HC-05 Master Slave Bluetooth Module

Technical Specifications

• Supply voltage: 3.6 - 6 V
• Current consumed: maximum 30 mA
• I / O pins are compatible for 3.3 V (but in our tests it worked at 5 V)
• Communicates on the UART series
• Baudrate: 9600 - 460800 bps
• Transmission distance up to 10 m
• Transmission power: + 4 dBm
• Sensitivity reception: -80 dBm
• Dimensions: 35.7 x 15.2 mm

A very common example is the communication between the laptop and a robot from which you want to collect real-time data. For example, you can see how a line follower robot behaves as you go along the path and fix some problems.

The procedure to enter the AT mode is the following: 
- Feed the module 
- Press the small button (no need to hold the push), the LED should start to blink rapidly about 5 times per second 
- The module enters AT mode with baud rates of 9600 (which can be modified later)

Use with Arduino

In order to configure it with Arduino, the Arduino program is uploaded and the "Both NL & CR" serial number is set from the Arduino serial monitor.

The program uses the SoftwareSerial.h library to create a UART-based communication channel through the digital pins 2 and 3 (any digital pins can be used). Power up the module (supports power supply voltages between 3.6 V and 6 V) and go into AT mode (Module control module). You can communicate with the module via the serial monitor.

Here are some commands: 

• AT - check the connection - return OK 
• AT + ROLE = 1 - device e master = 0 - device e slave 
• AT + RESET - reset the device (will enter data) 
• AT + PSWD = the access password is changed (default: 1234) 
• AT + ADDR - returns the device address

To communicate with the Bluetooth module on your laptop (if it has this capability), use a serial communication program such as Putty, Terra Term or Real Term. They can be downloaded very easily and free of charge from the internet. To communicate with the Bluetooth module it must be in slave mode. Use your master device and send your 1234 password to your device (use the AT commands to find out this address - this will be in the format xxxx: x: xxxxxx).

There are numerous apps on Android (like S2 Terminal for Bluetooth), but also for other mobile operating systems. They offer graphical interfaces that make connection and communication very simple. To control a robot using these modules, you need to use laptop or phone Bluetooth or connect an identical module to your laptop with a USB-Serial converter such as the FTDI chip module.

The HC-05 card will read information from the laptop and send it to the robot that will retrieve the information and send it to Arduino and it will interpret the data and give the robot the necessary commands.