NodeMCU and MQTT Protocol

Introduction to MQTT Protocol and code to demonstrate its working

Overview :
This repository gives the basics of MQTT Protocol in a way easily understandable by a beginner. It also contains a small demo code for using MQTT with Adafruit IO and NodeMCU-ESP8266.

About MQTT :
MQTT is a light weight Publish and Subscribe Protocol that provides for a two way communication between the IoT device and the MQTT Hosting Server. There is a feed of data that is being sent and received by devices. All the devices that are Subscribed to that particluar stream will recieve the value in case the server sends any data into the stream. In a similar fashion, All the devices that can Publish to a stream will keep posting new data to the feed, which will now be received by all the devices that are subscribed.

The main components of MQTT Protocol :

• MQTT Client - The device that either can either publish/subscribe to the feed.
• MQTT Broker - The server which hosts the MQTT Dashboard

Popular IoT cloud dashboard providers like Adafruit IO, Blynk, Arduino Cloud, etc. have support for MQTT Protocol in their services. Let's now dive deep into using the MQTT Protocol using NodeMCU Development Board.

Demo code for MQTT Protocol using Adafruit IO

Components Required :

• NodeMCU-ESP8266 - Any generic NodeMCU would do just fine
• LED - any colour
• Breadbaord and Jumper Wires (Male to Female)

Software Requirements :

• Arduino IDE (Download)
• Adafruit IO (Register)

Getting Started with NodeMCU :
Refer to my other repository (this one) in case you need to learn the very basics of NodeMCU. Once you get a basic understanding of how a NodeMCU works, and are comfortable with the coding part, then proceed further with setting up the Arduino IDE.

Setting up the Arduino IDE Environment :
A few additional libraries are required in order to work with MQTT and Adafruit IO. Install all the assiciated dependencies along with the main libraries. Refer this link for a clear step by step guide in installing these libraries. Below is the list of all the required libraries.

• Adafruit IO Arduino by Adafruit
• Adafruit MQTT Library by Adafruit
• ArduinoHttpClient by Arduino

Setting up the Adafruit IO Dashboard :

• Once you register in the Adafruit IO website, head over to the Feeds subsection.
• Click on the New Feed button. Name the feed as LEDbutton. Now click on the Create button.
• Once done, head over to the Dashboards section and click on the New Dashboard option.
• Name the dashboard and select Create.
• Once done, open the newly created dashboard. Select the small gear icon on the top right, and select Create New Block option.
• From the new window, select the "On-Off buttion" block.
• Select the previously created feed, and go to the next step.
• Assign 0 for OFF and 1 for ON and create the block.

Coding the NodeMCU :
Now in the Arduino IDE, go to File -> Examples -> Arduino MQTT Library -> mqtt_esp8266. A few changes are required in the code for controlling the LED. Check the Code folder to find the full updated code.

Connections :

(Done using Fritzing)

In the code, enter your WiFi details in the WLAN_SSID, and WLAN_PASS section. AIO_USERNAME and AIO_KEY can be found from the Adafruit IO Dashboard. Click on the Key Icon on the top right corner to view the Username and Key.

Compile and upload the code to your NodeMCU. Once done, check the Serial monitor for the connection status. You can now control the LED on NodeMCU using the switch on Adafruit IO Dashboard.

Versions :

• v1.0.0 - Original prototype version by Bharadwaj Routhu using Adafruit IO and NodeMCU

And That's It!
You've now learnt the basics of MQTT protocol using NodeMCU and Adafruit IO Dashboard. If you like this project, please star the repository. Visit my GitHub Profile for many such projects on IoT, Cloud Computing, and other Embedded Development boards.