File content as of revision 1:1eefeb256849:

#include "mbed.h"       // this tells us to load mbed related functions
#include "tones.h"                   // list of all the tones and their frequencies

InterruptIn btn2(SW2);               // we create a variable 'btn2', use it as an in port
InterruptIn btn3(SW3);               // we create a variable 'btn3', use it as an in port

PwmOut buzzer(D3);                   // our buzzer is a PWM output (pulse-width modulation)

Timeout tone_timeout;  //TimeOut = a interrupt to call a function after a specified delay

static void silence() {
    buzzer.write(0.0f); // silence!
}

// this is our function that plays a tone. 
// Takes in a tone frequency, and after duration (in ms.) we stop playing again
static void play_tone(int tone, int duration) {
    buzzer.period_us(1000000/(tone));
    buzzer.write(0.10f); // 10% duty cycle, otherwise it's too loud
    
    // we wait for duration ms. and then call the silence function
    tone_timeout.attach_us(&silence, duration*1000); // setup tone_timeout to call silence after duration ms
}

// YOUR CODE HERE

// this code runs when the microcontroller starts up
int main() {
    btn2.fall(play_note1);
    btn3.fall(play_note2);
}