Arduino #32 用一塊ESP32來學 IOT (#32 Learn IOT with MQTT + ESP32)

大家好, 今天和大家來分享, Arduino #32 用一塊ESP32來學 IOT (#32 Learn IOT with MQTT + ESP32) 這個影片很適合初學者來觀看學習. 影片內容主要是告訴大家, 只要手上有一塊 ESP32 和一台電腦, 就可以開始學習 IOT 了 ! 看過這個影片, 你會了解學習 IOT 一點都不難喔! 甚至可以延伸作法, 利用 MQTTlens 透過雲端EMQX來做遠端的控制!

參考資料:

• Pubsubclient library: https://github.com/knolleary/pubsubclient/blob/master/examples/mqtt_esp8266/mqtt_esp8266.ino
• Additional Boards Manager URL: https://arduino.esp8266.com/stable/package_esp8266com_index.json,https://dl.espressif.com/dl/package_esp32_index.json
• Source code: https://stonez56.blogspot.com/

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：

• 00:00 開始
• 00:29 什麼是 MQTT，它是如何運作的？
• 01:30 你的第一個IOT專案！
• 01:55 MQTT 程式：pubsubclient
• 02:40 Arduino IDE: 設定Additional Boards Manager URL
• 03:09 Arduino IDE 其它設定
• 03:48 從我的部落格中下載程式並貼在Arduino IDE
• 04:07 在程式中更改必要的設定
• 07:27 從 Chrome 瀏覽器啟動 MQTTlens
• 07:54 在 MQTTlens 新增 EMQX 連線
• 09:54 訂閱 ESP32上的兩個主題
• 11:19 從 MQTTlens 發布主題
• 12:45 本次主要內容摘要

程式碼:

/*
 Basic ESP8266 MQTT example
 This sketch demonstrates the capabilities of the pubsub library in combination
 with the ESP8266 board/library.
 It connects to an MQTT server then:
  - publishes "hello world" to the topic "outTopic" every two seconds
  - subscribes to the topic "inTopic", printing out any messages
    it receives. NB - it assumes the received payloads are strings not binary
  - If the first character of the topic "inTopic" is an 1, switch ON the ESP Led,
    else switch it off
 It will reconnect to the server if the connection is lost using a blocking
 reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
 achieve the same result without blocking the main loop.
 To install the ESP8266 board, (using Arduino 1.6.4+):
  - Add the following 3rd party board manager under "File -> Preferences -> Additional Boards Manager URLs":
       http://arduino.esp8266.com/stable/package_esp8266com_index.json
  - Open the "Tools -> Board -> Board Manager" and click install for the ESP8266"
  - Select your ESP8266 in "Tools -> Board"
*/
 
#include <WiFi.h>
#include <PubSubClient.h>
#include <EasyButton.h>
#define LED 2        //built-in LED on ESP32
 
// Update these with values suitable for your network.
const char *ssid = "WiFi-SSID";
const char *password = "WiFi-PASSWORD";
 
// Define your client ID on EMQX
String mqtt_ClientID = "stonez56_IOT_Station_";
 
// Define your topics to subscribe / publish
const char* sub_topic = "stonez56/esp32s";
const char* pub_led_topic = "stonez56/esp32s_led_state";
const char* pub_init_topic = "stonez56/esp32s_is_back";
 
// EMQX broker parameters
const char *mqtt_server = "broker.emqx.io";
const char *mqtt_userName = "emqx";
const char *mqtt_password = "public";
 
WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE (50)
char msg[MSG_BUFFER_SIZE];
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("] ");
    for (int i = 0; i < length; i++)
    {
        Serial.print((char)payload[i]);
    }
    Serial.println();
 
    payload[length] = '\0';
    String message = (char *)payload;
    
    if (strcmp(topic, sub_topic) == 0)
    {
        if (message == "off")
        {
            digitalWrite(LED, LOW); //Turn off
            client.publish(pub_led_topic, "off");
        }
        if (message == "on")
        {
            digitalWrite(LED, HIGH); //Turn on
            client.publish(pub_led_topic, "on");
        }
    }
 
    /* Switch on the LED if an 1 was received as first character
    // if ((char)payload[0] == '1')
    // {
    //     digitalWrite(BUILTIN_LED, LOW); // Turn the LED on (Note that LOW is the voltage level
    //                                     // but actually the LED is on; this is because
    //                                     // it is active low on the ESP-01)
    // }
    // else
    // {
    //     digitalWrite(BUILTIN_LED, HIGH); // Turn the LED off by making the voltage HIGH
    // } */
}
 
void reconnect()
{
    // Loop until we're reconnected
    while (!client.connected())
    {
 
        Serial.println("Attempting EMQX MQTT connection...");
        // Create a random client ID
        mqtt_ClientID += String(random(0xffff), HEX);
        // Attempt to connect
        if (client.connect((mqtt_ClientID, mqtt_userName, mqtt_password)))
        {
            Serial.print(" connected with Client ID: ");
            Serial.println(mqtt_ClientID);
            // Once connected, publish an announcement...
            client.publish(pub_init_topic, "Hi, I'm online!");
            // ... and resubscribe
            client.subscribe(sub_topic);
        }
        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, OUTPUT); // Initialize the _LED pin as an output
    digitalWrite(LED, LOW); //default ESP32 LOW is turn off
 
    Serial.begin(115200);
    setup_wifi();
    client.setServer(mqtt_server, 1883);
    client.setCallback(callback);
}
 
void loop()
{
 
    if (!client.connected())
    {
        reconnect();
    }
    client.loop();
 
    /* unsigned long now = millis();
    // if (now - lastMsg > 2000)
    // {
    //     lastMsg = now;
    //     ++value;
    //     snprintf(msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
    //     Serial.print("Publish message: ");
    //     Serial.println(msg);
    //     client.publish("stonez56/esp32s_button_pushed", msg);
    // } */
}