File content as of revision 0:2309ea52d6c9:

#define mC 261.626
#define mD 293.665
#define mE 329.628
#define mF 349.228
#define mG 391.995
#define mA 440.000
#define mB 493.883

#include "mbed.h"

Ticker timer;
AnalogOut sp1(p18);
float ms[180];
float m1,m2,m3;

void sound_out(void) {
    static float j1=0;
    static float j2=0;
    static float j3=0;
    j1=j1+m1;
    j2=j2+m2;
    j3=j3+m3;
    if (j1>180)j1=j1-180;
    if (j2>180)j2=j2-180;
    if (j3>180)j3=j3-180;
    sp1.write((ms[(int)j1]+ms[(int)j2]+ms[(int)j3])/3.0);
}

int main() {
    int i;
    //setting sincurv
    for (i=0;i<180;i++) {
        ms[i]=sin(2*3.1415*(float)i/180.0)/2.0+0.5;
    }
    timer.attach_us(&sound_out,10); //10kHz
    //ceg
    m1=mC*2*180/100000;
    m2=mE*2*180/100000;
    m3=mG*2*180/100000;
    wait(1.0f);
    //cfa
    m1=mC*2*180/100000;
    m2=mF*2*180/100000;
    m3=mA*2*180/100000;
    wait(1.0f);
    //ceg
    m1=mC*2*180/100000;
    m2=mE*2*180/100000;
    m3=mG*2*180/100000;
    wait(1.0f);
    //bdg
    m1=mB*180/100000;
    m2=mD*2*180/100000;
    m3=mG*2*180/100000;
    wait(1.0f);
    //ceg
    m1=mC*2*180/100000;
    m2=mE*2*180/100000;
    m3=mG*2*180/100000;
    wait(1.0f);
    timer.detach();
    sp1.write(0.0f);
    while (1);
}