Arduino ide + esp8266+mqtt subscribe to publish temperature and humidity information

1、 Library file installation

（1） Install first ESP8266 Support

file -> Preferences -> Add development board manager address
add to http://arduino.esp8266.com/stable/package_esp8266com_index.json

（2） Click Tools - Development board - Development board Manager , Enter the development board manager interface ： find esp8266 And install ;
（3） Tools -> Development board -. The selection is as follows

（4） Download the external library package

Address ： https://github.com/JINYU-ZHOU/MQTT-DHT11.git（ If you have any other questions, please leave a message ）

Point item -> Load the library -> add to .zip library -> Select the compressed package you downloaded , The following window will prompt you whether to install the results ！

2、ESP8266 Distribution network

I have read many tutorials of distribution network , I think PubSubClient Library instances are particularly compatible ,. This library can be found in Arduino IDE Found in the library manager of . Tools -> Management of the library -> find PubSubClient Download according to the version you want , Then open the instance
You just need to add the name and password of the network you want to connect to, and you want to connect to MQTT The address of the server

const char* ssid = "........";// Yours WIFI name 
const char* password = "........";// Yours WIFI password 
const char* mqtt_server = "broker.mqtt-dashboard.com";
// You want to connect MQTT Server address, such as const char* mqtt_server = "123.57.133.11";

After connecting to the network successfully, the serial port will prompt

*

If you don't use it indirectly Arduino, Direct connection ESP8266, Need to download ahead of time CH340 perhaps CP2102 The driver ,
I am using CP2102, If you need to leave a message, I will email you .

3、 Temperature and humidity module test

Prerequisite Download DHT11 Corresponding library package , The same address as above . This is the source code , It is only used to test the temperature and humidity module , Subsequent subscriptions also need to be assembled .

#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、 Subscribe and publish information

In my previous blog post, I mentioned subscription and release code , If you want to learn more, you can click MQTT+ardunio+ESP8266 Development
Part of the code for simply releasing information is as follows , Refer to my previous blog for all the codes .

void loop() {
    

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

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

This time we need to snprintf (msg, 75, "hello world #%ld", value); In the middle of the hello world #%ld Replace with our temperature and humidity data
Can you do this directly ？

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);
}

If you upload directly in this way, an error will be reported ！！！ You can learn snprintf This function , The third variable is const char
So there's a good way , Change your temperature and humidity data into a string

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

We make use of string Function to convert a string to const char type

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

The total code is attached at the end

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#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、 Experimental results

Welcome criticism , I'm also a beginner , Record every simple progress .
I would like to thank the seniors and classmates who helped me ！
I hope to become a little attendant of the big guy as soon as possible ~