HC-05 Bluetooth Module

HC-05 is a Bluetooth device used for wireless communication. It works on serial communication (UART).

• It is a 6-pin module.
• The device can be used in 2 modes; data mode and command mode.
• The data mode is used for data transfer between devices whereas the command mode is used for changing the settings of the Bluetooth module.
• AT commands are required in command mode.
• The module works on 5V or 3.3V. It has an onboard 5V to 3.3V regulator.
• As the HC-05 Bluetooth module has a 3.3 V level for RX/TX and the microcontroller can detect 3.3 V level, so, no need to shift the transmit level of the HC-05 module. But we need to shift the transmit voltage level from the microcontroller to RX of the HC-05 module.

For more information about the HC-05 Bluetooth module and how to use it, refer to the topic Bluetooth module HC-05 in the sensors and modules section.

For information on UART in 8051 and how to use it, refer to the topic on UART in 8051 in the 8051 inside section.

HC-05 Bluetooth Connection with 8051

Example

Here let’s develop a small application in which we can control LED ON-OFF through smartphones.

This is done by interfacing 8051 with the HC-05 Bluetooth module. Data from HC-05 is received/ transmitted serially by 8051.

In this application when 1 is sent from the smartphone, LED will turn ON and if 2 is sent LED will get Turned OFF. If received data is other than 1 or 2, it will return a message to mobile that select the proper option.

HC-05 8051 Programmig  

1. Initialize 8051 UART communication.
2. Receive data from the HC-05 Bluetooth module.
3. Check whether it is ‘1’ or ‘2’ and take respective controlling action on the LED.

/*
 *HC-05 Bluetooth interfacing with 8051 to control LED via smartphone
 *http://www.electronicwings.com
 */

#include <reg51.h>
#include "UART_H_file.h"	/* Include UART library */

sbit LED=P1^0;

void main()
{
	char Data_in;
	UART_Init();		/* Initialize UART */
	P1 = 0;			/* Clear port initially */
	LED = 0;		/* Initially LED turn OFF */
	while(1)
	{
		Data_in = UART_RxChar();  /* Receive char serially */
		if(Data_in == '1')
		{
			LED = 1;/* Turn ON LED */
			UART_SendString("LED_ON");  /* Send status of LED*/
		}
		else if(Data_in == '2')
		{
			LED = 0;/* Turn OFF LED */
			UART_SendString("LED_OFF");  /* Send status of LED*/
		
		}
		else
			UART_SendString("Select proper option");
	
	}
}

Video Of LED Control using HC-05 Bluetooth and 8051