KiCad 9: Design & assemble an ESP32 IoT 4-layer PCB

Project Introduction

This ESP32-based board is brimming with an array of sensors, precision circuitry, and a compact design—perfect for running local inference, classification, and decision-making algorithms. Thanks to the dual-core processing power of the ESP32 and its built-in Wi-Fi/Bluetooth connectivity, this board is designed to accelerate the next wave of smart, connected devices. Whether you're building an intelligent home assistant or a precision agricultural monitor, this platform can handle real-time inference, classification, and decision-making right at the edge—no cloud required.

Throughout the design process, I explore the new features of KiCad 9 RC1 and RC2, from schematic creation to layout and preparation for manufacturing, highlighting how these tools streamline PCB development.

Summary of Features

• Microcontroller: ESP32-C3 with Wi-Fi and BLE connectivity.
• Power: USB-C input, LiPo battery connector, onboard 3.3V and 5V regulation.
• Storage: MicroSD card slot and SPI flash memory.
• Sensors: BME280 environment sensor, ambient light sensor, microphone with pre-amplifier.
• Interfaces: I2C, SPI, USB-to-UART bridge for communication.
• User Interaction: Boot and reset buttons, GPIO header, and status LEDs.
• Design: 4-layer PCB with optimized layout, test points for debugging.

Potential Applications

• Smart Home Monitoring: Use temperature and humidity sensors combined with machine learning to detect anomalies (e.g., a sudden spike in temperature) and issue real-time alerts to keep your home safe and comfortable.
• Environmental Data Analysis: Collect and analyze air quality metrics on the board itself, classifying different pollution levels for real-time alerts and insights, reducing reliance on remote servers.
• Activity Recognition: Use sound and light sensors and AI models to recognize human activities or patterns, enabling intelligent automation (e.g., turning off lights when rooms are unoccupied).
• Predictive Maintenance: Incorporate vibration or current sensors to monitor industrial machinery, then use classification algorithms on the ESP32 to detect early signs of wear or malfunction.
• Smart Security Systems: Combine sensor data (motion, light, sound) with AI to recognize suspicious patterns or detect intruders, triggering alarms or notifications without relying on the cloud.

                                                         (This 4-layer PCB board is sponsored by NextPCB)

KiCad 9 introduces new features and improvements that significantly enhance its usability, functionality, and performance compared to KiCad 8. These updates cater to schematic and PCB editors and the 3D viewer. The first thing I noticed was how much smoother and faster certain aspects of the workflow were compared to previous versions. Features like the improved routing tools, copper zone management, and the new layer management UI made designing a 4-layer PCB much more intuitive. The interface feels modern and well-organized, which is especially important for complex designs like this IoT board. KiCad can still improve its usability. I’d like to see in the future is greater integration with team-oriented tools like Cadlab and Github.

Watch Peter Design an IoT PCB in KiCad 9

Want to see these features in action? Follow along as Peter walks through the entire design process—from schematic capture to PCB layout, routing, and fabrication prep—in his detailed tutorial. Some sections are in-depth, but you’re guaranteed to pick up valuable tips!

Learn More: https://techexplorations.com/kicad/kicad-9-designing-a-4-layer-iot-development-board

Youtube Video: https://www.youtube.com/watch?v=LO9AO0XTX3M&t=772s

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About NextPCB & KiCad

NextPCB provides PCB manufacturing and assembly services, focusing on reliability without breaking the bank. With 5 factories in China and over a decade of quick turnaround electronics manufacturing from prototype to mass production, NextPCB serves over 160 countries around the world, pairing dependable electronics hardware with exceptional service.

As a Platinum KiCad sponsor and long-term supporter of the KiCad open-source ecosystem, NextPCB's contribution spans developer funding, and hosting KiCon Asia — the largest KiCad‑focused event in the region. This KiCad Hub brings together all of our tutorials, tools, projects, and community contributions into one place, making it easier for designers of all levels to learn, explore, and build with KiCad.

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