The Espressif ESP-WROOM-02DN4 is a compact Wi-Fi module based on the ESP8266EX SoC, featuring a 32-bit Tensilica L106 CPU up to 160 MHz, 4 MB SPI flash, and an integrated PCB antenna. Supporting 802.11 b/g/n Wi-Fi with WPA/WPA2 security, it operates from 2.7–3.6 V over -40 °C to +85 °C. With GPIO, UART, SPI, I²C, I²S, and PWM interfaces, this 18 × 20 × 3.2 mm SMD module is ideal for low-power IoT applications.