ESP32 Sensor Node — MCU + I2C Sensor + Analog Signal Conditioning Board

A compact ESP32-based sensor node designed in KiCad, combining digital (I2C) and analog signal acquisition on a single board. Built to demonstrate correct practices in decoupling, bus pull-up sizing, and analog front-end design.

Overview

This board integrates an ESP32-WROOM-32 microcontroller with a BME280 environmental sensor over I2C, alongside an analog input channel conditioned through an MCP6002 op-amp buffer for NTC thermistor readings. USB-C provides power and a CH340C USB-to-UART bridge handles programming/serial communication.

Key Design Features

• MCU: ESP32-WROOM-32
• Digital sensing: BME280 (temperature, humidity, pressure) via I2C, with properly sized pull-up resistors
• Analog front-end: NTC thermistor input buffered through an MCP6002 op-amp for stable ADC readings
• USB interface: USB-C connector, CH340C USB-to-UART bridge for programming and serial debug
• Power regulation: AP2112K-3.3 LDO regulator
• Schematic verified: Passed Electrical Rules Check (ERC) with 0 errors, 0 warnings (one documented exclusion on BME280 SDO pin, intentionally tied to GND to set the I2C address)
• Fully routed 2-layer PCB layout with defined board outline

Repository Contents

• ESP32_Sensor_Node.kicad_sch — Schematic (KiCad 10)
• ESP32_Sensor_Node.kicad_pcb — PCB layout
• ESP32_Sensor_Node.kicad_pro — Project file
• Design rules and project settings

Purpose

This project was built to reinforce and demonstrate core mixed-signal PCB design skills: correct decoupling capacitor placement, I2C bus design, and analog signal conditioning — skills directly applicable to embedded hardware and IoT sensor product design.