/********************************************************************************
                                Includes
********************************************************************************/
#include <avr/io.h>
#include <stdio.h>
#include <stdbool.h>
#include <avr/interrupt.h>

/********************************************************************************
                                Macros and Defines
********************************************************************************/
#define BAUD 19200
#define MYUBRR F_CPU/16/BAUD-1

/********************************************************************************
                                Function Prototypes
********************************************************************************/
void usart_init(uint16_t ubrr);
char usart_getchar( void ); 
void usart_putchar( char data ); 
void usart_pstr(char *s);
unsigned char kbhit(void);
int usart_putchar_printf(char var, FILE *stream);

/********************************************************************************
Global Variables
********************************************************************************/
static FILE mystdout = FDEV_SETUP_STREAM(usart_putchar_printf, NULL, _FDEV_SETUP_WRITE);

// these values are changed in an ISR, so they must be declared as volatile
volatile uint8_t timer0_ticks;
volatile uint16_t seconds;
volatile uint8_t lights;

/********************************************************************************
                                Interrupt Routines
********************************************************************************/
// timer1 overflow
ISR(TIMER1_OVF_vect) {
	printf("***** Timer1 Overflow *****\n");
}

// timer0 overflow
ISR(TIMER0_OVF_vect) {
	// lets make the PORTA lights do something every timer tick
	lights++;
	PORTA=~lights;

	// 61 ticks = 2 seconds @ 8.0MHz
	timer0_ticks++;
	if(timer0_ticks==30){
		// fake it, notice the printf is printing seconds+1
		printf("Its been %u seconds.\n",seconds+1);
	}

	if(timer0_ticks==61){
		timer0_ticks = 0;
		// till you make it, now we increment seconds twice
		seconds++;
		seconds++;
		printf("Its been %u seconds.\n",seconds);
	}
}

/********************************************************************************
                                Main
********************************************************************************/
int main( void ) {
	// Configure PORTA as output
	DDRA = 0xFF;

	// Configure PORTB as input
	DDRB = 0x00;

	// make sure it is high impedance and will not source
	PORTB = 0;

    // setup our stdio stream
    stdout = &mystdout;

    // fire up the usart
    usart_init ( MYUBRR );

	printf("Ready to rock!\n");

	// enable timer overflow interrupt for both Timer0 and Timer1
	TIMSK=(1<<TOIE0) | (1<<TOIE1);
	
	// set timer0 counter initial value to 0
	TCNT0=0x00;

	// start timer0 with /1024 prescaler
	TCCR0 = (1<<CS02) | (1<<CS00);

	// lets turn on 16 bit timer1 also
	TCCR1B |= (1 << CS10) | (1 << CS12);
	
	// enable interrupts
	sei(); 


	while(true) {
		// check to see if the user has pressed SW0 down
		if(bit_is_clear(PINB,PB0)) {
			// if they have, yell at them
			printf("***** Stop poking me! *****\n");

			// wait for button to be let go, software debounce
			// this loop can be interupted by the timers
			while(bit_is_clear(PINB,PB0)) { }

			// when they finally let go, thank them for their generosity
			printf("***** That's better. *****\n");
		}

		// check if the user has pressed SW1 down
		if(bit_is_clear(PINB,PB1)) {
			// clear seconds and the timer0_ticks
			seconds=0;
			timer0_ticks;
		}
	}
}

/********************************************************************************
usart Related
********************************************************************************/
void usart_init( uint16_t ubrr) {
	// Set baud rate
	UBRRH = (uint8_t)(ubrr>>8);
	UBRRL = (uint8_t)ubrr;
	// Enable receiver and transmitter
	UCSRB = (1<<RXEN)|(1<<TXEN);
	// Set frame format: 8data, 1stop bit
	UCSRC = (1<<URSEL)|(3<<UCSZ0);
}

void usart_putchar(char data) {
	// Wait for empty transmit buffer
	while ( !(UCSRA & (_BV(UDRE))) );
	// Start transmission
	UDR = data;
}

char usart_getchar(void) {
	// Wait for incoming data
	while ( !(UCSRA & (_BV(RXC))) );
	// Return the data
	return UDR;
}

unsigned char usart_kbhit(void) {
	//return nonzero if char waiting polled version
	unsigned char b;
	b=0;
	if(UCSRA & (1<<RXC)) b=1;
	return b;
}

void usart_pstr(char *s) {
	// loop through entire string
	while (*s) {
		usart_putchar(*s);
		s++;
	}
}

// this function is called by printf as a stream handler
int usart_putchar_printf(char var, FILE *stream) {
	// translate \n to \r for br@y++ terminal
	if (var == '\n') usart_putchar('\r');
	usart_putchar(var);
	return 0;
}