Recording and analyzing sound

Ok, FFT is now fixed, and will be in the 1v92 release.

When 1v92 is released you'll be able to use this (slightly cleaner & faster) code:

var w = new Waveform(512,{doubleBuffer:true,bits:16});
var a = new Uint16Array(512);
w.on("buffer", function(buf) {
  a.set(buf);
  E.FFT(a);
  var m=0,n=-1;
  for (var i=150;i<250;i++)if(a[i]>n)n=a[m=i];
  console.log(m.toFixed(0)+"Hz @ "+n);
});
w.startInput(D2,512,{repeat:true});

The 'for' loop is intentionally quite tight - Espruino's execution speed isn't that fast so I'm trying to make it as quick as possible.

The @ xxx part that's printed is the volume of the most prominent frequency. If no frequency is playing then you'll get a random frequency shown, but with a lower volume.

Also, just a note: don't expect great battery life when using this. Realistically you'll need to use a bigger power source if you want to get more than a day's life out of it.