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Software/NodeJS/libs/sensors/rotaryAngleAnalogSensor.js

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+var AnalogSensor = require('./base/analogSensor')
+var helpers = require('./helpers')
+const FULL_ANGLE = 300
+
+//RotaryAngleSensor
+//returns a value from 0 to 100
+//implemented a basic noise filtering algorithm, as in our experiments
+//the rotary sensor was throwing random values at random times
+function RotaryAngleAnalogSensor(pin, watchDelay, samplesize) {
+    AnalogSensor.apply(this, Array.prototype.slice.call(arguments))
+    this.watchDelay = watchDelay || 10
+    this.samplesize = samplesize || 40
+    //watchDelay * samplesize equals the miliseconds interval that the sensor will report data
+}
+RotaryAngleAnalogSensor.prototype = new AnalogSensor()
+
+RotaryAngleAnalogSensor.prototype.read = function () {
+    let value = AnalogSensor.prototype.read.call(this)
+    
+    let degrees = convertDHTToDegrees(value)
+
+    //Calculate result (0 to 100) from degrees(0 to 300)
+    let result = Math.floor(degrees / FULL_ANGLE * 100)
+
+    return result
+}
+
+const convertDHTToDegrees = function (value) {
+    //http://wiki.seeed.cc/Grove-Rotary_Angle_Sensor/
+    let adc_ref = 5
+    let grove_vcc = 5
+  
+    let voltage = helpers.round((value) * adc_ref / 1023, 2)
+
+    //Calculate rotation in degrees(0 to 300)
+    return helpers.round((voltage * FULL_ANGLE) / grove_vcc, 2)
+}
+
+RotaryAngleAnalogSensor.prototype.start = function () {
+    setInterval(loop.bind(this), this.watchDelay)
+}
+
+RotaryAngleAnalogSensor.prototype.stop = function () {
+    clearInterval(loop)
+}
+
+//new array initialized to zero
+let temp = Array.apply(null, Array(101)).map(Number.prototype.valueOf, 0) //0..100
+let timesRun = 0
+
+let previousData = null
+
+function loop() {
+    const reading = this.read()
+    if (reading < 0 || reading > 100) throw new Error('improper reading')
+
+    temp[reading]++
+    if (++timesRun === this.samplesize) {
+        //find the index of the biggest integer
+        const result = temp.indexOf(Math.max(...temp))
+        timesRun = 0
+        //reset the array
+        temp = Array.apply(null, Array(101)).map(Number.prototype.valueOf, 0)
+        
+        //compare current data to previous data
+        if (previousData === null || Math.abs(result - previousData) != 0) {
+            //there is a new value
+            this.emit('data', result)
+            previousData = result
+        }
+    }
+}
+
+module.exports = RotaryAngleAnalogSensor