LED Control APK (ESP32. MQTT. Broker. Publish. Subscribe .MIT APP Inventor)

 LED Control APK

(ESP32. MQTT. Broker. Publish. Subscribe .MIT APP Inventor)

https://drive.google.com/file/d/1E9hAdQNrI3N77pO3_a8c07HA9hRLNdUo/view?usp=sharing

WOKWI程式

#include <WiFi.h>

#include <PubSubClient.h>

#include "DHTesp.h"

#include <ArduinoJson.h>

const int DHT_PIN = 15;

const int LED_PIN = 2;

DHTesp dhtSensor;

const char* ssid = "Wokwi-GUEST";

const char* password = "";

const char* mqtt_server = "broker.hivemq.com";

WiFiClient espClient;

PubSubClient client(espClient);

unsigned long lastMsg = 0;

#define MSG_BUFFER_SIZE  (50)

float temp = 0;

float hum = 0;

int value = 0;

//======================================================================================

void setup_wifi() {

  delay(10);

  // We start by connecting to a WiFi network

  Serial.println();

  Serial.print("Connecting to ");

  Serial.println(ssid);

  WiFi.mode(WIFI_STA);

  WiFi.begin(ssid, password);

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

    delay(500);

    Serial.print(".");

  }

  randomSeed(micros());

  Serial.println("");

  Serial.println("WiFi connected");

  Serial.println("IP address: ");

  Serial.println(WiFi.localIP());

}

//======================================================================================

void callback(char* topic, byte* payload, unsigned int length) {

  Serial.print("Message arrived [");

  Serial.print(topic);

  Serial.print("] ");

  String message="";

  for (int i = 0; i < length; i++) {

    Serial.print((char)payload[i]);

    message += ((char)payload[i]);

  }

  Serial.println();

  message.trim();

  // Switch on the LED if an 1 was received as first character

  if (String(topic) == "alex9ufo/esp32/LED") {

    Serial.print("Changing output to ");

    if(message == "on"){

      digitalWrite(LED_PIN, LOW);

    }

    else if(message == "off"){

      digitalWrite(LED_PIN, HIGH);

    }

  }

}

//======================================================================================

void reconnect() {

  // Loop until we're reconnected

  while (!client.connected()) {

    Serial.print("Attempting MQTT connection...");

    // Create a random client ID

    String clientId = "ESP32Client-";

    clientId += String(random(0xffff), HEX);

    // Attempt to connect

    if (client.connect(clientId.c_str())) {

      Serial.println("Connected");

      // Once connected, publish an announcement...

      //client.publish("alex9ufo/esp32", "iotfrontier");

      // ... and resubscribe

      client.subscribe("alex9ufo/esp32/LED");

    } else {

      Serial.print("failed, rc=");

      Serial.print(client.state());

      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying

      delay(5000);

    }

  }

}

//======================================================================================

void setup() {

  pinMode(LED_PIN, OUTPUT);     // Initialize the BUILTIN_LED pin as an output

  digitalWrite(LED_PIN, HIGH);

  Serial.begin(115200);

  setup_wifi();

  client.setServer(mqtt_server, 1883);

  client.setCallback(callback);

  dhtSensor.setup(DHT_PIN, DHTesp::DHT22);

}

//======================================================================================

void loop() {

  if (!client.connected()) {

    reconnect();

  }

  client.loop();

  unsigned long now = millis();

  if (now - lastMsg > 2000) {

    lastMsg = now;

    TempAndHumidity  data = dhtSensor.getTempAndHumidity();

    String temp = String(data.temperature, 2);

    Serial.print("Temperature: ");

    Serial.println(temp);

    client.publish("alex9ufo/esp32/temperature", temp.c_str());

   

    String hum = String(data.humidity, 1);

    Serial.print("Humidity: ");

    Serial.println(hum);

    client.publish("alex9ufo/esp32/humidity", hum.c_str());

  }

}

//======================================================================================