Overview
The HC-05 is a serial Bluetooth module that enables wireless communication between microcontrollers, PCs, or smartphones. It’s ideal for Arduino, Raspberry Pi, ESP32, and STM32 projects, allowing data exchange over Bluetooth 2.0. The module supports Master/Slave mode, making it versatile for IoT, robotics, and STEM lab experiments.
Key Features
Bluetooth Version: 2.0 + EDR (Enhanced Data Rate)
Modes: Configurable as Master or Slave
Communication: UART serial interface for easy microcontroller integration
Range: 10 meters (typical), line-of-sight
Voltage: 3.3–5V logic compatible
LED Indicator: Shows connection status (blinking = searching, steady = connected)
Technical Specifications
| Parameter | Specification |
|---|---|
| Operating Voltage | 3.3–5 V DC |
| Operating Current | 30–40 mA (connected) |
| Standby Current | <1 mA |
| UART Logic Level | 3.3 V (5V tolerant) |
| Baud Rate | Default 9600 bps (configurable 1200–1382400 bps) |
| Wireless Range | ~10 meters (can be extended with external antenna) |
| Communication Mode | Asynchronous serial UART |
| Bluetooth Profile | SPP (Serial Port Profile) |
| Default Role | Slave (can be changed to Master using AT commands) |
Pinout
| Pin | Function |
|---|---|
| EN / Key | Enter AT command mode (high = AT mode) |
| VCC | Power supply 3.3–5 V |
| GND | Ground |
| TXD | Transmit data (connect to microcontroller RX) |
| RXD | Receive data (connect to microcontroller TX) |
| STATE | Connection status indicator (HIGH when connected) |
Applications
Wireless serial communication between microcontrollers
Remote control of robots and devices
Bluetooth-based IoT sensors
Data logging to smartphones or PCs
STEM education projects for hands-on wireless communication labs
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