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Rui Santos
Complete project details at
The above copyright notice and this permission notice shall be included in all
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// Import required libraries
#include "ESP8266WiFi.h"
#include "ESPAsyncWebServer.h"
// Set to true to define Relay as Normally Open (NO)
#define RELAY_NO true
// Set number of relays
#define NUM_RELAYS 5
// Assign each GPIO to a relay
int relayGPIOs[NUM_RELAYS] = {2, 4, 14, 12, 13};
// Replace with your network credentials
const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";
const char* PARAM_INPUT_1 = "relay";
const char* PARAM_INPUT_2 = "state";
// Create AsyncWebServer object on port 80
AsyncWebServer server(80);
const char index_html[] PROGMEM = R"rawliteral(
<meta name="viewport" content="width=device-width, initial-scale=1">
html {font-family: Arial; display: inline-block; text-align: center;}
h2 {font-size: 3.0rem;}
p {font-size: 3.0rem;}
body {max-width: 600px; margin:0px auto; padding-bottom: 25px;}
.switch {position: relative; display: inline-block; width: 120px; height: 68px}
.switch input {display: none}
.slider {position: absolute; top: 0; left: 0; right: 0; bottom: 0; background-color: #ccc; border-radius: 34px}
.slider:before {position: absolute; content: ""; height: 52px; width: 52px; left: 8px; bottom: 8px; background-color: #fff; -webkit-transition: .4s; transition: .4s; border-radius: 68px}
input:checked+.slider {background-color: #2196F3}
input:checked+.slider:before {-webkit-transform: translateX(52px); -ms-transform: translateX(52px); transform: translateX(52px)}
<h2>ESP Web Server</h2>
<script>function toggleCheckbox(element) {
var xhr = new XMLHttpRequest();
if(element.checked){"GET", "/update?relay=""&state=1", true); xhr.send();
setTimeout(function(){"GET", "/update?relay=""&state=0", true); document.getElementById( = false; xhr.send(); }, 1000);}
// Replaces placeholder with button section in your web page
String processor(const String& var){
String buttons ="";
for(int i=1; i<=NUM_RELAYS; i++){
String relayStateValue = relayState(i);
buttons+= "<h4>Relay #" + String(i) + " - GPIO " + relayGPIOs[i-1] + "</h4><label class=\"switch\"><input type=\"checkbox\" onchange=\"toggleCheckbox(this)\" id=\"" + String(i) + "\" "+ relayStateValue +"><span class=\"slider\"></span></label>";
return buttons;
return String();
String relayState(int numRelay){
return "";
else {
return "checked";
else {
return "checked";
else {
return "";
return "";
void setup(){
// Serial port for debugging purposes
// Set all relays to off when the program starts - if set to Normally Open (NO), the relay is off when you set the relay to HIGH
for(int i=1; i<=NUM_RELAYS; i++){
pinMode(relayGPIOs[i-1], OUTPUT);
digitalWrite(relayGPIOs[i-1], HIGH);
digitalWrite(relayGPIOs[i-1], LOW);
// Connect to Wi-Fi
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
Serial.println("Connecting to WiFi..");
// Print ESP8266 Local IP Address
// Route for root / web page
server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
request->send_P(200, "text/html", index_html, processor);
// Send a GET request to <ESP_IP>/update?relay=<inputMessage>&state=<inputMessage2>
server.on("/update", HTTP_GET, [] (AsyncWebServerRequest *request) {
String inputMessage;
String inputParam;
String inputMessage2;
String inputParam2;
// GET input1 value on <ESP_IP>/update?relay=<inputMessage>
if (request->hasParam(PARAM_INPUT_1) & request->hasParam(PARAM_INPUT_2)) {
inputMessage = request->getParam(PARAM_INPUT_1)->value();
inputParam = PARAM_INPUT_1;
inputMessage2 = request->getParam(PARAM_INPUT_2)->value();
inputParam2 = PARAM_INPUT_2;
Serial.print("NO ");
digitalWrite(relayGPIOs[inputMessage.toInt()-1], !inputMessage2.toInt());
Serial.print("NC ");
digitalWrite(relayGPIOs[inputMessage.toInt()-1], inputMessage2.toInt());
else {
inputMessage = "No message sent";
inputParam = "none";
Serial.println(inputMessage + inputMessage2);
request->send(200, "text/plain", "OK");
// Start server
void loop() {
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