INTERNET OF THINGS (IOT) : CHO NGƯỜI MỚI BẮT ĐẦU

ESP32 Arduino:

#include <WiFi.h>
#include <PubSubClient.th>
#include <string.h>
#include <DHT.h>

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

// Add your MQTT Broker IP address, example:
//const char* mqtt_server = “192.168.1.144”;
const char* mqtt_server = “YOUR_MQTT_BROKER_IP_ADDRESS”;

// Digital pin connected to the DHT sensor
#define DHTPIN 4

// Uncomment whatever DHT sensor type you’re using
//#define DHTTYPE DHT11 // DHT 11
#define DHTTYPE DHT22 // DHT 22 (AM2302), AM2321
//#define DHTTYPE DHT21 // DHT 21 (AM2301)

// Initialize DHT sensor
DHT dht(DHTPIN, DHTTYPE);

void setup(){
Serial.begin(115200);
dht.begin();
setup_wifi();
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
pinMode(ledPin, OUTPUT);
}

void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
Serial.println();
Serial.print(“Connecting to “);
Serial.println(ssid);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(“.”);
}

Serial.println(“”);
Serial.println(“WiFi connected”);
Serial.println(“IP address: “);
Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* message, unsigned int length) {
Serial.print(“Message arrived on topic: “);
Serial.print(topic);
Serial.print(“. Message: “);
String messageTemp;

for (int i = 0; i < length; i++) {
Serial.print((char)message[i]);
messageTemp += (char)message[i];
}
Serial.println();

// Feel free to add more if statements to control more GPIOs with MQTT

// If a message is received on the topic esp32/output, you check if the message is either “on” or “off”.
// Changes the output state according to the message
if (String(topic) == “esp32/output”) {
Serial.print(“Changing output to “);
if(messageTemp == “on”){
Serial.println(“on”);
digitalWrite(ledPin, HIGH);
}
else if(messageTemp == “off”){
Serial.println(“off”);
digitalWrite(ledPin, LOW);
}
}
}

void reconnect() {
// Loop until we’re reconnected
while (!client.connected()) {
Serial.print(“Attempting MQTT connection…”);
// Attempt to connect
if (client.connect(“ESP32Client”)) {
Serial.println(“connected”);
// Subscribe
client.subscribe(“esp32/output”);
} else {
Serial.print(“failed, rc=”);
Serial.print(client.state());
Serial.println(” try again in 5 seconds”);
// Wait 5 seconds before retrying
delay(5000);
}
}
}

void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();

long now = millis();
if (now – lastMsg > 5000) {
lastMsg = now;

//Get tempatature and humidity
// New DHT sensor readings
humidity = dht.readHumidity();
// Read temperature as Celsius (the default)
temperature = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
//temp = dht.readTemperature(true);

// Check if any reads failed and exit early (to try again).
if (isnan(temp) || isnan(hum)) {
Serial.println(F(“Failed to read from DHT sensor!”));
return;
}

// Convert the value to a char array
char tempString[8];
dtostrf(temperature, 1, 2, tempString);
Serial.print(“Temperature: “);
Serial.println(tempString);
client.publish(“esp32/temperature”, tempString);

// Convert the value to a char array
char humString[8];
dtostrf(humidity, 1, 2, humString);
Serial.print(“Humidity: “);
Serial.println(humString);
client.publish(“esp32/humidity”, humString);
}
}
// converts character array
// to string and returns it
String convertToString(char* a, int size)
{
int i;
String s = “”;
for (i = 0; i < size; i++) {
s = s + a[i];
}
return s;
}