In this example we will use the Espressif ESP32 working as Web server with WiFi connection, that host a web page witch allows to control on-off state of two relays. This can be util for to drive high voltage loads connected to 110VAC or 220VAC, such as motors, electrovalves, contactors, etc.
For the compete code, follow the link to GitHub
/*********
ESP32 Web server
Includes an lcd H44780 conected via I2C bus. The IP addres obtained via
DHCP protocol is printed in the display.
The dispay even shows the status of each of two relays conected
and handled by the HTML code.
This sketch it is based on the Rui Santos original Web server example
and was modified by me in Ramos Mejía, ARGENTINA, August 2020.
- Osvaldo Cantone correo@cantone.com.ar
reles:
Relé1 GPIO.15
Relé2 GPIO.2
display:
SDA GPIO.21
SCL GPIO.22
*********/
#include <Arduino.h>
#include <WiFi.h>
#include <LiquidCrystal_PCF8574.h>
#include <Wire.h>
LiquidCrystal_PCF8574 lcd(0x27); // set the LCD address to 0x27 for a 16 chars and 2 line display
// Replace the X's with your network credentials
const char* ssid = "XXXXXXXXXXXXX";
const char* password = "XXXXXXXXXXXXX";
// 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 relay1State = "off";
String relay2State = "off";
// Assign output variables to GPIO pins
//const int output26 = 26;
//const int output27 = 27;
const int Relay1 = 15;
const int Relay2 = 2;
// Current time
unsigned long currentTime = millis();
// Previous time
unsigned long previousTime = 0;
// Define timeout time in milliseconds (example: 2000ms = 2s)
const long timeoutTime = 2000;
int show = -1;
void setup() {
int error;
Serial.begin(9600);
// Initialize the output variables as outputs
pinMode(Relay1, OUTPUT);
pinMode(Relay2, OUTPUT);
// Set outputs to LOW
digitalWrite(Relay1, LOW);
digitalWrite(Relay2, LOW);
//Initializing the display
Wire.begin();
Wire.beginTransmission(0x27);
error = Wire.endTransmission();
Serial.print("Error: ");
Serial.print(error);
if (error == 0) {
Serial.println(": LCD found.");
show = 0;
lcd.begin(16, 2); // initialize the lcd
} else {
Serial.println(": LCD not found.");
} // if
lcd.setBacklight(255);
lcd.home();
lcd.clear();
lcd.setCursor(0, 0);
// lcd.print("0123456789ABCDEF");
lcd.print(" ESP32 WebSerer ");
// 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());
lcd.setCursor(0, 1);
lcd.print(WiFi.localIP());
delay(2000);
lcd.setCursor(0, 0);
lcd.print("ESP32 ");
lcd.print(WiFi.localIP());
lcd.setCursor(0, 1);
lcd.print("R1: ON R2: ON ");
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");
relay1State = "on";
digitalWrite(Relay1, HIGH);
lcd.setCursor(4, 1);
lcd.print("OFF");
} else if (header.indexOf("GET /26/off") >= 0) {
Serial.println("GPIO 26 off");
relay1State = "off";
digitalWrite(Relay1, LOW);
lcd.setCursor(4, 1);
lcd.print("ON ");
} else if (header.indexOf("GET /27/on") >= 0) {
Serial.println("GPIO 27 on");
relay2State = "on";
digitalWrite(Relay2, HIGH);
lcd.setCursor(13, 1);
lcd.print("OFF");
} else if (header.indexOf("GET /27/off") >= 0) {
Serial.println("GPIO 27 off");
relay2State = "off";
digitalWrite(Relay2, LOW);
lcd.setCursor(13, 1);
lcd.print("ON ");
}
// 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>");
client.println("<p>Adapted by Osvaldo Cantone <a href=http://www.cantone.com.ar/wordpress/esp32-web-server-relay-control-lcd-i2c-display/>tecteach.net</a> </p>");
// Display current state, and ON/OFF buttons for GPIO 26
client.println("<p>Relay 1 (GPIO 15) - State: " + relay1State + "</p>");
// If the output26State is off, it displays the ON button
if (relay1State=="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>Relay 2 (GPIO 2) - State: " + relay2State + "</p>");
// If the output27State is off, it displays the ON button
if (relay2State=="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("");
}
}