ATmega328_USART_test.c

#include <avr/io.h>
#include <util/delay.h>
#define BAUD 9600
#include <util/setbaud.h>

#define BLINK_DELAY_MS 1000

void initUSART(void) {                                /* requires BAUD */
  UBRR0H = UBRRH_VALUE;                        /* defined in setbaud.h */
  UBRR0L = UBRRL_VALUE;
#if USE_2X
  UCSR0A |= (1 << U2X0);
#else
  UCSR0A &= ~(1 << U2X0);
#endif
  /* Enable USART transmitter/receiver */
  UCSR0B = (1 << TXEN0) | (1 << RXEN0);
  UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);   /* 8 data bits, 1 stop bit */
}

void transmitByte(uint8_t data) {
  /* Wait for empty transmit buffer */
  loop_until_bit_is_set(UCSR0A, UDRE0);
  UDR0 = data;                                            /* send data */
}

uint8_t receiveByte(void) {
  loop_until_bit_is_set(UCSR0A, RXC0);       /* Wait for incoming data */
  return UDR0;                                /* return register value */
}


/* Here are a bunch of useful printing commands */

void printString(const char myString[]) {
  uint8_t i = 0;
  while (myString[i]) {
    transmitByte(myString[i]);
    i++;
  }
}


int main (void)
{
  /* set pin 5 of PORTB for output*/
  DDRB |= _BV(DDB5);
  initUSART();

  while (1) {
    /* set pin 5 high to turn led on */
    PORTB |= _BV(PORTB5);
    _delay_ms(BLINK_DELAY_MS);

    /* set pin 5 low to turn led off */
    PORTB &= ~_BV(PORTB5);
    _delay_ms(BLINK_DELAY_MS);


    //transmitByte(0x41);
    printString("Hi\n");
  }
}