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 Programming
Initialize 8051 UART communication.
Receive data from the HC-05 Bluetooth module.
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");
}
}
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