/* 
Play music with your robot!

Buzzer example for the Orangutan/ATmega168. 

This example uses Timer2 in "Clear Timer/Counter on Compare Match" mode to generate the buzzer frequency.
The counter is incremented at 125 kHz, and resets when count = OCR2A. Upon reset, buzzer port pin is toggled.

The longest period before overflow (when OCR2A=255) corresponds to 488 Hz or buzzer frequency=244 Hz. 
Higher frequencies are set by reducing the value of OCR2A.

In this example, notes are defined according to the equal interval twelve tone scale.

CPU clock frequency assumed to be 8 MHz. If different, TCCR2 divider should be changed appropriately.

Produces about 1312 bytes of loaded code with -O3
sjames_remington at yahoo dot com
*/

#define F_CPU 8000000UL 
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

// TIMER 2 Interrupt service vector
// This routine is called with TIMER2 count (TCNT2) = OCR2A, which is set on the fly
// Operation is to simply toggle the buzzer line
//

ISR(TIMER2_COMPA_vect)
{
PORTB ^= 1;					//toggle buzzer output line
}

/*
Set up buzzer to play tones. Timer/Counter 2 is used in CTC mode, clear timer on compare/match
Clocked at 125 kHz,  = 8MHz/64  
OCR2A  overflow  buzzer
value    freq    freq
255      488     244    ("concert A" = 440 Hz)
128      976     488
64      1953     976
32      3906    1953

For other clock ratios, multiply or divide accordingly

Individual notes are = base frequency*2^(1/12), on twelve tone scale (1.05946 multiplicative factor)
Here, we define notes by the value of OCR2A:

A0  255 A2 63 A3 31
A#  241    67    33
B   227    71    35
C   214    75    37
C#  202    80    40
D   191    85    42
D#  180    90    44
E   170    95    47
F   161   101    50
F#  152   107    53
G   143   113    56
G#  135   120    59
A1  127   127 A2 63
*/       

/* 
define three octaves of notes for coding convenience. x=sharp
*/

#define p   0   //pause, no sound
#define a0  255
#define ax0 241
#define b0  227
#define c0  214
#define cx0 202
#define d0  191
#define dx0 180
#define e0  170
#define f0  161
#define fx0 152
#define g0  143
#define gx0 135
#define a1  127
#define ax1 120
#define b1  113
#define c1  107
#define cx1 101
#define d1  95
#define dx1 90
#define e1  85
#define f1  80
#define fx1 75
#define g1  71
#define gx1 67
#define a2  63
#define ax2 59
#define b2  56
#define c2  53
#define cx2 50
#define d2  47
#define dx2 44
#define e2  42
#define f2  40
#define fx2 37
#define g2  35
#define gx2 33
#define a3  31

void init_buzzer(void)
{
	DDRB |= 1;				//set data direction reg bit 0 to output
	PORTB &=~(1);			//set buzzer output low
	TCCR2A= (1<<WGM21);	//mode 2, clear timer on compare match
	TCCR2B=4;				//CS22=1,CS21=0,CS20=0	=> counter increments at 8 MHz/64 = 125 kHz, 
							// ... Counter overflows at 125kHz/256 = 488 Hz => lowest buzzer freq = 244 Hz
	TCNT2=0;				//clear counter
	OCR2A=255;				//set both compare match registers to MAX
	OCR2B=255;				//set both compare match registers to MAX
	TIMSK2=(1<<OCIE2A);	//enable interrupt on compare match with OCR2A
}

	
int main(void)
{
	int i,j;
	double delay;
	unsigned char note,dur;
/*
tune array "Fuer Elise" stolen from AVR Butterfly code example. Thanks, ATMEL Norway! 
Tune array entries are byte pairs: [duration (8=whole note, etc.), note (or p=pause=0)]
duration=0 ends the tune
The final byte is intended to be the repeat flag, but this feature has not been implemented
*/
	unsigned char tune[]=		//Fuer Elise, with apologies
	        {
            8,e1, 8,dx1, 8,e1, 8,dx1, 8,e1, 8,b0, 8,d1, 8,c1, 4,a0, 8,p, 
            8,c0, 8,e0, 8,a0, 4,b0, 8,p, 8,e0, 8,gx0, 8,b0, 4,c1, 8,p, 8,e0, 
            8,e1, 8,dx1, 8,e1, 8,dx1, 8,e1, 8,b0, 8,d1, 8,c1, 4,a0, 8,p, 8,c0, 
            8,e0, 8,a0, 4,b0, 8,p, 8,e0, 8,c1, 8,b0, 4,a0, 
			8,p,8,p,  //up one octave for test!
            8,e2, 8,dx2, 8,e2, 8,dx2, 8,e2, 8,b1, 8,d2, 8,c2, 4,a1, 8,p, 
            8,c1, 8,e1, 8,a1, 4,b1, 8,p, 8,e1, 8,gx1, 8,b1, 4,c2, 8,p, 8,e1, 
            8,e2, 8,dx2, 8,e2, 8,dx2, 8,e2, 8,b1, 8,d2, 8,c2, 4,a1, 8,p, 8,c1, 
            8,e1, 8,a1, 4,b1, 8,p, 8,e1, 8,c2, 8,b1, 4,a1, 
            0, 1
			};
	init_buzzer();
	DDRB &= ~(1);			//turn off buzzer for now by setting PORTB.0 = input
	
	i=0;
	sei();
	do {
		dur=tune[i++];
		delay = (double) (dur * 32);  //increase note duration by maximum constant factor (dur=8 max!)
		note=tune[i++];
		if (note) {
		OCR2A=note;		//set OCR2A for compare match
		DDRB |=1;		//turn on buzzer
		}
		else DDRB &=~(1);	// silence for this period
		for (j=1; j<8; j++) _delay_ms(delay);  //delay=262. max ~ 1/4 second. The "8" was chosen to sound OK
		}
	while (dur>0);
   return 0;
}