Come creare web app per gestire LED su ESP32 #13

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Nell’articolo di oggi vedremo come utilizzare realizzare una web app (o server web totalmente autonomo) con ESP32. Il progetto in questione controllerà due pin GPIO ai quali sono collegati a due LED. Utilizzeremo Arduino IDE. Potremmo accedere con qualsiasi device su rete locale.

Lista componenti

ESP32-WROVER
Breadboard
2x led
3x jumper
GPIO extension board (falcolatitivo)

Fasi salienti del progetto

Il server gestirà due pin GPIO.

Sarà possibile accedere al server WEB digitando l’indirizzo IP dell’ESP32 su broswer (rete locale).

Cliccando i bottoni che compariranno sul web server si può cambiare lo stato del LED da accesso a spento e viceversa.

Collegamenti

In seguito schema e diagramma di collegamento. Per costruire un circuito ricordati di tenere la scheda spenta.

Codice

Se questo è il tuo primo articolo ti invito di leggere prima questo per l’installazione dei driver della scheda. Ecco qui un piccolo riepilogo prima di compilare e caricare il codice.

Ecco qui lo sketch:

// Load Wi-Fi library
#include &lt;WiFi.h&gt;

// Replace with your network credentials
const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";

// Set web server port number to 80
WiFiServer server(80);

// Variable to store the HTTP request
String header;

// Auxiliar variables to store the current output state
String output26State = "off";
String output27State = "off";

// Assign output variables to GPIO pins
const int output26 = 26;
const int output27 = 27;

// Current time
unsigned long currentTime = millis();
// Previous time
unsigned long previousTime = 0; 
// Define timeout time in milliseconds (example: 2000ms = 2s)
const long timeoutTime = 2000;

void setup() {
  Serial.begin(115200);
  // Initialize the output variables as outputs
  pinMode(output26, OUTPUT);
  pinMode(output27, OUTPUT);
  // Set outputs to LOW
  digitalWrite(output26, LOW);
  digitalWrite(output27, LOW);

  // Connect to Wi-Fi network with SSID and password
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  // Print local IP address and start web server
  Serial.println("");
  Serial.println("WiFi connected.");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
  server.begin();
}

void loop(){
  WiFiClient client = server.available();   // Listen for incoming clients

  if (client) {                             // If a new client connects,
    currentTime = millis();
    previousTime = currentTime;
    Serial.println("New Client.");          // print a message out in the serial port
    String currentLine = "";                // make a String to hold incoming data from the client
    while (client.connected() &amp;&amp; currentTime - previousTime &lt;= timeoutTime) {  // loop while the client's connected
      currentTime = millis();
      if (client.available()) {             // if there's bytes to read from the client,
        char c = client.read();             // read a byte, then
        Serial.write(c);                    // print it out the serial monitor
        header += c;
        if (c == '\n') {                    // if the byte is a newline character
          // if the current line is blank, you got two newline characters in a row.
          // that's the end of the client HTTP request, so send a response:
          if (currentLine.length() == 0) {
            // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
            // and a content-type so the client knows what's coming, then a blank line:
            client.println("HTTP/1.1 200 OK");
            client.println("Content-type:text/html");
            client.println("Connection: close");
            client.println();
            
            // turns the GPIOs on and off
            if (header.indexOf("GET /26/on") &gt;= 0) {
              Serial.println("GPIO 26 on");
              output26State = "on";
              digitalWrite(output26, HIGH);
            } else if (header.indexOf("GET /26/off") &gt;= 0) {
              Serial.println("GPIO 26 off");
              output26State = "off";
              digitalWrite(output26, LOW);
            } else if (header.indexOf("GET /27/on") &gt;= 0) {
              Serial.println("GPIO 27 on");
              output27State = "on";
              digitalWrite(output27, HIGH);
            } else if (header.indexOf("GET /27/off") &gt;= 0) {
              Serial.println("GPIO 27 off");
              output27State = "off";
              digitalWrite(output27, LOW);
            }
            
            // Display the HTML web page
            client.println("&lt;!DOCTYPE html&gt;&lt;html&gt;");
            client.println("&lt;head&gt;&lt;meta name=\"viewport\" content=\"width=device-width, initial-scale=1\"&gt;");
            client.println("&lt;link rel=\"icon\" href=\"data:,\"&gt;");
            // CSS to style the on/off buttons 
            // Feel free to change the background-color and font-size attributes to fit your preferences
            client.println("&lt;style&gt;html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");
            client.println(".button { background-color: #4CAF50; border: none; color: white; padding: 16px 40px;");
            client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");
            client.println(".button2 {background-color: #555555;}&lt;/style&gt;&lt;/head&gt;");
            
            // Web Page Heading
            client.println("&lt;body&gt;&lt;h1&gt;ESP32 Web Server&lt;/h1&gt;");
            
            // Display current state, and ON/OFF buttons for GPIO 26  
            client.println("&lt;p&gt;GPIO 26 - State " + output26State + "&lt;/p&gt;");
            // If the output26State is off, it displays the ON button       
            if (output26State=="off") {
              client.println("&lt;p&gt;&lt;a href=\"/26/on\"&gt;&lt;button class=\"button\"&gt;ON&lt;/button&gt;&lt;/a&gt;&lt;/p&gt;");
            } else {
              client.println("&lt;p&gt;&lt;a href=\"/26/off\"&gt;&lt;button class=\"button button2\"&gt;OFF&lt;/button&gt;&lt;/a&gt;&lt;/p&gt;");
            } 
               
            // Display current state, and ON/OFF buttons for GPIO 27  
            client.println("&lt;p&gt;GPIO 27 - State " + output27State + "&lt;/p&gt;");
            // If the output27State is off, it displays the ON button       
            if (output27State=="off") {
              client.println("&lt;p&gt;&lt;a href=\"/27/on\"&gt;&lt;button class=\"button\"&gt;ON&lt;/button&gt;&lt;/a&gt;&lt;/p&gt;");
            } else {
              client.println("&lt;p&gt;&lt;a href=\"/27/off\"&gt;&lt;button class=\"button button2\"&gt;OFF&lt;/button&gt;&lt;/a&gt;&lt;/p&gt;");
            }
            client.println("&lt;/body&gt;&lt;/html&gt;");
            
            // The HTTP response ends with another blank line
            client.println();
            // Break out of the while loop
            break;
          } else { // if you got a newline, then clear currentLine
            currentLine = "";
          }
        } else if (c != '\r') {  // if you got anything else but a carriage return character,
          currentLine += c;      // add it to the end of the currentLine
        }
      }
    }
    // Clear the header variable
    header = "";
    // Close the connection
    client.stop();
    Serial.println("Client disconnected.");
    Serial.println("");
  }
}

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// Load Wi-Fi library

#include <WiFi.h>

// Replace with your network credentials

const char* ssid = "REPLACE_WITH_YOUR_SSID";

const char* password = "REPLACE_WITH_YOUR_PASSWORD";

// Set web server port number to 80

WiFiServer server(80);

// Variable to store the HTTP request

String header;

// Auxiliar variables to store the current output state

String output26State = "off";

String output27State = "off";

// Assign output variables to GPIO pins

const int output26 = 26;

const int output27 = 27;

// Current time

unsigned long currentTime = millis();

// Previous time

unsigned long previousTime = 0;

// Define timeout time in milliseconds (example: 2000ms = 2s)

const long timeoutTime = 2000;

void setup() {

Serial.begin(115200);

// Initialize the output variables as outputs

pinMode(output26, OUTPUT);

pinMode(output27, OUTPUT);

// Set outputs to LOW

digitalWrite(output26, LOW);

digitalWrite(output27, LOW);

// Connect to Wi-Fi network with SSID and password

Serial.print("Connecting to ");

Serial.println(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {

delay(500);

Serial.print(".");

}

// Print local IP address and start web server

Serial.println("");

Serial.println("WiFi connected.");

Serial.println("IP address: ");

Serial.println(WiFi.localIP());

server.begin();

}

void loop(){

WiFiClient client = server.available(); // Listen for incoming clients

if (client) { // If a new client connects,

currentTime = millis();

previousTime = currentTime;

Serial.println("New Client."); // print a message out in the serial port

String currentLine = ""; // make a String to hold incoming data from the client

while (client.connected() && currentTime - previousTime <= timeoutTime) { // loop while the client's connected

currentTime = millis();

if (client.available()) { // if there's bytes to read from the client,

char c = client.read(); // read a byte, then

Serial.write(c); // print it out the serial monitor

header += c;

if (c == '\n') { // if the byte is a newline character

// if the current line is blank, you got two newline characters in a row.

// that's the end of the client HTTP request, so send a response:

if (currentLine.length() == 0) {

// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)

// and a content-type so the client knows what's coming, then a blank line:

client.println("HTTP/1.1 200 OK");

client.println("Content-type:text/html");

client.println("Connection: close");

client.println();

// turns the GPIOs on and off

if (header.indexOf("GET /26/on") >= 0) {

Serial.println("GPIO 26 on");

output26State = "on";

digitalWrite(output26, HIGH);

} else if (header.indexOf("GET /26/off") >= 0) {

Serial.println("GPIO 26 off");

output26State = "off";

digitalWrite(output26, LOW);

} else if (header.indexOf("GET /27/on") >= 0) {

Serial.println("GPIO 27 on");

output27State = "on";

digitalWrite(output27, HIGH);

} else if (header.indexOf("GET /27/off") >= 0) {

Serial.println("GPIO 27 off");

output27State = "off";

digitalWrite(output27, LOW);

}

// Display the HTML web page

client.println("<!DOCTYPE html><html>");

client.println("<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");

client.println("<link rel=\"icon\" href=\"data:,\">");

// CSS to style the on/off buttons

// Feel free to change the background-color and font-size attributes to fit your preferences

client.println("<style>html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");

client.println(".button { background-color: #4CAF50; border: none; color: white; padding: 16px 40px;");

client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");

client.println(".button2 {background-color: #555555;}</style></head>");

// Web Page Heading

client.println("<body><h1>ESP32 Web Server</h1>");

// Display current state, and ON/OFF buttons for GPIO 26

client.println("<p>GPIO 26 - State " + output26State + "</p>");

// If the output26State is off, it displays the ON button

if (output26State=="off") {

client.println("<p><a href=\"/26/on\"><button class=\"button\">ON</button></a></p>");

} else {

client.println("<p><a href=\"/26/off\"><button class=\"button button2\">OFF</button></a></p>");

}

// Display current state, and ON/OFF buttons for GPIO 27

client.println("<p>GPIO 27 - State " + output27State + "</p>");

// If the output27State is off, it displays the ON button

if (output27State=="off") {

client.println("<p><a href=\"/27/on\"><button class=\"button\">ON</button></a></p>");

} else {

client.println("<p><a href=\"/27/off\"><button class=\"button button2\">OFF</button></a></p>");

}

client.println("</body></html>");

// The HTTP response ends with another blank line

client.println();

// Break out of the while loop

break;

} else { // if you got a newline, then clear currentLine

currentLine = "";

}

} else if (c != '\r') { // if you got anything else but a carriage return character,

currentLine += c; // add it to the end of the currentLine

}

// Clear the header variable

header = "";

// Close the connection

client.stop();

Serial.println("Client disconnected.");

Serial.println("");

}

Compila e carica il codice sull’ESP32, ed ecco qui che potremo visualizzare l’indirizzo IP che utilizzeremo per accedere via broswer dal monitor seriale.

Accesso server web

Per accedere al server web, apri il browser, incolla l’indirizzo IP di ESP32 e vedrai la pagina seguente.

Ora puoi verificare se il tuo server web funziona correttamente. Fare clic sui pulsanti per controllare l’accensione e spegmineto di LED.

Al prossimo articolo. Grazie per la lettura.

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Simone Candido

Simone Candido è un ragazzo appassionato del mondo tech nella sua totalità. Simone ama immedesimarsi in nuove esperienze, la sua filosofia si basa sulla irrefrenabile voglia di ampliare a 360° le sue conoscenze abbracciando tutti i campi del sapere, in quanto ritiene che il sapere umano sia il connubio perfetto tra cultura umanistica e scientifica.