rtttl.c.txt

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>

// Music Data
#include "rtttl_data.h"

// Which pin is the speaker connected to?
#define SPEAKER_DDR		DDRB
#define SPEAKER_PORT		PORTB
#define SPEAKER			PB2

// Magic!
#define MAGIC_INDEX_PAUSE	63

// Initialize speaker pin as output
static void init_speaker(void) {
	SPEAKER_DDR |= (1<<SPEAKER);
}

// Activate speaker PWM
// alternatively, you can toggle the pin by yourself,
// but that is more cpu time consuming!
static void pwm_on(void) {
	// Deactivate Timer1 interrupts
	TIMSK1 = 0;

	// CTC mode
	TCCR1A |= (1<<COM1B1 | 1<<WGM11 | 1<<WGM10);

	// Prescaler 8
	TCCR1B = 1<<CS11 | 1<<WGM13 | 1<<WGM12;

	// Timer reset
	TCNT1 = 0;
}

// deactivate speaker pwm
static void pwm_off(void) {
	TCCR1A = 0;
	TCCR1B = 0;
}

// Play melody num
static void music(uint8_t num) {
	
	uint8_t curDuration = 0;
	
	// Read jump target for array
	uint16_t i = pgm_read_word(&(melody_targets[num]));

	// first byte of each melody is the default duration
	uint8_t defaultDuration = pgm_read_byte(&(melodies[i]));
	i++;

	// second byte of each melody is the default bpm
	uint8_t defaultBPM = pgm_read_byte(&(melodies[i]));
	i++;

	while(pgm_read_byte(&(melodies[i])) != 0x00 && pgm_read_byte(&(melodies[i+1])) != 0x00) {

		uint16_t dauer_ms;

		// if last bit is set, next byte is customDuration byte
		if(pgm_read_byte(&(melodies[i])) & 0x01) {
			curDuration = pgm_read_byte(&(melodies[i+1]));
		} else {
			curDuration = defaultDuration;
		}

		// REPLACE THIS WITH FLOATING POINT IF PROGRAM DOESNT WORK	
		dauer_ms = (((60000 / defaultBPM) * defaultDuration) / curDuration);

		// note is dotted if second bit is set
		if(pgm_read_byte(&(melodies[i])) & 0x02) {
			dauer_ms = dauer_ms + (dauer_ms / 2);
		}

		// array index (first 6 bit) and duration
		// if index is 63 (MAGIC_INDEX_PAUSE) then the note is a pause
		if(pgm_read_byte(&(melodies[i])) / 4 != MAGIC_INDEX_PAUSE) {
	
			uint16_t halbe_periodendauer_us = pgm_read_word(&(halbe_periodendauern[pgm_read_byte(&(melodies[i])) / 4]));

			// IF YOU DO NOT NEED HIGH PERFORMANCE, THIS
			// PWM PART CAN BE REPLACED BY MANUAL TOGGLING
			// THE SPEAKER PIN!

			pwm_on();
			
			// ratio of OCR1A and OCR1B is duty cycle of PWM
			// can be used for "pitching"
			OCR1A = 2 * (halbe_periodendauer_us * 2) / 3;
			OCR1A = 2 * halbe_periodendauer_us;
			OCR1B = halbe_periodendauer_us;

			// THIS PART WAITS "dauer_ms" MILLISECONDS USING A TIMER
			// CAN BE REPLACED WITH A BUSY LOOP USING "_delay_ms"
			clock = 0;
			while(clock < dauer_ms);

			pwm_off();

		} else {
			pwm_off();

			clock = 0;
			while(clock < dauer_ms);
		}

		// if there is a custom duration byte, next note is in the byte after that
		if(pgm_read_byte(&(melodies[i])) & 0x01) {
			i++;
		}

		i++;

	}
}
//]]

int main(void) {

	// ...
	
	init_speaker();

	// ...

	while(1) {

		for(i=0; i<MELODIES; i++) {
			music(i);
		}

	}

	return 0;
}