442.ESP8266 in conjunction with Node-RED and MQTT In this post, we are going to demonstrate how you can use Node-RED to control the outputs of an ESP8266 and display sensor data received from an ESP8266. The Node-RED software is being run on a Raspberry Pi, and the MQTT communication protocol is being used to facilitate communication between the ESP8266 and the Node-RED software. Node-RED and Node-RED Dashboard It is necessary for your Raspberry Pi to have Node-RED and the Node-RED Dashboard application installed. The blog posts listed below are helpful if you are just getting started with Node-RED and the Node-RED dashboard: MQTT Protocol

Using MQTT, we are going to connect an ESP8266 to a Raspberry Pi that is operating the Node-RED software. The goal of this tutorial is to enable two- way communication between the two devices. MQTT is an acronym that stands for " MQ Telemetry Transport." It describes a system that allows clients to both send and receive messages, and it is a nice, lightweight publish and subscribe system. It is a straightforward messaging protocol that was developed for devices that have limited resources and bandwidth. Therefore, it is an ideal option for use in applications related to the Internet of Things. Installing Mosquitto Broker In MQTT, it is the broker's primary responsibility to receive all messages, filter those messages, determine which clients are interested in a particular message, and then publish that message to all clients who have subscribed to it. There are many different brokers available for your use. In this guide, we are going to make use of the Mosquitto Broker, which requires the Raspberry Pi to have the appropriate software installed.

Execute the following command to determine whether or not the Mosquitto

pi@raspberry:~ $ mosquitto -v This gives you the version of Mosquitto that is currently installed and operating on your Raspberry Pi. It should be 1.4 or higher at the very least. Note that in addition to returning the Mosquitto version that is currently installed, the Mosquitto command attempts to initialize Mosquitto once

more. Due to the fact that Mosquitto is already active, an error message is displayed. If you see a message like this, you don't need to worry because Mosquitto has been installed and is running correctly. Establishing a MQTT communication with Node-RED Using the Node-RED nodes, we are going to set up a communication using the MQTT protocol in this section. Dashboard Layout The first thing you need to do is design the layout for the dashboard. In this demonstration, we will make use of a button to control an ESP8266 output, as well as a chart and a gauge to display the temperature and humidity readings collected by the DHT11 sensor. Choose the Layout tab from the drop-down menu that appears after you click the dashboard tab in the Node-RED window's upper right corner. Make a tab labeled Room, and then inside that tab, make two groups: one labeled Lamp, and the other labeled Sensor. Preparing your Arduino IDE We will use the Arduino IDE to write the code for the ESP8266. In order to use the Arduino Integrated Development Environment (IDE) to upload code to your ESP8266, you will need to install the ESP8266 add-on (How to Install the ESP8266 Board in Arduino IDE). In order for everything to be prepared for your ESP8266, you will additionally need to install two additional libraries. Installing the PubSubClient Library A client for performing straightforward publish/subscribe messaging with a server that supports the MQTT protocol is made available by the

PubSubClient library (basically allows your ESP8266 to talk with Node- RED). 1. Save the PubSubClient library to your computer. Within your Downloads folder, there should be a folder labeled ".zip." 2. After you have unzipped the.zip folder, you should see a folder named pubsubclient-master. 3. Rename your folder's current name, which is pubsubclient-master, to just pubsubclient. 4. Transfer the pubsubclient folder to the libraries folder that was created during the installation of your Arduino IDE. 5. Next, reopen the Arduino IDE on your computer. The library includes several different examples in the form of sketches. Within the Arduino IDE software, navigate to the File > Examples > PubSubClient menu option. Installing Support for DHT Sensors in the Library Your ESP8266 or Arduino boards will be able to read temperature and humidity with ease when you use the DHT sensor library. This library makes it simple to use any DHT sensor. 1. Save the DHT sensor library to your computer. Within your Downloads folder, you ought to have a.zip folder. 2. After you have unzipped the.zip folder, you should have access to the DHT-sensor-library-master folder. 3. Rename your folder's current name, which is DHT-sensor-library- master, to simply DHT. 4. Transfer the DHT folder to the libraries folder that was created during the installation of your Arduino IDE. 5. Once you have done that, reopen your Arduino IDE.

Selecting the right board on Arduino IDE You also need to make sure that you select the appropriate board when using

1. Navigate to the Tools menu and select "NodeMCU 1.0 (ESP-12E Module)" from the drop-down menu. 2. Under Tools > Port > COM4, choose the port number that corresponds to your ESP (in my case) Uploading code You are now able to upload the code that is listed below to your ESP8266. This piece of code publishes messages containing the temperature and humidity from the DHT11 sensor on the room/temperature and room/humidity topics using the MQTT protocol. The room/lamp topic is subscribed to by the ESP so that it can receive the messages that are published on that topic by the Node- RED application. These messages contain instructions for turning the lamp on and off. The areas of the code that require modifications have detailed comments attached to them. It is necessary for you to edit the code to include your personal RPi IP address, SSID, and password. This code is also compatible with other DHT sensors; all you need to do to select the appropriate sensor for your application is uncomment and comment the appropriate lines of code.

After you have uploaded the code and ensured that your Node-RED application and the Mosquito broker are both running on the Raspberry Pi, you can open the serial monitor in the Arduino IDE and set the baud rate to 115200 in order to view the events as they occur in real time. This is a useful method for determining whether or not the ESP has successfully established a connection to both your router and the Mosquito broker. You are also able to view the messages that the ESP is publishing as well as receiving. Building the Circuit The components and diagrams of the circuit that you will need to construct for this project are presented in the following sections.

To construct the circuit, you will need the following components Raspberry Pi ESP8266 (ESP-12E Nodemcu) DHT11 temperature and humidity sensor Breadboard resistors 330 ohm and 4700-ohm LED resistor

Congratulations! The work on your project is now finished. To control the ESP using the Node-RED application, navigate to the http://your-pi-ip- address/ui website address. You are able to use any web browser, as long as it is connected to the same network as your Raspberry Pi. The application should look something the figure below.

In this project, we showed you how to use Node-RED and MQTT to control ESP lights and sensors. You can construct more complex projects by building on top of these fundamental steps.