Arduino IDE + ESP8266+MQTT订阅发布温湿度信息

1、库文件安装

（1）先安装ESP8266支持

文件->首选项->附加开发板管理器地址
添加http://arduino.esp8266.com/stable/package_esp8266com_index.json

（2）点击工具 - 开发板 - 开发板管理器，进入开发板管理器界面：找到 esp8266 并安装；
（3）工具->开发板-。选择如下图

（4）下载外库包

地址： https://github.com/JINYU-ZHOU/MQTT-DHT11.git（如果有其他问题欢迎留言）

点项目->加载库->添加.zip库->选择你下载好的压缩包，下面窗口回提示你是否安装成果！

2、ESP8266配网

看了很多配网的教程，我觉得PubSubClient库实例特别兼容，. 此库可以在Arduino IDE的库管理器中找到。工具->管理库->找到PubSubClient根据自己想要的版本下载，之后打开实例
你只需加上自己要连接网的名字和密码以及你要连接MQTT服务器的地址

const char* ssid = "........";//你的WIFI名称
const char* password = "........";//你的WIFI密码
const char* mqtt_server = "broker.mqtt-dashboard.com";
//你要连接的MQTT服务器地址如const char* mqtt_server = "123.57.133.11";

连接网络成功后串口会提示

*

如果你不间接使用Arduino，直接连接ESP8266，需要提前下载CH340或者CP2102的驱动，
我用的CP2102，如果需要可以留言我发邮箱。

3、温湿度模块测试

前提下载DHT11相应的库包，还是上面那个地址。这是源代码，只是单单用来测试温湿度模块，后续订阅还需要进行组装。

#include "DHT.h"
#define DHTPIN 5
#define DHTTYPE DHT11

// Initialize DHT sensor
DHT dht(DHTPIN, DHTTYPE, 15);

void setup() {
     

  // Start Serial  
  Serial.begin(115200); 
 
  // Init DHT 
  dht.begin();
}

void loop() {
     

  // Reading temperature and humidity
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // Display data
  Serial.print("Humidity: "); 
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: "); 
  Serial.print(t);
  Serial.println(" *C ");
  
   // Wait a few seconds between measurements.
  delay(2000);
}

4、订阅加发布信息

我之前的博文有提过订阅加发布代码，如果想了解更多可以点击MQTT+ardunio+ESP8266开发
简单发布信息的部分代码如下，全部代码参考我之前的博文。

void loop() {
     

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

  long now = millis();
  if (now - lastMsg > 20000) {
     //延时
    lastMsg = now;
    ++value;
    snprintf (msg, 75, "hello world #%ld", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }

这次需要将snprintf (msg, 75, "hello world #%ld", value);中间的hello world #%ld替换成我们的温湿度数据
能直接这样吗？

void loop() {
     

  // Reading temperature and humidity
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  void loop() {
     
    ...
    snprintf (msg, 75, h, value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }
   // Wait a few seconds between measurements.
  delay(2000);
}

如果这样直接上传就会报错！！！可以了解snprintf这个函数，第三个变量为const char
那么有个好方法，把你的温湿度数据变成字符串

String data = "{\"H\":" + String(h) +",\"T\":" + String(t)+"}";

我们利用string函数将字符串转换为const char 类型

strcpy(c,data.c_str());//char c[50];

最后附上总代码

#include 
#include 
#include "DHT.h"
#define DHTPIN 5
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE, 15);
// Update these with values suitable for your network.

const char* ssid = "JINYU";
const char* password = "150";
const char* mqtt_server = "123.57.133.11";

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup() {
     
  pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
  Serial.begin(115200);
  dht.begin();
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

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* 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();

  // 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 acive 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.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP8266Client")) {
     
      Serial.println("connected");
      // Once connected, publish an announcement...
      client.publish("outTopic", "hello world");
      // ... and resubscribe
      client.subscribe("inTopic");
    } 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() {
     
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  char c[50];

  // Display data
  Serial.print("Humidity: "); 
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: "); 
  Serial.print(t);
  Serial.println(" *C ");
   // Wait a few seconds between measurements.
  delay(2000);

String data =String(h) +"," + String(t) ;
strcpy(c,data.c_str());
  if (!client.connected()) {
     
    reconnect();
  }
  client.loop();

  long now = millis();
  if (now - lastMsg > 2000) {
     
    lastMsg = now;
    ++value;
    snprintf (msg, 75, c, value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }
}

5、实验结果图

欢迎大家批评指正，我也是初学者，记录每一次简单的进步。
特此感谢为我提供帮助的学长们和同学！
希望早日成为大佬的小跟班~