經由MQTT協定的2個WOKWI ESP32 雙向通訊 (ESP32 to ESP32 MQTT Communication )

 經由MQTT協定的2個WOKWI ESP32 雙向通訊 (ESP32  to ESP32 MQTT Communication )

使用兩個 ESP32 建立一個遠端控制系統。

MQTT Broker: mqtt-dashboard.com
Topic (主題): alex9ufo/switchPB

訊息內容: on, off, flash, timer

發送： 按鈕去彈跳並循環發送 on/off/flash/timer 到 alex9ufo/switchPB。

接收： 訂閱 alex9ufo/DHT22，解析 JSON 格式並顯示於 LCD。

執行： 訂閱 alex9ufo/switchPB 控制 LED 動作。
發送： 每 2 秒讀取 DHT22 數據並發行 JSON 到 alex9ufo/DHT22。

引腳連接提醒：

• Button: GPIO 34 (外部下拉電阻)。

• LCD: SDA=21, SCL=22。

• LED: GPIO 2。

• DHT22: GPIO 15。

發送端：按鈕 + LCD (含序列埠監控)

#include <WiFi.h>

#include <PubSubClient.h>

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

#include <ArduinoJson.h>

const int buttonPin = 34;

LiquidCrystal_I2C lcd(0x27, 16, 2);

const char* mqtt_server = "mqtt-dashboard.com";

WiFiClient espClient;

PubSubClient client(espClient);

volatile int stateCounter = 0;

volatile bool sendFlag = false;

float sharedTemp = 0, sharedHum = 0;

volatile bool dataUpdated = false;

TaskHandle_t Task0;

void Task0code(void * pvParameters) {

  for (;;) {

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

      WiFi.begin("Wokwi-GUEST", "");

      while (WiFi.status() != WL_CONNECTED) delay(500);

      Serial.println("[Core 0] WiFi Reconnected");

    }

    if (!client.connected()) {

      if (client.connect("ESP32_Button_Core0")) {

        client.subscribe("alex9ufo/DHT22");

        Serial.println("[Core 0] MQTT Connected & Subscribed to DHT22");

      }

    }

    if (sendFlag) {

      const char* cmds[] = {"on", "off", "flash", "timer"};

      const char* msg = cmds[stateCounter - 1];

      client.publish("alex9ufo/switchPB", msg);

      // 新增：顯示發行的訊息

      Serial.printf("[Core 0] ---> Published to switchPB: %s\n", msg);

      sendFlag = false;

    }

    client.loop();

    delay(10);

  }

}

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

  StaticJsonDocument<200> doc;

  deserializeJson(doc, payload, length);

  sharedTemp = doc["temp"];

  sharedHum = doc["hum"];

  dataUpdated = true;

  // 新增：顯示收到的訂閱訊息

  Serial.printf("[Core 0] <--- Received DHT22: Temp=%.1f, Hum=%.1f\n", sharedTemp, sharedHum);

}

void setup() {

  Serial.begin(115200);

  pinMode(buttonPin, INPUT);

  lcd.init();

  lcd.backlight();

  client.setServer(mqtt_server, 1883);

  client.setCallback(callback);

  xTaskCreatePinnedToCore(Task0code, "Task0", 10000, NULL, 1, &Task0, 0);

  Serial.println("System Initialized (Sender)");

}

void loop() {

  static int lastButtonState = LOW;

  int reading = digitalRead(buttonPin);

  if (reading == HIGH && lastButtonState == LOW) {

    delay(50);

    stateCounter = (stateCounter % 4) + 1;

    sendFlag = true;

    Serial.printf("[Core 1] Button Pressed. State: %d\n", stateCounter);

  }

  lastButtonState = reading;

  if (dataUpdated) {

    lcd.setCursor(0, 0);

    lcd.printf("Temp: %.1f C  ", sharedTemp);

    lcd.setCursor(0, 1);

    lcd.printf("Hum : %.1f %%  ", sharedHum);

    dataUpdated = false;

  }

  delay(10);

}

接收端：LED + DHT22 (含序列埠監控)

#include <WiFi.h>

#include <PubSubClient.h>

#include <DHT.h>

#include <ArduinoJson.h>

#define DHTPIN 15

#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);

const int ledPin = 2;

const char* mqtt_server = "mqtt-dashboard.com";

WiFiClient espClient;

PubSubClient client(espClient);

volatile int currentModeCode = 0;

unsigned long myTimerStart = 0;

float t_val = 0, h_val = 0;

TaskHandle_t Task0_Comm;

void Task0_CommCode(void * pvParameters) {

  for (;;) {

    if (!client.connected()) {

      if (client.connect("ESP32_LED_Core0")) {

        client.subscribe("alex9ufo/switchPB");

        Serial.println("[Core 0] MQTT Connected & Subscribed to switchPB");

      }

    }

    static unsigned long lastUpdate = 0;

    if (millis() - lastUpdate > 5000) { // 每5秒發行一次

      StaticJsonDocument<200> doc;

      doc["temp"] = t_val;

      doc["hum"] = h_val;

      char buffer[128];

      serializeJson(doc, buffer);

      client.publish("alex9ufo/DHT22", buffer);

      // 新增：顯示發行的訊息

      Serial.printf("[Core 0] ---> Published DHT Data: %s\n", buffer);

      lastUpdate = millis();

    }

    client.loop();

    delay(10);

  }

}

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

  String msg = "";

  for (int i = 0; i < length; i++) msg += (char)payload[i];

 

  // 新增：顯示收到的訂閱訊息

  Serial.printf("[Core 0] <--- Received switchPB: %s\n", msg.c_str());

  if (msg == "off") currentModeCode = 0;

  else if (msg == "on") currentModeCode = 1;

  else if (msg == "flash") currentModeCode = 2;

  else if (msg == "timer") {

    currentModeCode = 3;

    myTimerStart = millis();

  }

}

void setup() {

  Serial.begin(115200);

  pinMode(ledPin, OUTPUT);

  dht.begin();

  WiFi.begin("Wokwi-GUEST", "");

  while (WiFi.status() != WL_CONNECTED) delay(500);

  client.setServer(mqtt_server, 1883);

  client.setCallback(callback);

  xTaskCreatePinnedToCore(Task0_CommCode, "CommTask", 10000, NULL, 1, &Task0_Comm, 0);

  Serial.println("System Initialized (Receiver)");

}

void loop() {

  t_val = dht.readTemperature();

  h_val = dht.readHumidity();

  // 根據 currentModeCode 執行 LED 動作

  if (currentModeCode == 1) digitalWrite(ledPin, HIGH);

  else if (currentModeCode == 0) digitalWrite(ledPin, LOW);

  else if (currentModeCode == 2) digitalWrite(ledPin, (millis() / 500) % 2);

  else if (currentModeCode == 3) {

    if (millis() - myTimerStart < 5000) digitalWrite(ledPin, HIGH);

    else {

      digitalWrite(ledPin, LOW);

      currentModeCode = 0;

      Serial.println("[Core 1] Timer Finished. LED Off.");

    }

  }

  delay(100);

}