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Exercise 2.2 - Sensors

b) Read the temperature and humidity

This is the console. All output created with writeLog() is shown here.

Press the button to start reading the temperature and humidity information.

script.js

This is the JavaScript code behind the above application.

/* global writeLog, getInput, tf */
writeLog("Solution for exercise 2.2 b) Read the temperature and humidity");
// Create a global variable to store the found devices
var devices;
var temperatureSensor;
// Initialite connected devices
tf.initDevices(initDone);
// Call this when all connections are established
function initDone(connectedDevices) {
if (connectedDevices.length === 0) {
 writeLog("Oops, didn't find any devices! Make sure they are connected and refresh this page!");
 }
// Store the devices on the global variable
 devices = connectedDevices;
// Get the humidty sensor (includes temperature)
 temperatureSensor = devices.getDeviceByIdentifier(283);
}
function startReadingTemperatureAndHumidity() {
 writeLog("Start to read the temperature and humidity.")
 temperatureSensor.listen(temperatureOrHumidityChanged);
 temperatureSensor.setCallbackInterval(5000);
}
function temperatureOrHumidityChanged(event) {
// We know there is only one value per call
 var valueObject = event.values[0];
// Convert the value into the right scale
 var value = valueObject.value / 100;
if (valueObject.type === "temperature") {
 writeLog("Temperature: " + value.toFixed(2) + " °C");
 }
 else if (valueObject.type === "humidity") {
 writeLog("Humidity: " + value.toFixed(2) + " %");
 }
}