#include <avr/io.h>





void initUART(void) {
  // Formula for calculating baud
  // UBRR = (16000000 / (16 * 9600)) - 1
  uint16_t baudValue = 103; // round up value from calculation
  UBRR0H = (uint8_t)(baudValue >> 8); // 0
  UBRR0L = (uint8_t)baudValue; // 103

  UCSR0B = (1 << RXEN0) | (1 << TXEN0); // enable receive and transmit register
  UCSR0C = (1 << UCSZ01) | (1 << UCSZ00); // seting 8N1
}


unsigned char uartReceive(void) {
  while (!(UCSR0A & (1 << RXC0))) {}
  return UDR0; // get and return received data from buffer
}

unsigned char uartTransmit(unsigned char data) {
  while (!(UCSR0A & (1 << UDRE0))) {}
  UDR0 = data; // load data into buffer
  return data;
}


int main(void) {
  initUART();
  while (1) {
    // main loop
    unsigned char receivedData = uartReceive();
    uartTransmit(receivedData); // echo back received data
  }
}