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pwm_song/main.cpp

Committer:
ShawnHymel
Date:
2014-07-28
Revision:
0:6a73d3dc037e

File content as of revision 0:6a73d3dc037e:

// Plays a familiar melody using PWM to the headphones. To find the frequencies
// of notes, see http://en.wikipedia.org/wiki/Piano_key_frequencies
// Based on the "speaker_demo_PWM" program by Jim Hamblen

#include "mbed.h"

#define VOLUME 0.01
#define BPM 100.0

PwmOut pwm_pin(p21);

// Plays a sound with the defined frequency, duration, and volume
void playNote(float frequency, float duration, float volume) {
    pwm_pin.period(1.0/frequency);
    pwm_pin = volume/2.0;
    wait(duration);
    pwm_pin = 0.0;
}

int main()
{
    float beat_duration;

    // Calculate duration of a quarter note from bpm
    beat_duration = 60.0 / BPM;
    
    // Loop forever
    while(1) {
        
        // First measure
        playNote(391.995, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(391.995, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(391.995, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(311.127, (0.75 * beat_duration), VOLUME);
        playNote(466.164, (0.25 * beat_duration), VOLUME);
        
        // Second measure
        playNote(391.995, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(311.127, (0.75 * beat_duration), VOLUME);
        playNote(466.164, (0.25 * beat_duration), VOLUME);
        playNote(391.995, ((2 * beat_duration) - 0.1), VOLUME);
        wait(0.1);
        
        // Third measure
        playNote(587.330, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(587.330, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(587.330, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(622.254, (0.75 * beat_duration), VOLUME);
        playNote(466.164, (0.25 * beat_duration), VOLUME);
        
        // Fourth measure
        playNote(369.994, (beat_duration - 0.1), VOLUME);
        wait(0.1);
        playNote(311.127, (0.75 * beat_duration), VOLUME);
        playNote(466.164, (0.25 * beat_duration), VOLUME);
        playNote(391.995, ((2 * beat_duration) - 0.1), VOLUME);
        wait(0.1);
    }
}