uscee459-lab4.c

/*************************************************************
*       at328-0.c - Demonstrate simple I/O functions of ATmega328
*
*       Program loops turning PC0 on and off as fast as possible.
*
* The program should generate code in the loop consisting of
*   LOOP:   SBI  PORTC,0        (2 cycles)
*           CBI  PORTC,0        (2 cycles)
*           RJMP LOOP           (2 cycles)
*
* PC0 will be low for 4 / XTAL freq
* PC0 will be high for 2 / XTAL freq
* A 9.8304MHz clock gives a loop period of about 600 nanoseconds.
*
* Revision History
* Date     Author      Description
* 09/14/12 A. Weber    Initial Release
* 11/18/13 A. Weber    Renamed for ATmega328P
*************************************************************/

#include <avr/io.h>
#include <stdio.h>
#include <util/delay.h>

void usart_init(unsigned short ubrr)
{
  UBRR0 = ubrr;
  UCSR0B |= (1 << TXEN0);
  UCSR0B |= (1 << RXEN0);
  UCSR0C = (3 << UCSZ00);
}

void usart_out(char ch)
{
  while ((UCSR0A & (1 << UDRE0)) == 0);
  UDR0 = ch;
}

char usart_in()
{
  while ( !(UCSR0A & (1 << RXC0)) );
  return UDR0;
}

void usart_outstring(char *s) {
  while (*s != '\0') {
    usart_out(*s);
    s++;
  }
}

int main(void)
{
  /* for 9600 baud on with 9.304MHz clock */
  usart_init(63);

  char buf[256];
  buf[0] = '\0';

  /*
  for (;;) {
    sprintf(&buf, "UCSR0A is %d\r\n", UCSR0A);
    usart_outstring(buf);
    sprintf(&buf, "RXC0 is %d\r\n", UCSR0A);
    usart_outstring(buf);
  }
  */

  /*
  for(;;) {
    char c = usart_in();
    usart_out(c);
  }
  */

  for (;;) {
    char c = usart_in();
    switch (c) {
      case 'a':
      case 'e':
      case 'i':
      case 'o':
      case 'u':
        sprintf(&buf, "You entered the vowel \"%c\"\r\n", c);
        usart_outstring(buf);
        break;
      default:
        sprintf(&buf, "You entered the consonant \"%c\"\r\n", c);
        usart_outstring(buf);
    }
  }
}