HC-05 Bluetooth Module

Introduction

• It is used for many applications like wireless headsets, game controllers, wireless mouse, wireless keyboards, and many more consumer applications.
• It is IEEE 802.15.1 standardized protocol, through which one can build wireless Personal Area Network (PAN). It uses frequency-hopping spread spectrum (FHSS) radio technology to send data over air.
• It uses serial communication to communicate with devices. It communicates with a microcontroller using serial port (USART).

Specification

• Voltage: 3.6 V-6 V connected to the VCC pin
• Communication leads are working with voltage 3.3 V (tolerate 5 V)
• Current consumption: approx. 50 mA
• Class 2 – maximum transmitter power + 4 dBm
• Range: up to 10 m
• The password for pairing: 1234
• Standard: Bluetooth 2.0 + EDR
• The SPP profile with the possibility to configure via AT commands
• Communication: UART (RX, TX)
• Small dimensions: 39 x 16 mm

HC-05 Bluetooth Module Pin Diagram
Bluetooth serial modules allow all serial-enabled devices to communicate with each other using Bluetooth.

It has 6 pins:

1. Key/EN: It is used to bring Bluetooth module in AT commands mode. If Key/EN pin is set to high, then this module will work in command mode. Otherwise by default it is in data mode. The default baud rate of HC-05 in command mode is 38400bps and 9600 in data mode. HC-05 module has two modes:
   1. Data mode: Exchange of data between devices.
   2. Command mode: It uses AT commands which are used to change setting of HC-05. To send these commands to module serial (USART) port is used.
2. VCC: Connect 5 V or 3.3 V to this Pin.
3. GND: Ground Pin of module.
4. TXD: Transmit Serial data (wirelessly received data by Bluetooth module transmitted out serially on TXD pin)
5. RXD: Receive data serially (received data will be transmitted wirelessly by Bluetooth module).
6. State: It tells whether module is connected or not.