Creating a Block in Blockly

Blocking is really bad idea in Espruino, so it's intentionally made really difficult! Espruino isn't pre-emptive so a long loop like that stop all other timers/watches from executing.

Is there any reason you can't do the following:

setTimeout(function() {
  analogWrite(C6, 2.0 / 50.0, {freq:20});
  setTimeout(function() {
    analogWrite(C6, 1.0 / 50.0, {freq:20});
  },4000);
},4000);

That will execute the first timeout, and will then start the second one once the first has completed...