HC-05 Bluetooth Module

HC-05 Bluetooth Module (Master/Slave) - Wireless Serial Port Bridge

The HC-05 Bluetooth Module is a highly popular and affordable solution for adding bidirectional wireless communication to electronics projects, effectively serving as a wireless serial cable replacement. This module is based on the CSR Bluecore 04-External chip and complies with the Bluetooth v2.0+EDR specification.

Its primary function is establishing a Serial Port Protocol (SPP) connection, allowing transparent, full-duplex data transfer between a microcontroller (like an Arduino) and devices such as smartphones, laptops, or other HC−05 modules. Unlike the slave-only HC−06, the HC−05 can be configured as both a Master (initiates connections) and a Slave (accepts connections) using AT Commands while in Command Mode (KEY/EN pin HIGH). Although the board accepts a 5V power supply due to its onboard regulator, its logic levels are 3.3V, requiring a voltage divider on the RXD pin when interfacing with 5V microcontrollers to prevent damage.

🔧 Key Features  

• Bluetooth Version: v2.0+EDR (Enhanced Data Rate).
   
• Role: Configurable as Master, Slave, or Slave−Loop.
   
• Interface: UART (TX/RX) Serial communication.
   
• Operating Frequency: 2.4 GHz ISM Band.
   
• Security: Authentication and Encryption (PIN code: "1234" default).
 
• Control Mode: Dedicated KEY/EN pin to enter AT Command Mode (38400 bps).
 

💡 Applications

• Wireless Control of RC vehicles and robotics.
   
• Home Automation (e.g., controlling lights or devices via smartphone).
 
• Data logging and real-time monitoring from sensors to a PC/App.
 
• Creating wireless links between two microcontrollers.
 

⚙️ Technical Specifications Summary

📦 Package Includes   

• 1 × HC−05 Bluetooth Module (with baseboard)