@growbox/sensors/src/sensors/Dht22Sensor.js

An abstraction layer for a selection of raspberry-compatible sensors

/**
 * @author nstCactus
 * @date 06/12/2017 12:45
 */

const dht            = require('node-dht-sensor');
const AbstractSensor = require('./AbstractSensor');
const SensorValue    = require('../SensorValue');

/** {WeakMap<number>} The GPIO pin the sensor is connected to */
let _gpioPin = new WeakMap();

/**
 * A DHT22 temperature and humidity sensor
 */
class Dht22Sensor extends AbstractSensor {
  constructor(name, gpioPin) {
    super(name, `Dht22_gpio${gpioPin}`);

    _gpioPin = gpioPin.set(this, gpioPin);
  }

  /**
   * @returns {number} The GPIO pin the sensor is connected to
   */
  get gpioPin() {
    return _gpioPin.get(this);
  }

  /**
   * Read form the sensor to get the current temperature and relative humidity.
   * @returns {Promise<SensorValue[]>} A promise that, when fulfilled, contains an array of two SensorValues:
   *                                     - the current temperature
   *                                     - the current relative humidity
   */
  read() {
    return new Promise((resolve, reject) => {
      try {
        const reading = dht.read(22, _gpioPin.get(this));

        resolve([
          new SensorValue(SensorValue.TypeEnum.temperature, reading.temperature),
          new SensorValue(SensorValue.TypeEnum.humidity, reading.humidity),
        ]);
      } catch (err) {
        console.error(err);
        // TODO: pass err as well
        reject(new Error(`Skipping dht sensor ${this.name} as an error occurred while reading from it`));
      }
    });
  }
}


module.exports = Dht22Sensor;