ESP32 Smart Access Control System

Summary

This hardware engineering project involved architecting and developing a multi-modal smart access control system from the ground up, targeting the ESP32 microcontroller. The system features three distinct methods of authentication: a physical 4x4 matrix keypad, an RC522 RFID reader, and a secure remote application controller via WebSockets.

To provide real-time user feedback, the system interfaces with a 128x64 OLED display to communicate the lock's current state. The physical actuation is handled by a 12V electromagnetic solenoid lock, safely isolated and triggered via a 5V single-channel relay. The entire firmware architecture was written in bare-metal Embedded C using the Espressif IoT Development Framework (ESP-IDF). Additionally, the device communicates with a custom-built Progressive Web Application (PWA) for remote monitoring and access.

Technical Implementation & Architecture As the sole embedded software engineer on this project, I designed a modular firmware architecture. The high-level state machine, OLED rendering logic, and output signal routing are centralized in the main.c file. To ensure clean hardware-software abstraction, I developed specialized component libraries to control each peripheral independently.

Key engineering highlights include:

• Serial Communication Protocols: Directly interfaced with hardware peripherals by writing drivers for I2C (handling the SSD1306 OLED display) and SPI (managing high-speed data transfer with the RC522 RFID module).
• WebSockets Integration: Implemented a WebSocket client in C to maintain a persistent, bidirectional connection between the ESP32 and a remote server, enabling real-time remote unlocking capabilities via the companion PWA.
• Hardware Integration: Managed GPIO states and real-time processing to safely actuate the 12V solenoid via a 5V relay circuit, utilizing a 1N4007 flyback diode to protect the microcontroller from voltage spikes.

Technologies I used for this project

Main Technologies

• Embedded C
• ESP-IDF (v6.0)
• FreeRTOS (Task Management)

Hardware & Protocols

• ESP32 Microcontroller
• SPI & I2C Protocols
• WebSockets (TCP/IP)
• RC522 RFID Reader & 4x4 Keypad
• 12V Electromagnetic Solenoid

Companion Software

• Progressive Web App (PWA)

Results

The project successfully demonstrates a complete end-to-end IoT embedded system, combining secure peripheral integration, protocol level driver development, and real time state management.