MQTT Ethernet using Arduino UNO

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In this post we’re going to show you example of publish and subscribe with MQTT Ethernet using Arduino UNO board testing with NodeRed.

The communication between NodeRed and Arduino UNO with the help of MQTT communication protocol.

Table of Contents

Schematic Overview

The following figure shows wire connection and overview of this project,

Parts Required

For this tutorial, you need the following parts:

Arduino UNO Development board
Ethernet Module (ENC80J60)
Jumper Wires
Breadboard

If you want to learn more about MQTT, then see the blog post below:

Installing Libraries

Installing the PubSubClient Library

Click here to download the PubSubClient Library. You should have a .zip folder in your Downloads folder.
You can go to Sketch > Include Library > Add. ZIP library and select the library you’ve just downloaded.

Installing the EthernetENC Library

Click here to download the EthernetENC Library. You should have a .zip folder in your Downloads folder.
You can go to Sketch > Include Library > Add. ZIP library and select the library you’ve just downloaded.

MQTT Broker Connection

Node-RED and the MQTT broker need to be connected. Drag the following nodes to the flow.

To connect the MQTT broker to Node-Red, double-click the node. A new window pops up – as shown in the figure below.

mqtt out to publish the message to arduino UNO

Set topic UnoInTopic in the topic field and set QoS to 0
Click the Add new MQTT-broker option
Type test.mosquitto.org in the server field and set mqtt port 1883 in the port field

mqtt in to see the output of UnoInTopic

Set topic UnoInTopic in the topic field and set QoS to 0
Click the Add new MQTT-broker option same as mqtt out
Type test.mosquitto.org in the server field and set mqtt port 1883 in the port field

mqtt in to see the message are received from arduino UNO

Set topic UnoOutTopic in the topic field and set QoS to 0
Click the Add new MQTT-broker option same as mqtt out
Type test.mosquitto.org in the server field and set mqtt port 1883 in the port field

Arduino Code for MQTT Client

// Basic MQTT example
#include <PubSubClient.h>
#include <EthernetENC.h>

// Update these with values suitable for your network.
uint8_t mac[6] = {0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED};
IPAddress ip(192, 168, 10, 143);
//IPAddress server(192, 168, 9, 137);

EthernetClient ethClient;
PubSubClient mqttClient(ethClient);

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();
}

void reconnect() {
  // Loop until we're reconnected
  while (!mqttClient.connected()) {
    Serial.print("Attempting MQTT connection...");
    delay(1000);
    // Attempt to connect
    if (mqttClient.connect("MQTTClient01")) {
      Serial.println("connected");
      // Once connected, publish an announcement...
      mqttClient.publish("UnoOutTopic","hello world from UNO!");
      // ... and resubscribe
      mqttClient.subscribe("UnoInTopic");
    } else {
      Serial.print("failed, rc=");
      Serial.print(mqttClient.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

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

  Ethernet.begin(mac, ip);
//  Ethernet.begin(mac);

  // Allow the hardware to sort itself out
  delay(1000); 
  
  Serial.print("localIP: ");
  Serial.println(Ethernet.localIP());
  Serial.print("subnetMask: ");
  Serial.println(Ethernet.subnetMask());
  Serial.print("gatewayIP: ");
  Serial.println(Ethernet.gatewayIP());
  Serial.print("dnsServerIP: ");
  Serial.println(Ethernet.dnsServerIP());

  // connect to mqtt broker
  mqttClient.setServer("test.mosquitto.org", 1883);
//  mqttClient.setServer(server, 1883);
  mqttClient.setCallback(callback);

  delay(5000);
  
}

void loop()
{
  if (!mqttClient.connected()) {
    reconnect();
  }
  mqttClient.loop();
}

Testing an MQTT Client with Serial Monitor

Now, you can upload the code, open the serial monitor at a baud rate of 115200 and press the Arduino UNO RESET button.

Testing an MQTT Client with Node-RED

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

Github Link: download the project files

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