am2320b/lib/am2320.js

Module for reading the raw data from AM2320

var i2c = require('i2c');

function setTimeoutAsync(delay) {
  return new Promise(function(resolve, reject) {
    setTimeout(resolve, delay);
  });
}

function AM2320(address, device) {
  this.device = device || AM2320.DEFAULT_DEVICE_PATH;
  this.address = address || AM2320.DEFAULT_ADDRESS;
  this.initialize();
}

AM2320.DEFAULT_ADDRESS = 0x5c;
AM2320.DEFAULT_DEVICE_PATH = '/dev/i2c-1';
AM2320.READ_INTERVAL_SECONDS = 2;

AM2320.prototype.initialize = function() {
  this.wire = new i2c(this.address, {device : this.device});
}

AM2320.prototype.wakeUpDevice = function() {
  this.wire.writeBytes(0x00, [], function(err) {});
}

AM2320.prototype.setResolution = function() {
  this.wire.writeBytes(0x03, [0x00, 0x04], function(err) {
    if (err) {
      console.error(err);
    }
  });
}

AM2320.prototype._readRawResolution = function() {
  var self = this;
  return new Promise(function(resolve, reject) {
    var diff = process.hrtime(self.lastUpdate);
    if (diff[0] >= AM2320.READ_INTERVAL_SECONDS) {
      self.wakeUpDevice();
      setTimeoutAsync(3)
        .then(function() {
          self.setResolution();
          return setTimeoutAsync(3);
        })
        .then(function() {
          self.wire.readBytes(0x00, 0x06, function(err, res) {
            if (err) {
              reject(err);
              return;
            } else {
              self.lastUpdate = process.hrtime();
              self.lastValue = res;
              resolve(res);
            }
          });
        });
    } else {
      resolve(self.lastValue);
    }
  });
}

AM2320.prototype.readTemperature = function() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self._readRawResolution()
      .then(function(value) {
        resolve((value[4] << 8 | value[5])/10.0);
      })
      .catch(function(value) {
        reject(value);
      });
  });
}

AM2320.prototype.readHumidity = function() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self._readRawResolution()
      .then(function(value) {
        resolve((value[2] << 8 | value[3])/10.0);
      })
      .catch(function(value) {
        reject(value);
      });
  });
}

AM2320.prototype.readBulk = function() {
  var self = this;
  return new Promise(function(resolve, reject) {
    self._readRawResolution()
      .then(function(value) {
        resolve({hum:(value[2] << 8 | value[3])/10.0, temp: ((value[4] << 8 | value[5])/10.0)});
      })
      .catch(function(value) {
        reject(value);
      });
  });
}

module.exports = AM2320;