dilder board. Compare their schematic implementation with ours to verify our circuit is correct. This is the most directly applicable reference we have for the battery protection subsystem.
  • JLCPCB assembly optimization — All components placed on the top side for single-side assembly. LCSC part numbers pre-assigned for every component. The designer notes that "JLCPCB references for all the components have been provided."
  • Single-side placement — The egg-shaped PCB places everything on one side, matching JLCPCB's Economic PCBA service (which only supports single-side SMT). The Dilder board follows the same constraint.
  • Button debouncing — Simple button input circuit with hardware debounce. Compare with the Dilder's software debounce approach (200ms in firmware).
  • Buzzer integration — Shows how to wire a piezo buzzer to a GPIO pin with appropriate series resistor. Directly applicable to the Dilder's planned Phase 7 audio output.
  • Form factor — The egg shape is creative but the component density and routing strategies work for any small board. Pay attention to how traces route around the button footprints.

Component Overlap with Dilder

Component OpenTama Dilder Same?
Battery protection IC DW01A DW01A Yes
Protection MOSFET FS8205A FS8205A Yes
Battery capacity 1000mAh 1000mAh Yes
Battery connector JST PH 2.0mm Molex 1.25mm Different
MCU STM32L072 ESP32-S3 Different
Display interface SPI SPI Same protocol

Comparison Matrix

Feature Ducky Board ESP32-S3 Basic OpenTama RP2040 Minimal RP2040 Guide Pico USB-C
MCU ESP32-S3 ESP32-S3 STM32L072 RP2040 RP2040 RP2040
Display e-Paper None OLED/LCD None None None
Battery Li-Ion charger None LiPo + protection None None VSYS input
USB USB-C USB-C Micro-USB USB USB USB-C
Joystick/Input None None 3 buttons None None None
IMU None None None None None None
JLCPCB-ready Likely No Yes Yes No No
License GPL-3.0 MIT CERN-OHL-S BSD-3 MIT WTFPL

The Dilder board combines elements from multiple references: ESP32-S3 core from the Ducky/Basic boards, battery protection from OpenTama, USB-C from the Basic dev board, and JLCPCB manufacturing approach from both OpenTama and the RP2040 Minimal design.

How to Open These Designs

  1. Install KiCad 7+ — all projects are KiCad 7 or later format
  2. Navigate to hardware-design/reference-boards/<project>/
  3. Open the .kicad_pro file — this loads both the schematic and PCB
  4. Schematic: Tools > Schematic Editor to view the circuit
  5. PCB: Tools > PCB Editor to view the board layout
  6. 3D View: In the PCB editor, press Alt+3 to see a 3D render

Quick viewing without KiCad

Most projects include exported PDFs of schematics in their docs/ folder. Open these for a quick look without launching KiCad.

Sources