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Exercise 2.2 - Sensors

e) Human interaction

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

Enter a threshold for the temperature and press "Set threshold". When the threshold is exceeded, the LED will turn red and the hardware button starts blinking.

script.js

This is the JavaScript code behind the above application.

/* global writeLog, getInput, tf */
writeLog("Solution for exercise 2.2 e) Human interaction");
// Create a global variable to store the found devices
var devices;
var temperatureSensor;
var led;
var btn;
// Global variable to remember whether action was taken
var temperatureExceeded = false;
// Create a global variable for the temperatur threshold
// Set initial threshold to 25° C
var temperatureThreshold = 25;
// 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);
// Get notified about temperatures changes
 temperatureSensor.registerListener(temperatureOrHumidityChanged);
// Get the RGB LED
 led = devices.getDeviceByIdentifier(271);
// Set the LED off on startup
 led.off();
// Get the RGB LED button and turn it off
 btn = devices.getDeviceByIdentifier(282);
 btn.off();
// Get notified when button is pressed
 btn.registerListener(buttonChanged);
}
function setThreshold() {
 temperatureThreshold = getInput("temperatureThreshold");
 writeLog("New threshold: " + temperatureThreshold);
}
// This function is the callback for when the button is PRESSED or RELEASED
function buttonChanged(event) {
 var btnState = event.getValue();
 writeLog(btnState);
if (btnState === "RELEASED") {
 writeLog("Turning it off")
 led.off();
 btn.off();
 }
}
function temperatureOrHumidityChanged(event) {
var temperature = event.getValue("temperature");
// Do nothing if this is not a temperature update (but rather humidity)
 if (temperature == null) {
 return;
 }
// Format the temperature and add unit
 let temperatureFormatted = (temperature / 100).toFixed(2) + "° C";
// Get the display element from the HTML via its ID
 var displayElement = document.getElementById("temperatureDisplay");
// Update the temperature display
 displayElement.textContent = temperatureFormatted;
// Check if the threshold is exceeded
 if (temperature >= temperatureThreshold * 100) {
if (!temperatureExceeded) {
 writeLog("Warning: Temperature threshold exceeded: " + temperatureFormatted);
// Set LED to red
 led.setColor(255, 0, 0);
// Make the hardware button start blinking white
 btn.blink(255, 255, 255, 500);
// Make the display's background red
 displayElement.parentElement.classList.remove("alert-success");
 displayElement.parentElement.classList.add("alert-danger");
 }
// Remember that the temperature is exceeded
 temperatureExceeded = true;
 }
 else {
 led.off();
// Make the display's background green again
 displayElement.parentElement.classList.remove("alert-danger");
 displayElement.parentElement.classList.add("alert-success");
// Remember that the temperature is OK again
 temperatureExceeded = false;
 }
}