HC-05 Bluetooth Module

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Overview

HC-05 has a red LED on its board which shows the connection status of the board if the Bluetooth is connected. Before connecting the device to the HC-05 module this red LED blinks continuously periodically. And after connections, its blinking slows down. The module works on 3.3 V. One can also connect 5V supply voltage since the module has an onboard 5V regulator. The Bluetooth module has a 3.3 V level for TX and RX. The microcontroller can easily detect 3.3 V levels, Therefore, there is no need to shift transmit level of this Bluetooth module. However, we need to shift the transmit voltage level from the microcontroller to the RX of the module.

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To communicate the Bluetooth module with a smartphone, a smartphone requires a Bluetooth application for transmitting and receiving the data. One can find Bluetooth terminal applications for windows or android on the respective application store.

Working

The module immediately transmits all data received through the serial input over the air. When the module receives wireless data, it sends it out through the serial interface exactly as it was received. We need no user code specific to the Bluetooth module at all in the user microcontroller program.

Features and Specifications

Features

Works with Serial communication (USART) and TTL compatible
Follows IEEE 802.15.1 standardized protocol
Uses Frequency-Hopping Spread Spectrum (FHSS)
Can operate in Master, Slave, or Master/Slave mode
Can be easily interfaced with Laptop or Mobile phones with Bluetooth
Serial Bluetooth module for Arduino and other microcontrollers

Specifications

Bluetooth protocol: Bluetooth Specification v2.0+EDR
Frequency: 2.4GHz ISM band
Modulation: GFSK(Gaussian Frequency Shift Keying)
Emission power: ≤4dBm, Class 2
Sensitivity: ≤-84dBm at 0.1% BER
Speed: Asynchronous: 2.1Mbps(Max) / 160 kbps, Synchronous: 1Mbps/1Mbps
Security: Authentication and encryption
Profiles: Bluetooth serial port
Power supply: +3.3VDC 50mA
Working temperature: -20 ~ +75Centigrade
Dimension: 26.9mm x 13mm x 2.2 mm

Pinouts of HC-05

Pin Number	Pin Name	Description
1	Enable	This pin is used to toggle between Data Mode and AT command mode (set high). By default, it is in Data mode.
2	Vcc	Powers the module. Connect to +5V Supply voltage.
3	Ground	Ground pin of the module.
4	TX – Transmitter	Transmits Serial Data.
5	RX – Receiver	Receive Serial Data. It will broadcast every serial data given to this pin via Bluetooth.
6	State	It connected the state pin to the onboard LED, we can use it as feedback to check if Bluetooth works properly.

Applications of Bluetooth Module

Robotics

Robotic devices involve the operation or functions of Robots under the signals sent from a smartphone using an Android or smartphone Application and Bluetooth Communication. And, here Bluetooth module serves the purpose.

Home Automation

Making a wireless automation system, system requires a Bluetooth module for wireless communication with the electronic components. Hence, these systems employ Bluetooth modules for this purpose.