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Exercise 2.3 - Display

b) Display and update sensor values

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

The display should now show the current sensor values and update them frequently.

script.js

This is the JavaScript code behind the above application.

/* global writeLog, getInput, tf */
writeLog("Solution for exercise 2.3 b) Display and update sensor values");
// Create a global variable to store the found devices
var devices;
var oled;
var sensor;
var currentTemperature = 20;
var currentHumidity = 50;
// 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 OLED display
 oled = devices.getDeviceByIdentifier(263);
// Get the temperature/humidity sensor
 sensor = devices.getDeviceByIdentifier(283);
// Print the welcome message
 printWelcome();
// Wait 5 seconds before registering the listener
 // More info here: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Asynchronous/Timeouts_and_intervals
 setTimeout(() => {
 oled.clearDisplay();
 sensor.registerListener(sensorChanged);
 }, 5000);
}
function sensorChanged(event) {
 var newTemperature = event.getValue("temperature");
 var newHumidity = event.getValue("humidity");
// This is a shortcut for an if..else statement
 currentTemperature = newTemperature === null ? currentTemperature : newTemperature;
 currentHumidity = newHumidity === null ? currentHumidity : newHumidity;
// Update the display
oled.write(0, 0, "Temperature: " + (currentTemperature / 100).toFixed(2) + " C");
 oled.write(1, 0, "Humidity : " + (currentHumidity / 100).toFixed(2) + " %");
}
// The welcome message is in it own function now
function printWelcome() {
 var welcomeMessage = "Welcome to my application!"
 oled.clearDisplay();
 oled.write(0, 0, welcomeMessage);
 writeLog(welcomeMessage);
}