Bluetooth is considered as the important wireless communication technic used in systems to transfer information between devices and HC-05 is an easy-to-use Bluetooth serial port protocol module.

HC-05 is a version2.0 Bluetooth module includes in the HC series Bluetooth module, it is easy to interface device which is been known as the prototype system, which are been mainly used at hobbyist projects and also at devices not having Bluetooth communication.

HC-05 Bluetooth module Specification & features

  • HC-05 is 0 enhanced data rate Bluetooth module
  • The maximum range of communication: <100m
  • Frequency range: 4GHz
  • Modulation: GFSK (Gaussian frequency-shift keying)
  • Supply voltage: +3.3v to 6.0v
  • Supply current: 30mA
  • Sensitivity: -80dBM at 0.1% BER
  • Emission power: ≤ 4dBm, class2
  • Speed: 3mbps at asynchronous communication & 1mbps at synchronous
  • Supported baud rate: 9600,19200,38400,57600,115200,230400,460800
  • Working temperature: -20 to +75°C
  • HC-05 Bluetooth follows the IEEE 802.15.1 standardized protocol
  • Serial communication is done with UART and TTL compatible protocol
  • Auto-connection function with last devices on power
  • Uses CSR Blue core 04-external single-chip Bluetooth system with CMOS technology.
  • Uses AFH (adaptive frequency hopping) feature
  • It has the ability to works as master/slave mode on a system.
  • Total size of the module: 26.9mm x 13mm x 2.2 mm



It is the PINOUT details of the whole HC-05 Bluetooth module 

Pin no: Pin name: Description
Pin01 Enable pin It is used to set data values at a high and low level
Pin02 VCC+ It is the positive supply provided (+5v)
Pin03 GND Ground
Pin04 TX Transmitter serial port
Pin05 RX Receiver serial port
Pin06 State It is used to indicate the module at ON/OFF state



In this category, we try to explain some of the important parts of the HC-05 Bluetooth module.

BC417 Bluetooth IC

It is a Bluetooth IC commonly used at Arduino compatible, they had 3.3v operating voltage and had a waveband range of 2.4GHz to 2.8GHz.

26MHz crystal oscillator

It is the most common crystal oscillator frequency range used at mobile phones and electronic circuits.

Flash memory IC

These types of flash memory IC had applications on mobile phones, digital cameras, etc…

Antenna trace on PCB

It is an onboard antenna trace on PCB, the antenna is embedded with a PCB board.

These types of antenna traces could handle a wide range of bandwidth, the thin film-like structure makes the antenna more compactable and weightless.



If you need the datasheet in pdf please click this link


The normal operation of an HC-05 Bluetooth module at system is to introduce a wireless communication two between devices, to transfer information, communicate with each other, and also to communicate with the board.

Bluetooth is a safer and efficient way to communicate between two systems, this is why applications based on Bluetooth are always there at almost all systems.

The natural operation of the HC-05 Bluetooth module is divided into two different modes,

  1. Data mode: Establish communication between two systems to communicate with each other and exchange data with each other.
  2. Command mode: on this mode, we actually can make changes to the HC-05 Bluetooth module.

Data mode

Data mode
Data mode

source: electronicwings

The figure will help you to understand the interfacing of the HC-05 Bluetooth module with a PC system and then establish a pathway to communicate with a smartphone.

This is just an example network circuit, for to make a Bluetooth wireless communication, you can use multiple systems to make communication between each other.

Command mode

Command mode
Command mode

This is how we need to make the connection between HC-05 Bluetooth and microcontrollers before getting into a command mode.

The command mode is used to made changes at the HC-05 Bluetooth module board, the change is like the change of passcode, baud rate, and name of the Bluetooth, etc.

The command mode is made by connecting the HC-05 Bluetooth module with serial to USB converter and PC.

The AT command is commonly used for making changes at the HC-05 module using the PC.

Uses of HC-05 Bluetooth module

  • We already know the HC-05 Bluetooth module is a prototypical board, so a project based on the Arduino board is the main application of the HC-05 module.
  • Using the HC-05 module, communication will happen between laptops, computers, and mobile phones.
  • Used to create communication between microcontrollers
  • Wireless robots and home automation

Projects based on HC-05 Bluetooth module

The projects based on the HC-05 Bluetooth module are always like Hobbyists projects, this is because the HC-05 module is a prototypical Bluetooth board.

  1. Arduino based model home automation project via HC-05 Bluetooth module

1. Arduino based model home automation project via HC-05 Bluetooth module
Arduino based model home automation project via HC-05 Bluetooth module

source: electronicwings

The shows the home automation connection diagram, the project consists of three major components relay board, Arduino-UNO board, and HC-05 Bluetooth module.

The circuit working operation is much simple, at first, we need to establish a connection between the Bluetooth module and a device, for example, a smartphone and then we can control the bulb or any home appliance using a smartphone.

  1. Android controlled robot car using HC-05 Bluetooth module

Android controlled robot car using HC-05 Bluetooth module
Android controlled robot car using HC-05 Bluetooth module

source: hobbyprojects

The figure shows the android controlled robot car project consists of an 89c2051 microcontroller, L293D motor controlling board, and HC-05 Bluetooth module.

The operation of this project is purely based on Bluetooth, we can use android devices to control the movement of the robot.

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