Bluetooth HC-05 Interfacing With Microcontroller

HC-05 is a Bluetooth module that is mostly use in Embedded Electronics for the purpose of transfer serial data wirelessly to a Android, Laptop and also Microcontroller to Microcontroller. So we can say Bluetooth is a wireless replacement of Serial Communication. HC-05 Module (fig. 1) have 6-pin. 

Front View of HC-05

Back View of HC-05

fig. 1

Pin Description:

1. State  - State pin is high if device is connected to another device  
2. RxD  - Receiver Pin of Bluetooth (max 3.3V)
3. TxD  - Transmitter pin of Bluetooth
4. GND - Ground Supply
5. Vcc   - +5V Supply
6. EN    - This pin is use to change mode(AT Command, Communication                       mode)

Note.  Basically HC-05 work at 3.3 V  but there is no problem to use this module at 5V. But the Tx &            Rx pin are at 3.3V level. so DON'T CONNECT Tx Rx pin Directly to Microcontroller Drive at 5V. So use a voltage divider to convert 5V in to 3.3V level. (fig.2)

Fig.2 Voltage Divider Circuit use to convert Voltage level

   

here we can also use resistance of same value. 

Communication Mode:-  Communication using HC-05 is very easy. connect HC-05 with MCU as shown in fig.3. Bluetooth is turn on then check bluetooth device in your Laptop/ Android. then pair this bluetooth with Laptop/ Android. if u use android download "Blue Term " android application from google play. open this bluetooth in application. than send "Hello World" from Microcontroller serial. and u receive in your in application. 

fig.3 connection