Final code.

Could add some comments

lab_2/main.c

@@ -7,22 +7,13 @@
 
 #include "main.h"
 
-uint8_t play_flag = 0;
-uint8_t button_flag = 0;
-
-ISR(INT0_vect) {
-	// Disable interrupts
-	cli();
-
-	// Notify of button press
-	button_flag = 1;
-}
+bool play_flag = 0;
 
 /*
  * Pin Definitions:
  * PB2 -> OC0A output
  * PB3 -> OC1A output
- * PB0 -> Switch Input
+ * PD2 -> Switch Input
  */
 void gpio_init() {
 	// Piezo Out
@@ -31,13 +22,6 @@ void gpio_init() {
 	// Switch Input Setup
 	DDRD &= ~(1 << DDD2);
 	PORTD |= (1 << PORTD2);
-	
-	// Configure Interrupt Stuff
-	// Set falling edge for INT0
-	MCUCR |= (1 << ISC01) | (0 << ISC00);
-	
-	// Enable INT0
-	GIMSK |= (1 << INT0);
 }
 
 void timer_init( ) {
@@ -53,7 +37,9 @@ void timer_init( ) {
 	TCCR1B = (1 << WGM12);
 }
 
-void play_beat() {
+
+// Returns true for a "successful" note, false for end of song.
+bool play_beat() {
 	static uint8_t duration_left[2] = {0};
     static uint16_t song_location[2] = {0};
 		
@@ -61,6 +47,7 @@ void play_beat() {
 	if (song_location[0] == SPEAKER0_LEN) {
 		song_location[0] = 0;
 		song_location[1] = 0;
+		return false;
 	}
 	
 	// Set note
@@ -112,40 +99,38 @@ void play_beat() {
 	}
 	_delay_ms(BEAT_LENGTH * REST_FRACTION);
 	
+	return true;
 }
 
 int main(void)
 {
 	gpio_init();
 	timer_init();
-	
-	sei();
-	
-    /* Replace with your application code */
+
+	beat_t beat = {
+		.note = a,
+		.duration = 20,
+		.octave = 0,
+	};
+	play_note(beat, 1);
+
     while (1) 
     {
-		if (play_flag) {
-			play_beat();
-		}
-		
-		if (button_flag) {
-			button_flag = 0;
+
+		if (bit_is_clear(PIND, PIND2)) {
+			// Play song until the end
+			while(play_beat());
 			
+			// Turn off speakers once song is over
 			beat_t beat = {
 				.note = rest,
+				.duration = 0,
+				.octave = 0, // octave doesn't matter, its a rest
 			};
 			play_note(beat, 0);
 			play_note(beat, 1);
-			_delay_ms(100);
-			sei();
 		}
 		
-		if ( bit_is_clear(PIND, PIND2) &&  (play_flag == 0)) {
-			cli();
-			play_flag = 1;
-			_delay_ms(100);
-			sei();
-		}
 		
     }
 }

lab_2/main.h

@@ -8,17 +8,24 @@
 #include <avr/pgmspace.h>
 #include <util/delay.h>
 
-#include "notes.h"
+#include <stdbool.h>
+
 
 #define TEMPO			(120 * 4)		// Tempo of song (bpm)
 #define REST_FRACTION	0.3				// Fraction of the beat to stay silent between notes
 #define BEAT_LENGTH		60000 / TEMPO	// Length of each note (ms)
 
 
+// Song Selection
+#define CRAB_RAVE
+
 #define OCTAVES				2
 #define NOTES_PER_OCTAVE	12
+
+#ifdef CRAB_RAVE
 #define SPEAKER0_LEN		38
 #define SPEAKER1_LEN		96
+#endif
 
 typedef enum {
 	a = 0, b, c, d, e, f, g,

lab_2/song.c

@@ -1,5 +1,7 @@
 #include "main.h"
 
+#ifdef CRAB_RAVE
+
 const beat_t PROGMEM song_speaker0[SPEAKER0_LEN] = {
 	{.note = g, .duration = 4, .octave = 0 },
 	{.note = g, .duration = 4, .octave = 0 },
@@ -139,3 +141,5 @@ const beat_t PROGMEM song_speaker1[SPEAKER1_LEN] = {
 	{.note = f, .duration = 1, .octave = 1 },
 	{.note = e, .duration = 1, .octave = 1},
 };
+
+#endif