ESP32-WROOM-32 USB Development Board

A complete 2-layer ESP32-WROOM-32E development board designed in KiCad, integrating USB-to-UART programming, protected USB power input, 3.3 V regulation, BOOT/RESET control, GPIO expansion, and protected I²C interfaces.

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Overview

This project presents the complete hardware design of a compact ESP32-WROOM-32E development board, including schematic capture, component selection, PCB layout, power distribution, interface protection, signal connectivity, design-rule verification, and manufacturing-data generation.

The design combines a Micro-USB interface, USB-to-UART bridge, regulated 3.3 V power architecture, ESP32 boot and reset circuitry, GPIO expansion headers, and protected I²C connectivity into a single 2-layer PCB.

The complete design package includes the KiCad schematic and PCB source files, bill of materials, manufacturing outputs, design documentation, PCB layout views, 3D board views, and verification records.

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Key Features

• ESP32-WROOM-32E based embedded hardware platform
• Micro-USB connectivity for power and USB communication
• CH340E USB-to-UART bridge powered from the +3.3 V rail
• AP2112K-3.3 low-dropout voltage regulator
• Protected USB power input with resettable fuse
• Dedicated USB ESD protection
• BOOT / GPIO0 programming control
• EN / RESET control
• GPIO expansion through dual 14-pin headers
• GPIO21 / GPIO22 dedicated to I²C SDA / SCL
• 4.7 kΩ I²C pull-up resistors
• AXGD10603NR low-capacitance ESD/TVS protection on I²C lines
• Local IC decoupling and bulk power filtering
• ESP32 antenna-region and RF keepout consideration
• 2-layer PCB layout
• Complete KiCad schematic and PCB source files
• Bill of Materials (BOM)
• Gerber and drill manufacturing outputs
• Electrical Rules Check (ERC) completed
• Design Rules Check (DRC) completed

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Project Specifications

Parameter	Specification
MCU / Module	Espressif ESP32-WROOM-32E-H4
USB Connector	Micro-USB, Molex 105017-0001
USB-UART Bridge	CH340E
CH340E Supply	+3.3 V
Voltage Regulator	AP2112K-3.3
USB ESD Protection	SP0503BAHT
I²C ESD Protection	2 × AXGD10603NR
I²C SDA	GPIO21
I²C SCL	GPIO22
I²C Pull-ups	4.7 kΩ to +3.3 V
Logic Voltage	3.3 V
PCB Layers	2
PCB Thickness	1.6 mm nominal
Board Dimensions	51.75 mm × 31.00 mm
CAD Platform	KiCad 9.x
Design Verification	ERC + DRC completed
Hardware Status	PCB not yet fabricated

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Functional Architecture

flowchart LR
    USB[Micro-USB] --> ESD[USB ESD Protection]
    ESD --> FUSE[500 mA Resettable Fuse]
    FUSE --> V5[+5 V Rail]

    V5 --> LDO[AP2112K-3.3]
    LDO --> V3[+3.3 V Rail]

    V3 --> ESP[ESP32-WROOM-32E]
    V3 --> UART[CH340E USB-UART]
    V3 --> I2C[I²C Pull-ups]

    UART <-->|UART0| ESP

    BOOT[BOOT / GPIO0] --> ESP
    RESET[EN / RESET] --> ESP

    I2C --> SDA[GPIO21 / SDA]
    I2C --> SCL[GPIO22 / SCL]

    SDA --> ESP
    SCL --> ESP

    ESP --> GPIO[GPIO Expansion Headers]

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Schematic

Schematic

The complete electrical schematic is available as a PDF for detailed review.

📄 View ESP32-WROOM-32 Schematic PDF

The PDF contains the complete electrical design, including:

• USB Micro-B input and power interface
• USB ESD protection
• Resettable USB input protection
• AP2112K-3.3 voltage regulation
• CH340E USB-to-UART interface
• ESP32-WROOM-32E module
• BOOT / GPIO0 control
• EN / RESET circuitry
• GPIO expansion headers
• I²C SDA / SCL interface
• I²C pull-up resistors
• I²C ESD/TVS protection
• Power decoupling and filtering

PCB Layout

The PCB is a compact 51.75 mm × 31.00 mm, 2-layer design with a nominal thickness of 1.6 mm.

Layout View 1

Layout View 2

The PCB layout was developed with consideration for:

• ESP32 antenna region and RF keepout
• USB interface routing
• Power distribution
• Ground return paths
• Local IC decoupling
• Component placement
• Manufacturing clearances
• Board-edge constraints
• Signal routing

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PCB Routing

The completed PCB routing is shown below.

The routing includes:

• USB D+ / D−
• USB-to-UART connections
• ESP32 UART connections
• I²C signals
• Power distribution
• GPIO connections
• Ground connections

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3D Board Views

Front View

Back View

Design Verification

The schematic and PCB were reviewed using KiCad's electrical and physical design verification tools.

Electrical Rules Check (ERC)

ERC was completed to review:

• Power connectivity
• Pin electrical types
• Net connectivity
• Unconnected pins
• Driver conflicts
• Interface connections
• Electrical rule violations

Relevant ERC issues were reviewed and resolved as part of the schematic verification process.

Design Rules Check (DRC)

PCB DRC was completed to review:

• Track clearances
• Pad clearances
• Via clearances
• Board-edge clearances
• Copper constraints
• Solder-mask constraints
• Connectivity
• Manufacturing-rule constraints

The resulting PCB layout was reviewed for unresolved critical DRC violations.

Verification Summary

Verification Item	Status
Schematic ERC	✅ Completed
PCB DRC	✅ Completed
Net Connectivity	✅ Reviewed
Component Footprints	✅ Reviewed
Board Dimensions	✅ Verified
Manufacturing Outputs	✅ Generated

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Manufacturing Data

The repository includes the generated manufacturing data associated with the PCB design.

The manufacturing package contains:

• Gerber copper layers
• Solder-mask layers
• Silkscreen layers
• Paste layers
• Board outline
• Drill files

View Manufacturing Documentation

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Bill of Materials

The project includes a component-level Bill of Materials for the board.

View Bill of Materials

The BOM contains component references, values, footprints, and available part/manufacturer information.

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Repository Structure

ESP32-WROOM-32-USB-Development-Board/
│
├── README.md
├── LICENSE
├── CHANGELOG.md
├── .gitignore
├── .gitattributes
│
├── ESP32-WROOM-32-Schematic-original-export.pdf
│
├── hardware/
│   ├── kicad/
│   │   ├── ESP32-WROOM-32.kicad_pro
│   │   ├── ESP32-WROOM-32.kicad_sch
│   │   └── ESP32-WROOM-32.kicad_pcb
│   │
│   ├── bom/
│   │   └── ESP32-WROOM-32_BOM.csv
│   │
│   └── fabrication/
│       └── gerbers/
│
├── docs/
│   ├── SCHEMATIC.md
│   ├── ARCHITECTURE.md
│   ├── PINOUT.md
│   ├── MANUFACTURING.md
│   ├── VALIDATION.md
│   │
│   └── images/
│       ├── 3d-front.png
│       ├── 3d-back.png
│       ├── 3d_2.png
│       ├── pcb-layout.png
│       ├── pcb-layout-alternate.png
│       └── pcb-routing.png
│
├── project/
│   ├── design-notes.md
│   ├── repository-audit.md
│   └── SHA256SUMS.md
│
└── archive/
    └── original/

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Design Documentation

Document	Description
Architecture	Functional and power architecture
Schematic Documentation	Schematic organization and design blocks
Pinout	GPIO and interface mapping
Manufacturing	Manufacturing-data inventory
Validation	Design verification information
Design Notes	Engineering design notes
Repository Audit	Project package scope and status

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Current Design Status

Status: PCB design package completed

The schematic, PCB layout, component selection, BOM, manufacturing outputs, and CAD-level design verification have been completed.

The PCB has not yet been fabricated or hardware-validated.

The repository therefore documents the CAD design and generated engineering files without claiming measured electrical, RF, thermal, assembly, or production results.

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Tools and Technologies

• KiCad 9.x
• Schematic Capture
• PCB Layout
• Electrical Rules Check (ERC)
• Design Rules Check (DRC)
• Gerber Generation
• Drill File Generation
• Bill of Materials Generation
• 3D PCB Visualization
• USB-UART Interface Design
• Power Supply Design
• ESD Protection
• I²C Interface Design

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License

This hardware design is released under the CERN Open Hardware Licence Version 2 – Strongly Reciprocal (CERN-OHL-S-2.0).

See the LICENSE file for the complete licence terms.