HC05-Bluetooth

HC-05 Bluetooth Serial Module

The HC-05 Bluetooth Module is a compact and reliable wireless serial communication device that enables microcontrollers such as Arduino, ESP32, STM32, PIC, or Raspberry Pi to communicate over Bluetooth.

It uses the Serial Port Profile (SPP) to replace wired UART connections with a wireless link, allowing easy data transfer between embedded systems and smartphones, tablets, or PCs.

The module supports both Master and Slave modes, making it ideal for creating wireless control systems, sensor networks, robotics, home automation, and IoT devices.

With simple UART communication and AT command configuration, the HC-05 is perfect for beginners and professionals alike.

✨ Key Features

✅ Bluetooth 2.0 + EDR
✅ Serial UART interface (TX/RX)
✅ Master or Slave mode selectable
✅ Easy AT command configuration
✅ Onboard 3.3V regulator
✅ LED status indicator
✅ Low cost and widely compatible
✅ Works with Android, PC, and microcontrollers

📊 Technical Specifications
🔌 Electrical
Parameter Value
Operating Voltage (board) 3.6V – 6V DC
Logic Level 3.3V TTL
Current (idle) ~8 mA
Current (connected) 30–50 mA
Power Consumption Low
📡 Bluetooth
Parameter Value
Bluetooth Version 2.0 + EDR
Frequency Band 2.4 GHz ISM
Modulation GFSK
Range 8–10 meters
Profile SPP (Serial Port Profile)
Data Rate up to 3 Mbps (theoretical)
💻 Serial Communication
Parameter Value
Interface UART (TX/RX)
Default Baud Rate 9600 bps
Supported Baud Rates 1200 – 1382400
Data Format 8 data bits, 1 stop bit, no parity
📍 Pin Configuration (Pinout)

Most HC-05 breakout boards have 6 pins:

🔹 Pin
EN VCC GND TXD RXD STATE

🔹 Pin Details
Pin Type Description
EN / KEY Input Enables AT command mode
VCC Power 3.6–6V supply
GND Power Ground
TXD Output Serial data transmit
RXD Input Serial data receive (3.3V only)
STATE Output Connection status signal
🔌 Basic Wiring (Arduino Example)
HC-05 Arduino
VCC 5V
GND GND
TXD RX
RXD TX (via voltage divider)
EN optional (AT mode only)

⚠️ Important:
RXD is 3.3V logic only → use a 1k–2k resistor divider to avoid damage.