The JDY-31 SPP-C Bluetooth Serial Pass-Through Module is a compact wireless communication module designed to provide transparent UART serial communication between microcontrollers and Bluetooth-enabled devices. Based on Bluetooth 3.0 SPP (Serial Port Profile), the module allows Arduino, ESP32, STM32, Raspberry Pi, and other microcontrollers to communicate wirelessly with Android phones, Windows PCs, and other Bluetooth devices.