ESP8266 and Node-RED with MQTT (Publish and Subscribe)

In this post we’re going to show you how to control ESP8266 outputs and display sensor data from the ESP8266 on Node-RED. The Node-RED software is running on a Raspberry Pi, and the communication between the ESP8266 and the Node-RED software is achieved with the MQTT communication protocol.

The following figure shows an overview of what we’re going to do in this tutorial.

First, watch the video demonstration below

Node-RED and Node-RED Dashboard

You need to have Node-RED and Node-RED Dashboard installed in your Raspberry Pi. The following blog posts are useful for getting started with Node-RED and Node-RED dashboard:

MQTT Protocol

In this tutorial we’re going to establish a communication between a Raspberry Pi running the Node-RED software and an ESP8266 using MQTT.

MQTT stands for MQ Telemetry Transport and it is a nice lightweight publish and subscribe system where you can publish and receive messages as a client. It is a simple messaging protocol, designed for constrained devices and with low-bandwidth. So, it’s the perfect solution for Internet of Things applications.

If you want to learn more about MQTT, watch the video below.

For a written version of this video and additional resources, read this blog post What is MQTT and How It Works.

Installing Mosquitto Broker

In MQTT, the broker is primarily responsible for receiving all messages, filtering the messages, decide who is interested in it and then publishing the message to all subscribed clients.

There are several brokers you can use. In this tutorial we’re going to use the Mosquitto Broker which needs to be installed on Raspberry Pi.

DOWNLOAD FREE PDF: ESP8266 Web Server with Arduino IDE

To install the Mosquitto broker on Raspberry pi follow the next steps.

For additional information you can read How to Install Mosquitto Broker on Raspberry Pi.

Updating the repository

To update the repository you need to import the repository package signing key:

pi@raspberry:~ $ wget http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key
pi@raspberry:~ $ sudo apt-key add mosquitto-repo.gpg.key

Make the repository available to be installed with apt:

pi@raspberry:~ $ cd /etc/apt/sources.list.d/
pi@raspberrypi:/etc/apt/sources.list.d $

Then, run the following command:

pi@raspberrypi:/etc/apt/sources.list.d $ sudo wget http://repo.mosquitto.org/debian/mosquitto-jessie.list

Go back to the root directory:

pi@raspberrypi:/etc/apt/sources.list.d $ cd
pi@raspberry:~ $

Finally, update apt information:

pi@raspberry:~ $ sudo apt update

Installing

To install the Mosquitto broker and make it auto start enter the following command:

pi@raspberry:~ $ sudo apt install mosquitto
pi@raspberry:~ $ sudo systemctl enable mosquitto.service

You need to type Y and press Enter to confirm the installation.

Testing

To see if Mosquitto broker was successfully installed, send the following command:

pi@raspberry:~ $ mosquitto -v

This returns the Mosquitto version that is currently running in your Raspberry Pi. It should be 1.4 or above.

Note: the Mosquitto command returns the Mosquitto version that is currently installed, but it also tries to initialize Mosquitto again. Since Mosquitto is already running it prompts an error message. Don’t worry Mosquitto is properly installed and running if you see a similar message.

Establishing an MQTT communication with Node-RED

In this section we’re going to establish an MQTT communication using the Node-RED nodes.

Dashboard Layout

The first step is to create the dashboard layout. In this example, we’ll have a button to control an ESP8266 output; a chart and a gauge to display temperature and humidity readings from the DHT11 sensor.

On the top right corner of the Node-RED window, select the Layout tab under the dashboard tab. Create a tab called Room and inside the Room tab, create two groups: Lamp and Sensor as shown in figure below.

Creating the Flow

Drag the following nodes to the flow – see figure below:

switch – this will control the ESP8266 output
mqtt output node – this will publish a message to the ESP8266 accordingly to the switch state
2x mqtt input nodes – this nodes will be subscribed to the temperature and humidity topics to receive sensor data from the ESP
chart – will display the temperature sensor readings
gauge – will display the humidity sensor readings

Node-RED and the MQTT broker need to be connected. To connect the MQTT broker to Node-REd, double-click the MQTT output node. A new window pops up – as shown in figure below.

Click the Add new mqtt-broker option.
Type localhost in the server field
All the other settings are configured properly by default.
Press Add and the MQTT output node automatically connects to your broker.

Edit all the other nodes properties as shown in the following figures:

switch – the switch sends an on string message when it’s on; and sends an off string message when it’s off. This node will publish on the room/lamp topic. Your ESP will then be subscribed to this topic, to receive its messages.
mqtt output node. This node is connected to the mosquitto broker and it will publish in the room/lamp topic.
mqtt input node. This node is subscribed to the room/temperature topic to receive temperature sensor data from the ESP8266. The ESP8266 will be pusblishing the temperature readings on this topic.
chart. The chart will display the readings received on the room/temperature topic.
mqtt input node. This node is subscribed to the room/humidity topic to receive humidity sensor data from the ESP8266. The ESP8266 will be pusblishing the humidity readings on this same topic.
gauge. The gauge will display the readings received on the room/humidity topic.

Wire your nodes as shown in the figure below.

Your Node-RED application is ready. Click the Deploy button on the top right corner.

The Node-RED application is ready. To see how your dashboard looks go to http://your-pi-ip-address/ui.

Now, follow the next sections to prepare your ESP8266.

Preparing your Arduino IDE

We’ll program the ESP8266 using the Arduino IDE. In order to upload code to your ESP8266 using the Arduino IDE, you need to install the ESP8266 add-on (How to Install the ESP8266 Board in Arduino IDE). You’ll also need to install two additional libraries to have everything ready for your ESP8266.

Installing the PubSubClient Library

The PubSubClient library provides a client for doing simple publish/subscribe messaging with a server that supports MQTT (basically allows your ESP8266 to talk with Node-RED).

1) Click here to download the PubSubClient library. You should have a .zip folder in your Downloads folder

2) Unzip the .zip folder and you should get pubsubclient-master folder

3) Rename your folder from ~~pubsubclient-master~~ to pubsubclient

4) Move the pubsubclient folder to your Arduino IDE installation libraries folder

5) Then, re-open your Arduino IDE

The library comes with a number of example sketches. See File >Examples > PubSubClient within the Arduino IDE software.

Installing the DHT Sensor Library

The DHT sensor library provides an easy way of using any DHT sensor to read temperature and humidity with your ESP8266 or Arduino boards.

1) Click here to download the DHT sensor library. You should have a .zip folder in your Downloads

2) Unzip the .zip folder and you should get DHT-sensor-library-master folder

3) Rename your folder from ~~DHT-sensor-library-master~~ to DHT

4) Move the DHT folder to your Arduino IDE installation libraries folder

5) Then re-open your Arduino IDE

For more information about the DHT11 sensor and the ESP8266, read ESP8266 DHT11/DHT22 Temperature and Humidity Web Server with Arduino IDE.

Selecting the right board on Arduino IDE

You also need to select the right board on Arduino IDE:

1) Go to Tools and select “NodeMCU 1.0 (ESP-12E Module)”.

2) Select your ESP port number under the Tools > Port > COM4 (in my case)

Uploading code

Now, you can upload the following code to your ESP8266. This code publishes messages of the temperature and humidity from the DHT11 sensor on the room/temperature and room/humidity topics trough MQTT protocol.

The ESP is subscribed to the room/lamp topic to receive the messages published on that topic by the Node-RED application, to turn the lamp on or off.

The code is well commented on where you need to make changes. You need to edit the code with your own SSID, password and RPi IP address.

This code is also compatible with other DHT sensors – you just need to uncomment and comment the right lines of code to chose your sensor.

/*****
 
 All the resources for this project:
 http://randomnerdtutorials.com/
 
*****/
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include "DHT.h"
// Uncomment one of the lines bellow for whatever DHT sensor type you're using!
#define DHTTYPE DHT11   // DHT 11
//#define DHTTYPE DHT21   // DHT 21 (AM2301)
//#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
// Change the credentials below, so your ESP8266 connects to your router
const char* ssid = "REPLACE_WITH_YOUR_SSID";
const char* password = "REPLACE_WITH_YOUR_PASSWORD";
// Change the variable to your Raspberry Pi IP address, so it connects to your MQTT broker
const char* mqtt_server = "REPLACE_WITH_YOUR_RPI_IP_ADDRESS";
// Initializes the espClient. You should change the espClient name if you have multiple ESPs running in your home automation system
WiFiClient espClient;
PubSubClient client(espClient);
// DHT Sensor - GPIO 5 = D1 on ESP-12E NodeMCU board
const int DHTPin = 5;
// Lamp - LED - GPIO 4 = D2 on ESP-12E NodeMCU board
const int lamp = 4;
// Initialize DHT sensor.
DHT dht(DHTPin, DHTTYPE);
// Timers auxiliar variables
long now = millis();
long lastMeasure = 0;
// Don't change the function below. This functions connects your ESP8266 to your router
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.print("WiFi connected - ESP IP address: ");
  Serial.println(WiFi.localIP());
}
// This functions is executed when some device publishes a message to a topic that your ESP8266 is subscribed to
// Change the function below to add logic to your program, so when a device publishes a message to a topic that 
// your ESP8266 is subscribed you can actually do something
void callback(String topic, byte* message, unsigned int length) {
  Serial.print("Message arrived on topic: ");
  Serial.print(topic);
  Serial.print(". Message: ");
  String messageTemp;
  
  for (int i = 0; i < length; i++) {
    Serial.print((char)message[i]);
    messageTemp += (char)message[i];
  }
  Serial.println();

  // Feel free to add more if statements to control more GPIOs with MQTT

  // If a message is received on the topic room/lamp, you check if the message is either on or off. Turns the lamp GPIO according to the message
  if(topic=="room/lamp"){
      Serial.print("Changing Room lamp to ");
      if(messageTemp == "on"){
        digitalWrite(lamp, HIGH);
        Serial.print("On");
      }
      else if(messageTemp == "off"){
        digitalWrite(lamp, LOW);
        Serial.print("Off");
      }
  }
  Serial.println();
}
// This functions reconnects your ESP8266 to your MQTT broker
// Change the function below if you want to subscribe to more topics with your ESP8266 
void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    /*
     YOU MIGHT NEED TO CHANGE THIS LINE, IF YOU'RE HAVING PROBLEMS WITH MQTT MULTIPLE CONNECTIONS
     To change the ESP device ID, you will have to give a new name to the ESP8266.
     Here's how it looks:
       if (client.connect("ESP8266Client")) {
     You can do it like this:
       if (client.connect("ESP1_Office")) {
     Then, for the other ESP:
       if (client.connect("ESP2_Garage")) {
      That should solve your MQTT multiple connections problem
    */
    if (client.connect("ESP8266Client")) {
      Serial.println("connected");  
      // Subscribe or resubscribe to a topic
      // You can subscribe to more topics (to control more LEDs in this example)
      client.subscribe("room/lamp");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}
// The setup function sets your ESP GPIOs to Outputs, starts the serial communication at a baud rate of 115200
// Sets your mqtt broker and sets the callback function
// The callback function is what receives messages and actually controls the LEDs
void setup() {
  pinMode(lamp, OUTPUT);
  
  dht.begin();
  
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}
// For this project, you don't need to change anything in the loop function. Basically it ensures that you ESP is connected to your broker
void loop() {

  if (!client.connected()) {
    reconnect();
  }
  if(!client.loop())
    client.connect("ESP8266Client");

  now = millis();
  // Publishes new temperature and humidity every 30 seconds
  if (now - lastMeasure > 30000) {
    lastMeasure = now;
    // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
    float h = dht.readHumidity();
    // Read temperature as Celsius (the default)
    float t = 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(h) || isnan(t) || isnan(f)) {
      Serial.println("Failed to read from DHT sensor!");
      return;
    }

    // Computes temperature values in Celsius
    float hic = dht.computeHeatIndex(t, h, false);
    static char temperatureTemp[7];
    dtostrf(hic, 6, 2, temperatureTemp);
    
    // Uncomment to compute temperature values in Fahrenheit 
    // float hif = dht.computeHeatIndex(f, h);
    // static char temperatureTemp[7];
    // dtostrf(hic, 6, 2, temperatureTemp);
    
    static char humidityTemp[7];
    dtostrf(h, 6, 2, humidityTemp);

    // Publishes Temperature and Humidity values
    client.publish("room/temperature", temperatureTemp);
    client.publish("room/humidity", humidityTemp);
    
    Serial.print("Humidity: ");
    Serial.print(h);
    Serial.print(" %\t Temperature: ");
    Serial.print(t);
    Serial.print(" *C ");
    Serial.print(f);
    Serial.print(" *F\t Heat index: ");
    Serial.print(hic);
    Serial.println(" *C ");
    // Serial.print(hif);
    // Serial.println(" *F");
  }
} 

view rawProjects/ESP8266_NodeRED_MQTT_LED_DHT.ino

After uploading the code, and with the Raspberry Pi running your Node-RED application and the Mosquitto broker, you can open the Arduino IDE serial monitor at a baud rate of 115200 and see what’s happening in real time.

This is helpful to check if the ESP has established a successful connection to your router and to the Mosquitto broker. You can also see the messages the ESP is receiving and publishing.

Building the Circuit

The following sections show you the needed parts and schematics to build the circuit for this project.

Parts required

These are the parts required to build the circuit (click the links below to find the best price at Maker Advisor):

You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!

Schematics

Here are the schematics for this project’s circuit.

Demonstration

Congratulations! You project is now completed.

Go to http://your-pi-ip-address/ui to control the ESP with the Node-RED application. You can access your application in any browser on the same network that your Pi (watch the video demonstration below).

The application should look something the figure below.

Wrapping up

In this tutorial we’ve shown you the basic concepts that will allow you to turn on lights and monitor sensors on your ESP using Node-RED and the MQTT communication protocol. You can follow these basic steps to build more advanced projects.

We hope you’ve found this tutorial useful.

If you liked this project and Home Automation make sure you check our course: Build a Home Automation System for $100.

alex9ufo 聰明人求知心切

2018年3月10日星期六