HC-05 Bluetooth Serial Module

The HC-05 is a serial Bluetooth transceiver module built around the CSR BC417 chip, designed to add wireless serial communication to Arduino, Raspberry Pi, and other microcontroller projects. It operates in the 2.4GHz ISM band using GFSK modulation and supports Bluetooth v2.0+EDR, with a maximum data rate of 2.1Mbps. The module can function as either a master or a slave device, allowing it to initiate connections with other Bluetooth devices or wait to be discovered. Communication is handled through a standard UART interface, with a default baud rate of 9600bps in data mode and 38400bps in AT command mode. The onboard button or the EN pin allows switching between data mode and AT command mode for configuration. With an emission power of 4dBm (Class 2) and a sensitivity of -84dBm at 0.1% BER, the module provides a reliable wireless link at distances of approximately 10 meters. It operates on a 3.3V logic level, while the VCC pin accepts 3.6V to 6V DC, making it easy to power from a 5V supply. The compact 28 × 15 × 2.35 mm PCB fits into tight enclosures, and the module is widely used in wireless remote control, IoT data links, and serial cable replacement. This serial Bluetooth module is a practical and cost-effective solution for adding short-range wireless connectivity to embedded systems.