Bluetooth Module HC-05

Bluetooth Module

The HC-05 Bluetooth Module supports both data mode for seamless communication and command mode for configuration via AT commands.

Ideal for connecting microcontrollers, smartphones, and other Bluetooth-enabled devices, this module is a popular choice for hobbyists, educators, and professionals alike.

Features

• Bluetooth 2.0 + EDR compliant
• Master and slave mode support
• UART interface for easy integration with microcontrollers
• Range up to 10 meters
• Low power consumption (approximately 50mA)
• Configurable via AT commands for custom settings
• LED indicator for connection status
• Supports SPP (Serial Port Protocol) for serial communication (with the possibility to configure via AT commands)
• Operates in data mode (default 9600bps) and command mode (38400bps)

Specifications

• Voltage: 3.6V to 6V (VCC pin)
• Communication Leads: 3.3V (tolerates 5V), can be directly connected to 5V microcontrollers
• Current Consumption: Approximately 50mA
• Bluetooth Class: Class 2, maximum transmitter power: +4dBm
• Standard: Bluetooth 2.0 + EDR
• Communication: UART (RX, TX)
• Dimensions: Approximately 39mm x 16mm (breakout board)
• Operating Temperature: -20°C to +75°C
• Default Baud Rate: 9600bps (data mode), 38400bps (command mode)
• Default Pairing Password: 1234 or 0000

Pin Description

The HC-05 module typically comes with the following pins on its breakout board:

• VCC: Power supply pin. Connect to a voltage source between 3.6V and 6V
• GND: Ground pin. Connect to the ground of your circuit.
• TXD: Transmit data pin. Connect to the RX pin of your microcontroller for serial communication.
• RXD: Receive data pin. Connect to the TX pin of your microcontroller.
• STATE: Indicates the connection status. It is high (3.3V) when the module is connected to another device and low when not connected.
• EN (or KEY): Enable pin. Pull this pin high (connect to VCC) before powering on the module to enter AT command mode for configuration. Leave it disconnected or low for normal data mode.

Overview of Working Modes

The HC-05 Bluetooth module operates in two primary modes:

1. Data Mode: Used for transmitting and receiving data over Bluetooth.
2. Command Mode: Used for configuring the module’s settings via AT commands.

Below is a detailed comparison based on several key features :

Data Mode :

• Purpose: Transmit and receive serial data over Bluetooth.
• Baud Rate: Configurable, with a default setting of 9600bps.
• How to Enter: Default mode when the EN/KEY pin is low or disconnected.
• LED Behavior: Rapid blink when not connected or Slow blink when connected.
• Bluetooth Activity: Active—sends and receives data over Bluetooth.

Command Mode :

• Purpose: Configure the module using AT commands (e.g., set name, baud rate, or role).
• Baud Rate: 38400bps if entered by pulling EN/KEY high before power-on.
• Uses the current configured baud rate if entered during operation.
• How to Enter: Pull the EN/KEY pin high (either before power-on or while powered on).
• LED Behavior: Slow blink (e.g., once every two seconds).
• Bluetooth Activity: Inactive—only accepts AT commands via the serial interface, with no Bluetooth communication.

Applications

• Wireless communication between microcontrollers (e.g., Arduino, PIC, ESP32)
• Connecting to smartphones or computers for data transfer and control
• Home automation projects, such as controlling lights or appliances
• Robotics and remote control systems
• IoT devices for wireless data logging and monitoring
• Popular in educational and hobbyist projects for learning wireless communication

Documentation :

• Documentation of the module HC-05
• Example of connection with Raspberry Pi