avr_init.cpp

#define BAUD 9600
#include <avr/io.h>
#include <util/delay.h>
#include <util/setbaud.h>
void uart_init(void) {
    UBRR0H = UBRRH_VALUE;
    UBRR0L = UBRRL_VALUE;

#if USE_2X
    UCSR0A |= _BV(U2X0);
#else
    UCSR0A &= ~(_BV(U2X0));
#endif

    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */
    UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */
}
void uart_putchar(char c) {
    loop_until_bit_is_set(UCSR0A, UDRE0); /* Wait until data register empty. */
    UDR0 = c;
}
int main(void)
{
  DDRB = 0x80; //Nakes PORTC as Output
  uart_init();
  while(1) //infinite loop
  {
    PORTB = 0x80; //Turns ON All LEDs
    _delay_ms(300); //1 second delay
    PORTB= 0x00; //Turns OFF All LEDs
    _delay_ms(100); //1 second delay
    uart_putchar('A');
  }
}
//https://appelsiini.net/2011/simple-usart-with-avr-libc/