Create an ESP32 based smart device with Arduino and MQTT

julz — Thu, 06 Jan 2022 22:16:50 +0000

Introduction

This article will show you how to quickly create an ESP32 based "smart device", using Arduino, by creating a simple application that basically connects your WiFi router, then a MQTT server, and publishes a message every five seconds.

Of course, you can use any other WiFi enabled board.
I chose the ESP32 because I recently bought a LiliGo TTGO ESP32 board, without any specific project in mind.
This is the board I use: http://www.lilygo.cn/prod_view.aspx?Id=1126

Configuration

Board

First, we need to add support to our ESP32 board.

In the Arduino preferences, in the Additional Boards Manager URLs field, add: https://dl.espressif.com/dl/package_esp32_index.json
In the Tools menu, open the Boards Manager and look for esp32, then install it.
Still in the Tools menu, choose your board (TTGO LoRa32-OLED V1 in my case)

Libraries

In the Sketch menu, select Manage Libraries...
Install library PubSubClient

Code

Configuration

Headers

#include <WiFi.h>
#include <PubSubClient.h>

Definitions

Let's define our WiFi SSID, password, and the MQTT server
informations (hostname, port, username, password, client).

#define ssid          "MyWiFi" 
#define password      "MyWifiPassword"
#define mqtt_host     "MyMQTTServer"
#define mqtt_port     1883
#define mqtt_client   "ArduinoCl"
#define mqtt_user     "julzor"
#define mqtt_password "SomePassword"

Global variables

WiFiClient espClient;
PubSubClient cli = PubSubClient(espClient);

Connecting to WiFi

void setup_wifi()
{
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) 
  {
    delay(500);
  }
}

Connecting to MQTT

void setup_mqtt()
{
  cli.setServer(mqtt_host, mqtt_port);

  if (cli.connect(mqtt_client, mqtt_user, mqtt_password))
  {
    // Now we're connected to the MQTT server
    // Let's publish a first message...
    cli.publish("test/hello", "hello world");
  }
}

Putting it all together

Setup

void setup()
{
    Serial.begin(115200);

    delay(10);

    setup_wifi();
    setup_mqtt();
}

Loop

long last = 0;

void loop() {
  if (!cli.connected())
  {
    // We were disconnected, let's reconnect
    delay(1000);
    setup_mqtt();
  }
  else
  {
    cli.loop();

    long now = millis();
    if (now - last > 5000)
    {
      last = now;
      cli.publish("test/ping", "Ping");
    }
  }
}

Conclusion

You should now have a working application that does nothing but send a ping message on your MQTT server. That's a start!

In another article, I will show you how I use my useless smart device with Node-RED, a Raspberry Pi, and Alexa.

DEV Community: julz

Create an ESP32 based smart device with Arduino and MQTT

Introduction

Configuration

Board

Libraries

Code

Configuration

Headers

Definitions

Global variables

Connecting to WiFi

Connecting to MQTT

Putting it all together

Setup

Loop

Conclusion