fpdevice.js

/*******************************************************************************
 *
 * flower-power device abstraction
 *
 * deps:
 * npm install flower-power
 *
 * author: cyrillvw
 *
 * usage example:
 *
 * var fp = new fpdevice(device);
 * fp.set_num_measurements(4);
 * fp.read(function(average, median, data){
 *  console.log(average, median, data);
 * });
 *
 *******************************************************************************/

var fpdevice = function(device) {

  var num_measurements = 3;
  var measurement_ready = [];
  var live_read_count = live_read_data = {};
  var disable_lock = false;
  var ready_callback = function(){};

  // PUBLIC read all aviable data on device. takes about 1 sec * num_measurements
  this.read = function(callback){
    live_read_count = []
    measurement_ready = [];
    live_read_count = [];
    live_read_data = {};
    disable_lock = false;
    device.connectAndSetUp(function(){
      device.enableLiveMode();
      device.enableCalibratedLiveMode();
      device.readBatteryLevel(function(error, data) {
        live_read_data.battery = [data];
      });
      if (callback){
        ready_callback = callback;
      }
    });
  }

  // PUBLIC set number of single measurements per read
  this.set_num_measurements = function(num){
    num_measurements = num;
  }

  // init devices and bind events
  function init(){
    device.on('soilTemperatureChange',            event_data.bind('temp_soil')          );
    device.on('calibratedAirTemperatureChange',   event_data.bind('temp_air')           );
    device.on('calibratedSunlightChange',         event_data.bind('sunlight')           );
    device.on('calibratedSoilMoistureChange',     event_data.bind('soil_moisture')      );
    device.on('calibratedEaChange',               event_data.bind('soil_ea')            );
    device.on('calibratedEcbChange',              event_data.bind('soil_ecb')           );
    device.on('calibratedEcPorousChange',         event_data.bind('soil_ec_porous')     );
    device.on('soilElectricalConductivityChange', event_data.bind('soil_conductivity')  );
  }

  // gets triggered when an event occured aka measurement data
  function event_data(data) {
    if (!live_read_data[this]){
      live_read_data[this] = [];
      live_read_count[this] = [0];
      measurement_ready[this] = false;
    }
    if (!measurement_ready[this]){
      live_read_count[this]++;
      live_read_data[this].push(data);
      if (live_read_count[this] > (num_measurements-1) ) {
        measurement_ready[this] = true;
        check_ready(this);
      }
    }
    else {
      check_ready(this);
    }
  }

  // checks if all measurements are ready
  function check_ready(){
    var arr_ready = true;
    for (item of measurement_ready){
      var chk = measurement_ready[item];
      if (!measurement_ready[item]){
        arr_ready = false;
      }
    }
    if (arr_ready == true && disable_lock == false){
      disable_lock = true;
      device.disableLiveMode(function(){
        device.disableCalibratedLiveMode(function(){
          device.disconnect(function(){
            disable_lock = false;
            calculate_result();
          });
        });
      });
    }
  }

  // calculate average
  function arr_average(values){
    var num  = values.reduce(function(a, b) {
      return parseFloat(a) + parseFloat(b);
    });
    return (num / values.length);
  }

  // calculate median
  function arr_median(values) {
    values.sort( function(a,b) {return a - b;} );
    var half = Math.floor(values.length/2);
    if(values.length % 2){
        return values[half];
    }
    else {
      return (values[half-1] + values[half]) / 2.0;
    }
  }

  // calculate result and trigger callback
  function calculate_result(){
    var average = {};
    var median = {};
    for (item in live_read_data){
      average[item] = arr_average(live_read_data[item]);
      median[item] = arr_median(live_read_data[item]);
    }
    ready_callback(average, median, live_read_data);
  }

  init();
  return this;
}



module.exports = fpdevice;