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Arduino Data on Mqtt – DZone IoT


MQTT is an OASIS standard messaging protocol for the Internet of Things (IoT) and one of the protocols supported by akenza. 

It is designed as an extremely lightweight publish/subscribe messaging protocol that is ideal for connecting remote devices with a small code footprint and minimal network bandwidth. MQTT is used in various industries. 

To run this project, we used akenza as an IoT platform, as it runs an open-source MQTT broker from Eclipse MosquittoBy using a combination of MQTT and API functionalities, we have been able to automatically create Digital Twins for our device.

As Hardware, we have chosen an Arduino Uno WiFi Rev2.

Arduino Uno WiFi Rev2.

1. Configure the Arduino Device

1.1 Set up the WiFi Connection

To have the Arduino Uno Wifi able to connect to WiFi, we used the WiFiNINA library, available in the Library Manager of Arduino IDE.

1.1.1 Manage Username and Password

To manage Username and Password, we have created an additional header file called arudino_secrets.h 

#define SECRET_SSID "<your username>"
#define SECRET_PASS "<your password>"

1.1.2 WiFi Connection Code

The code to connect Arduino to WiFi is reported as below:

#include <WiFiNINA.h>
#include "arduino_secrets.h"

///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID;     // your network SSID (name)
char pass[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)

WiFiClient wifiClient;

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // attempt to connect to Wifi network:
  Serial.print("Attempting to connect to WPA SSID: ");
  Serial.println(ssid);
  while (WiFi.begin(ssid, pass) != WL_CONNECTED) {
    // failed, retry
    Serial.print(".");
    delay(5000);
  }

  Serial.println("You're connected to the network");
  Serial.println();
}

void loop()
{}

1.2 Set up the MQTT Connection to akenza

For security reasons, akenza only supports authenticated connections via MQTT. For this, we have chosen as library PubSubClient to manage our MQTT connection. This enables us to use username and passwords in our connection string. 

#include <PubSubClient.h>

//MQTTClient mqttClient(WiFiClient);

char host[] = "mqtt.akenza.io";
char clientid[] = "Arduino";
char username[] = "<copy from Akenza Device Api configuration>";
char password[] = "<copy from Akenza Device Api configuration>";
char outTopic[] = "<copy from Akenza Device Api configuration>";

PubSubClient client(host, 1883, callback, wifiClient);

void setup() {
  if (client.connect(host, username, password)) {
    Serial.print("Connected to ");
    Serial.println(host);
    Serial.println();
    
    boolean r = client.subscribe(outTopic);
    Serial.print("Subscribed to ");
    Serial.println(outTopic);
    Serial.println();
    } 
    else {
      // connection failed
      // mqttClient.state() will provide more information
      // on why it failed.
      Serial.print("Connection failed: ");
      Serial.println(client.state());
      Serial.println();
  }
}

Akenza accepts messages in JSON format for MQTT connections. To build up a well-formed JSON object, we make use of the ArduinoJson library.

#include <ArduinoJson.h>

void loop()
{
  StaticJsonDocument<256> doc;
  doc["Temperature"] = 22;
  doc["Humidity"] = 68;
  doc["Light"] = 96;

  // Add an array
  JsonArray data = doc.createNestedArray("data");
  data.add(48);
  data.add(2.3);
  
  char out[128];
  int b =serializeJson(doc, out);
  Serial.print("publishing bytes = ");
  Serial.println(b,DEC);
  
  boolean rc = client.publish(outTopic, out);
  
  // The above line prints:
  // {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}
  delay(5000);
  client.loop();
}

Please note that these are just examples of data; if you would like to send to the cloud data coming from a sensor, the code has to be adapted accordingly.

2. Connect the Arduino device via MQTT on akenza

To safely communicate with akenza, a secret must be generated that has to be provided in the topic structure of the uplink request.

This step has to be performed for all devices with the same connection parameters which you want to connect. Each device will be uniquely identified by a specific ID accordingly. A secret will be generated after the creation of the MQTT device connector on the Data Flow.

2.1.1 Setting up an MQTT Device Connector on akenza

Go to Data Flow in the menu and select Create Data Flow

Choose MQTT as a device connector. As Device Type, select Passthrough to receive data in the same format as sent from your MQTT device.

Choose one or multiple Output Connectors of your choice. There are several options to choose from. In this tutorial, we choose the Akenza DB

 Output Connectors

2.2 Create an MQTT Device 

To create a new MQTT device, select Create Device within the menu of the Asset Inventory. Add a device name and optionally a description, Asset Tags, and Custom Fields. Select Next and choose your created MQTT- Data Flow. Select Proceed.

Create new device.

Generate a random ID for this device by clicking Generate ID. Finish the process by clicking on the button Create Device. Your device will be now displayed on the Asset Inventory Overview.

2.3 Set up the Arduino Device

As a next step, the Arduino device has to be now configured to send data to the MQTT Broker of akenza. Go to Asset Inventory and use the filter to search for your device. Open the device detail page by selecting your device. Within API-Configuration, all the required information is available to set up the device as an MQTT- client.

Go to Asset Inventory and use the filter to search for your device. Open the device detail page by selecting your device.

Now you have all the elements needed to set up your code on Arduino and stream data via MQTT to akenza.

The final code is reported as below:

#include <SPI.h>
#include <PubSubClient.h>
#include <WiFiNINA.h>
#include <ArduinoJson.h>

#include "arduino_secrets.h"

///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID;     // your network SSID (name)
char pass[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)

char host[] = "mqtt.akenza.io";
char clientid[] = "Arduino";
char username[] = "0783ddd64683f579";
char password[] = "bd604gmgit0x7kilc8puok3g2rxsldl2";
char outTopic[] = "/up/bd604gmgit0x7kilc8puok3g2rxsldl2/id/99E77F4ECC728656";

//set interval for sending messages (milliseconds)
const long interval = 8000;
unsigned long previousMillis = 0;

int count = 0;

//receive data
void callback(char* topic, byte* payload, unsigned int length) {

  char str[length+1];
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  int i=0;
  
  for (i=0;i<length;i++) {
    Serial.print((char)payload[i]);
    str[i]=(char)payload[i];
  }

  str[i] = 0; // Null termination
  Serial.println();
  
  StaticJsonDocument <256> doc;
  deserializeJson(doc,payload);

  // deserializeJson(doc,str); can use string instead of payload
  const char* sensor = doc["sensor"];
  long time          = doc["time"];
  float latitude    = doc["data"][0];
  float longitude   = doc["data"][1];

  Serial.println("latitude =");
  Serial.println(latitude,2);
  Serial.println(sensor);
  
}

WiFiClient wifiClient;
PubSubClient client(host, 1883, callback, wifiClient);

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // attempt to connect to Wifi network:
  Serial.print("Attempting to connect to WPA SSID: ");
  Serial.println(ssid);
  while (WiFi.begin(ssid, pass) != WL_CONNECTED) {
    // failed, retry
    Serial.print(".");
    delay(5000);
  }

  Serial.println("You're connected to the network");
  Serial.println();

  if (client.connect(host, username, password)) {
    Serial.print("Connected to ");
    Serial.println(host);
    Serial.println();
    
    boolean r = client.subscribe(outTopic);
    Serial.print("Subscribed to ");
    Serial.println(outTopic);
    Serial.println();
    } 
    else {
      // connection failed
      Serial.println("Connection failed ");
      Serial.println(client.state());
      Serial.println();
  }
}

void loop()
{
  StaticJsonDocument<256> doc;
  doc["Temperature"] = 22;
  doc["Humidity"] = 68;
  doc["Light"] = 96;

  // Add an array
  JsonArray data = doc.createNestedArray("data");
  data.add(48);
  data.add(2.3);
  
  char out[128];
  int b =serializeJson(doc, out);
  Serial.print("publishing bytes = ");
  Serial.println(b,DEC);
  
  boolean rc = client.publish(outTopic, out);
  
  // The above line prints:
  // {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}
  delay(5000);
  client.loop();
}

It automatically decodes the received JSON and visualizes data received from the Arduino device. Incoming data can be viewed on the Device Detail Page within Message Logs.

Incoming data can be viewed on the Device Detail Page within Message Logs.

Incoming data are visualized on Data Overview as Device Data KPIs and also on the History chart.

Incoming data are visualized on Data Overview as Device Data KPIs and also on the History chart.





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