audio.c

//Integer approximations to frequencies for music notes covering the 2 octaves around middle C
#define B4 494
#define B4F 466
#define A4S 466
#define A4 440
#define A4F 415
#define G4S 415
#define G4 392
#define G4F 370
#define F4S 370
#define F4 349
#define E4 330
#define E4F 311
#define D4S 311
#define D4 294
#define D4F 277
#define C4S 277
#define C4 262 //Middle C
#define B3 247
#define B3F 233
#define A3S 233
#define A3 220
#define A3F 208
#define G3S 208
#define G3 196
#define G3F 185
#define F3S 185
#define F3 175
#define E3 165
#define E3F 156
#define D3S 156
#define D3 147
#define D3F 139
#define C3S 139
#define C3 131

#define SEMIBREVE 1.0
#define MINIM 1.0/2
#define CROTCHET 1.0/4
#define QUAVER 1.0/8
#define SEMIQUAVER 1.0/16

#define VOL_HIGH 3
#define VOL_MED 2
#define VOL_LOW 1

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

#include <math.h>

void setVolume(int volume);
void setBPM(int bpm);
void note(int freq, float beats);
void tone(int freq, long cycles);
void pulse(void);
float dot(float beats, int dots);
void n_on(void);
void n_off(void);


int audio_bpm = 100;
int audio_volume = VOL_LOW;

void setVolume(int volume){
	audio_volume = volume;
}
void setBPM(int bpm){
	audio_bpm = bpm;
}

void note(int freq, float beats){
    float bps = (audio_bpm/60.0);//beats per second
    float sec = bps * beats;//seconds
    long cycles = freq * sec;
    tone(freq, cycles);
}

void tone(int freq, long cycles){
    
    long period = 1000000/freq;
    long rest = period - (10*audio_volume);
    for(;cycles;cycles--){
        //high portion of wave
        long pulses;
        for(pulses = audio_volume; pulses; pulses--){
            pulse();
        }
        //low portion
        long delays;
        for(delays = rest/5; delays; delays--){
            _delay_us(5);
        }
    }

}

void pulse(){
    //output low
    n_on();
    _delay_us(5);
    //output high
    n_off();
    _delay_us(5);
}

void n_on(){
    DDRD |=  _BV(PD7); PORTD &= ~_BV(PD7);//output low
    DDRD |=  _BV(PD5); PORTD &= ~_BV(PD5);//output low
}

void n_off(){
    DDRD |=  _BV(PD7); PORTD |=  _BV(PD7);//output high
    DDRD |=  _BV(PD5); PORTD |=  _BV(PD5);//output high
}

float dot(float beats, int dots){
    return beats * (2.0 - powf(2.0,-dots));
}