atmega328p-uartbasic.c

#define F_CPU 16000000UL
 
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdlib.h>
#include <stdio.h>
#include <util/delay.h>
 
#define BAUD 9600 // define baud
#define BAUDRATE ((F_CPU)/(BAUD*16UL)-1) // set baud rate value for UBRR
 
// function to initialize UART
void uart_init (void)
{
    UBRR0H = (BAUDRATE>>8); // shift the register right by 8 bits
    UBRR0L = BAUDRATE; // set baud rate
    UCSR0B|= (1<<TXEN0)|(1<<RXEN0); // enable receiver and transmitter
    UCSR0C = (3<<UCSZ00);
}
 
int uart_transmit(char data  )
{
    while (!( UCSR0A & (1<<UDRE0))); // wait while register is free
    UDR0 = data; // load data in the register
    return 0;
}
 
unsigned char uart_receive( void )
{
    while ( !(UCSR0A & (1<<RXC0)) );
    return UDR0;
}
 
 
int main(void)
{
    uart_init();
    FILE mystdio = FDEV_SETUP_STREAM(uart_transmit, uart_receive, _FDEV_SETUP_RW);
     
    stdout = &mystdio;
    stdin = &mystdio;
    char lol[5];
     
    while (1)
    {
        printf("Hello World\n\r");
        fgets(lol,5,stdin);
        _delay_ms(1000);
    }
}