Interfacing HC-05 Bluetooth module with AVR Microcontroller Using Atmega

Step 4. Click on Ports. In our project, we will be using Port C4 and C5 for led interfacing. So, make Bit 4 and bit 5 as output by clicking on it. As shown below:

Step 5. We will use USART for Rx and Tx. So, click on USART option and click on Receiver option and leave rest as it is.

Step 6. Click on Program -> Generate, Save and Exit. Now, more than half of our work is completed

Step 7. Make a New folder on desktop so, that our files remains in folder otherwise it we will be scattered on whole desktop window. Name your folder as you want and I suggest use the same name to save program files.

We will be having three dialogues box one after other to save files.

Do the same with other two dialogue boxes which will appear after you save the first.

Now, your workspace looking like this.

Our most of the work is completed with the help of the Wizard. Now, we have to write only few lines of code to interface the bluetooth module and control the LED.

Circuit Diagram:

Circuit diagram for interfacing Bluetooth HC-05 with AVR is given below.

Hookup the one side of FRC cable to USBASP programmer and other side will connect to SPI pins of microcontroller as described below:

1. Pin1 of FRC female connector -> Pin 17 ,MOSI of Atmega8
2. Pin 2  connected to Vcc of atmega8 i.e. Pin 7
3. Pin 5 connected to Reset of atmega8 i.e. Pin 1
4. Pin 7 connected to SCK of atmega8 i.e. Pin 19
5. Pin 9 connected to MISO of atmega8 i.e. Pin 18
6. Pin 8 connected to GND of atmega8 i.e. Pin 8

Connect the remaining components on the breadboard as per circuit diagram.

Code and Explanation:

Complete AVR code with Demonstration Video is given at the end of the article.

Here we have declared a variable in void main function for storing incoming character from Bluetooth module.

#include <io.h>
// Declare your global variables here
// Standard Input/Output functions
#include <stdio.h>
void main(void)
{
char var;                 // Declare your local variables here

Rest of the code is easy and can be easily understandable. Now, come on the last lines of code where you will find a while loop. Our main code will be in this loop. Here we are continuously checking the incoming character from the Bluetooth module and turning the LED On or off accordingly.

while (1)
      {
       scanf("%c",&var);                    //this function is to used to check any character coming from our android app .                    
      if (var == 'a')                              // We will send ‘a’ from Bluetooth Terminal to ON the LED and ‘b’ to OFF the LED
      {
            PORTC.5 = 1;
            PORTC.4 = 0;
      }      
          if (var == 'b')
      {
            PORTC.5 = 0;
            PORTC.4 = 0;
      }     
      }

Our code is completed. Now, we have to build our project. Click on Build the project icon as shown.

After building the project, a HEX file is generated in the Debug-> Exe folder which can be found in the folder you make previously to save your project. We will use this HEX file to upload in atmega8 using Sinaprog software.

Uploading the code to Atmega 8 using Sinaprog:

We will upload the above generated Hex file using the Sinaprog, so open it and Choose Atmega8 from Device drop down menu. Select the HEX file from the Debug-> Exe folder as shown.

Now, Click on Program.

Your Microcontroller is programmed. Now, we need an Android app to connect with our module. We will use “Bluetooth Terminal app” to control the LED light.  

Android App for controlling LED using AVR:

We will use “Bluetooth Terminal app” in our smart phone to talk to the HC-05 at the other end to control the LED light.  This app can be downloaded from given link:

https://play.google.com/store/apps/details?id=Qwerty.BluetoothTerminal&hl=en_IN

You can power up your circuit using the same usbasp by plugging it into your PC or you can apply external 5V (not more than 5!!!!!) to the Atmega8 Vcc pin.

After installing it .Open the app and connect it with Bluetooth module (HC-05 and default password is 1234).

Now, send ‘a’ and see the led will glow. Send ‘b’, led will off.

So now by sending the character ‘a’ and ‘b’, you can control the LED wirelessly using your Smartphone. And if you use the voice keyboard with Bluetooth app then you don’t even need to type the character ‘a’ and ‘b’, you can just speak them and can control the LED using your voice.