servo.js

var b = require('bonescript');
var SERVO = 'P9_14';
var duty_min = 0.03;
var position = 0;
var increment = 0.01;
var scale = 0.090;

//b.pinMode(SERVO, b.OUTPUT);
updateDuty();

function updateDuty() {
    var duty_cycle = (position*scale) + duty_min;
    b.analogWrite(SERVO, duty_cycle, 60, scheduleNextUpdate);
}

function scheduleNextUpdate() {
    setTimeout(doRead, 20);
}

function doRead() {
    b.analogRead('P9_36', onRead);
}

function onRead(x) {
    if(!x.err) {
        position = x.value;
    }
    updateDuty();
}