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AVR | USART Home Automation

In this tutorial, we will learn about the Universal Synchronous and Asynchronous Serial Receiver and Transmitter (USART) Home Automation. By Suryaveer Singh Last updated : May 12, 2023

Features of USART

The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a highly flexible serial communication device. The main features are:

• Full Duplex Operation (Independent Serial Receive and Transmit Registers)
• Asynchronous or Synchronous Operation
• Master or Slave Clocked Synchronous Operation
• High-Resolution Baud Rate Generator
• Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits
• Odd or Even Parity Generation and Parity Check Supported by Hardware
• Data Overrun Detection
• Framing Error Detection
• Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter
• Three Separate Interrupts on TX Complete, TX Data Register Empty, and RX Complete
• Multi-processor Communication Mode
• Double Speed Asynchronous Communication Mode

These are some of the features of USART, we would now lean to create a program in which we would use Bluetooth technology to open and close a LED bulb. In our program, we would take a variable X, such that if X=A our bulb will glow and if X=B the bulb will stop glowing.

AVR | USART Home Automation: Example

In the similar we can also use a fan instead of LED, then we would be controlling our Fan to start or stop.

Program

#include <avr/io.h>

void usart_string(char*);

int main(void)
{
	char x;
	DDRA = 0x01;
	UBRRL= 51;
	UCSRB= 0x18;
	UCSRC= 0x86;

	usart_string("Sam");

	while(1)
	{
		while((UCSRA&(1<<RXC))==0);
		x=UDR;
		if(x=='A')
		{
			PORTA=0x01;
		}
		else if(x=='B')
		{
			PORTA=0x00;
		}		
	}
}

void usart_string(char*p)
{
	while(*p!='\0')
	{
		UDR=*p;
		while((UCSRA&(1<<TXC))==0);
		UCSRA|=1<<TXC;
		p++;
	}
}

Explanation

• Write all the header files as written above.
• Take a variable X which will decide whether our bulb will be ON or OFF.
• DDRA=0x01 indicates that the Led bulb is connected.
• UBRRL=51; indicates that the baud rate is set to 9600.
• UCSRB=0x18 means R_x and T_x are enabled.
• The usart_string will print the word written inside it.
• Inside the while loop, we have written our bulb glowing condition such that when A is received the LED will glow and when B is received the LED bulb will stop glowing.

BAUD RATE

It is the rate at which the information is processed/transferred to the communication channel.

Calculation of BAUD RATE

Where, fOSC is "System Oscillator Clock Frequency".

Simulation

Simulation Explanation

• Select the following components:
  1. Atmega16
  2. LED Red
  3. From virtual instruments mode select a VIRTUAL TERMINAL
• Add the components as shown in the figure.
• Double click on ATmega16 and make its speed as 8000000 and upload the hex file in it.
• When we will start the simulation a screen will appear that would be our simulation for a Bluetooth screen.
• Typing A will glow the bulb and typing B will stop the bulb from glowing.

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