#5 2021 一起學 Raspberry Pi 4 - 溫溼度感測器DHT11由 ESP32 經 MQTT 送到 Node-RED

大家好, 今天來和大家分享如何把 DHT11溫溼度感測器上的資料由ESP32 讀取, 並用MQTT Client 發佈到 Mosquitto Server(MQTT), 再送到 Node-RED上, 再把這些資料在資訊看板上顯示出來. 

本篇使用到的程式碼:

//---- Setup update frequency -----//
const long TEMP_updateInterval = 10000; // How long to change temp and update, 10000 = 10 sec
unsigned long TEMP_currentMillis = 0;
unsigned long TEMP_previousMillis = 0; // store last time temp update

#include "DHT.h"
#define DHTPIN 23  //ESP32 pin 23
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE); // Initialize DHT sensor

/*
  SimpleMQTTClient.ino
  The purpose of this exemple is to illustrate a simple handling of MQTT and Wifi connection.
  Once it connects successfully to a Wifi network and a MQTT broker, it subscribe to a topic and send a message to it.
  It will also send a message delayed 5 seconds later.
*/

#include "EspMQTTClient.h"

EspMQTTClient client(
    "Your_WiFi_AP",     // Wi-Fi AP name
    "Wi-FI_Password", // Wi-Fi Password
    "192.168.0.119", // MQTT Broker server ip
    "",                  // Broker user name; Can be omitted if not needed
    "",                  // Broker password; Can be omitted if not needed
    "ESP32_Client",      // Client name that uniquely identify your device
    1883                 // The MQTT port, default to 1883. this line can be omitted
);

void setup()
{
    Serial.begin(115200);
    //Start DH11 sensor
    dht.begin();
    
    // Optionnal functionnalities of EspMQTTClient :
    client.enableDebuggingMessages(); // Enable debugging messages sent to serial output
    //client.enableHTTPWebUpdater();  // Enable the web updater. User and password default to values of MQTTUsername and MQTTPassword. These can be overrited with enableHTTPWebUpdater("user", "password").
    //client.enableLastWillMessage("TestClient/lastwill", "I am going offline"); // You can activate the retain flag by setting the third parameter to true
}

// This function is called once everything is connected (Wifi and MQTT)
// WARNING : YOU MUST IMPLEMENT IT IF YOU USE EspMQTTClient
void onConnectionEstablished()
{
    // Subscribe to "mytopic/test" and display received message to Serial
    client.subscribe("message/hello", [](const String &payload)
                     { Serial.println(payload); });

    // Subscribe to "mytopic/wildcardtest/#" and display received message to Serial
    //client.subscribe("mytopic/wildcardtest/#", [](const String &topic, const String &payload)
    //                 { Serial.println("(From wildcard) topic: " + topic + ", payload: " + payload); });

    // Publish a message to "mytopic/test"
    client.publish("studio/temp1", "Let's go!"); // You can activate the retain flag by setting the third parameter to true

    // Execute delayed instructions
    //client.executeDelayed(5 * 1000, []()
    //                      { client.publish("mytopic/wildcardtest/test123", "This is a message sent 5 seconds later"); });
}



void loop()
{

    TEMP_currentMillis = millis();
    if(TEMP_currentMillis - TEMP_previousMillis >= TEMP_updateInterval){
        TEMP_previousMillis = TEMP_currentMillis;

        // Reading temperature or humidity takes about 250 milliseconds!
        // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
        float humidity = dht.readHumidity();
        float temperature = dht.readTemperature();
        // Read temperature as Fahrenheit (isFahrenheit = true)
        //float f = dht.readTemperature(true);

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

        String tmp = "Current Temperature: ";
        String hud = "Current Humidity: ";
        Serial.print(tmp);
        Serial.println(String(temperature));
        Serial.print(hud);
        Serial.println(String(humidity));
        //Publish
        client.publish("studio/temp1", String(temperature));
        client.publish("studio/humd1", String(humidity));

        // Here is how to subscribe
        //client.subscribe("message/hello", [](const String &payload) { Serial.println(payload); });
    }

    client.loop();
}

*** 影片中忘了說明, 在 VS Code 裡, 按下 F1 到 Arduino Library Manager 裡, 搜尋 EspMQTTClient V.11.1版本, 並按下安裝 , 程式才能正確執行喔~~ ***

如果時間不夠的朋友, 也可以從以下的時間軸挑選想看的部份即可!

影片時間軸:

00:29 課程開始 00:52 如何將 DHT11 連接到 ESP32 (接線圖) 00:59 在 ESP32 利用 EspMQTTClient 來寫程式 01:22 安裝 DHT11 程式庫 02:16 設定 EspMQTTClient 02:45 由 Raspberry Pi Terminal 找出 Mosquitto(MQTT) IP 地址 04:51 不要用 delay() 在程式 Loop 裡！ 06:50 上傳並檢查發佈/訂閱的 messages 07:54 安裝 Node-RED 資訊看板（在 Node-RED 中） 08:57 按主題來訂閱消息 09:58 設置 MQTT 服務器的位置 11:34 建立資訊看板選項 Tabs Links & Groups 17:00 建立歷史資料資訊看板 20:32 查看資訊看板 20:50 資訊看板中的選項 Tabs Links & Groups在哪裡

下一集將介紹如何把歷史資料存儲到樹莓派的資料庫(influxDBvor MySQL)中, 以取得長時間的記錄資料. 

Stonez56 一起來學樹莓派系列影片: 

• #1 無鍵盤 無滑鼠 快速上手
  https://youtu.be/BCkdSQNtVB0 
• #2 改用 USB3/SSD 來開機, 畫面好流暢!
  https://youtu.be/uI01GFmfH1k
• #3 一行指令安裝 Node RED & 外加密碼保護       
  https://youtu.be/Mk8-xn_fHOA 
• #4 安裝 Mosquitto broker (MQTT) & 並在Node-RED & Google MQTTLens 進行測試 https://youtu.be/cK_LJPgR4mQ
• #5 溫溼度感測器DHT11由 ESP32 經 MQTT 送到 Node-RED
  https://youtu.be/Vv1JRNYIZKc 
• #6 監測資料寫入InfluxDB資料庫, 長期保存並在NodeRED資訊看板裡顯示 https://youtu.be/UOoDolPVge0 
• #7 2021 一起來學樹莓派 - 動態查詢InfluxDB 資料庫 & MQTT來遠端開/關繼電器  https://youtu.be/EpY_jl4wXtM

參考資料:

EspMQTTClient: https://github.com/plapointe6/EspMQTTClient