# DHT 11 Send Data and Retrieve Data displayed on OLED

In this project, you will use the **Antares Workshop Shield** on the **Lynx-32 Development Board** module. In this **Antares Shield Workshop**, there are temperature, humidity (DHT11), relay, LED, and push button sensors. You will monitor the temperature and humidity with a specified interval period. The data sent by the sensors can be monitored through the Antares console and displayed on the **OLED**. You can also send messages in the form of string data displayed on the OLED display. This data transmission process uses **MQTTX Software** to send data to the **Antares IoT Platform.**

## Prerequisites

The materials required follow the **General Prerequisites** on the previous page. If you have not prepared the requirements on that page, then you can visit the following page.

{% content-ref url="/pages/Zpk3iTltrVZubNhHlGNm" %}
[General Prerequisites ESP32 Wi-Fi](/en/code-and-library-examples/esp32-wi-fi/general-prerequisites-esp32-wi-fi.md)
{% endcontent-ref %}

The additional materials specific to this project are as follows.

1. Shield Workshop Antares
2. I2C-based 0.96inch 128x64 pixel SSD1036 OLED module

<figure><img src="/files/fEaGYo4Mk5nBeWEOa6rm" alt="" width="345"><figcaption><p>SSD1036 0.96inch OLED Module Picture</p></figcaption></figure>

3. Antares ESP HTTP Library. This documentation uses the **Antares ESP MQTT library version 1.0.**

{% hint style="info" %}
If you have not installed **Antares ESP MQTT version 1.0**, you can follow these steps.

[Antares Wi-Fi MQTT](/en/getting-started/arduino-library-installation/antares-wi-fi-mqtt.md)
{% endhint %}

4. DHT11 Library. This documentation uses **DHT11 Sensor Library version 1.4.4.**

{% hint style="info" %}
If you have not installed the **DHT11 Sensor Library version 1.4.4**. you can follow the steps in the following link.

[DHT11 Sensor Library](/en/getting-started/arduino-library-installation/dht11-sensor-library.md)
{% endhint %}

5. SSD1306 OLED Library. This documentation uses **Adafruit SSD1306 by Adafruit version 2.5.7.**

{% hint style="info" %}
If you have not installed the **Adafruit SSD1306 by Adafruit library version 2.5.7.** you can follow the steps in the following link.

[Adafruit SSD1306](/en/getting-started/arduino-library-installation/adafruit-ssd1306.md)
{% endhint %}

6. MQTTX Software&#x20;

{% hint style="info" %}
If you have not installed the **MQTTX Software**, you can follow the steps in the following link.

[MQTTX Installation](/en/getting-started/software-installation/mqttx-installation.md)
{% endhint %}

## Follow These Steps

### 1. Launch the Arduino IDE application

### 2. Opening Sample Programme&#x20;

{% hint style="info" %}
You can open the programme code in the Arduino IDE via **File > Examples > Antares ESP HTTP > Lynx32-Simple-Project > SEND\_DATA\_RETRIEVE\_DATA\_OLED.**
{% endhint %}

Here is the sample programme code of **SEND\_DATA\_RETRIEVE\_DATA\_OLED**.

```arduino
// Include necessary libraries
#include <AntaresESPMQTT.h>   // Include AntaresESP32HTTP library for Antares platform communication
#include <Adafruit_SSD1306.h>   // Include Adafruit_SSD1306 library for OLED display
#include "DHT.h"               // Include DHT library for temperature and humidity sensor

#define DHTPIN 14               // Define the pin connected to the DHT sensor
#define DHTTYPE DHT11           // Set the DHT sensor type as DHT11

#define ACCESSKEY "YOUR-ACCESS-KEY"       // Replace with your Antares account access key
#define WIFISSID "YOUR-WIFI-SSID"         // Replace with your Wi-Fi SSID
#define PASSWORD "YOUR-WIFI-PASSWORD"     // Replace with your Wi-Fi password

#define projectName "YOUR-APPLICATION-NAME"   // Replace with the Antares application name that was created
#define deviceNameSensor "YOUR-DEVICE-NAME-1"     // Replace with the Antares device name that was created
#define deviceNameMQTT "YOUR-DEVICE-NAME-2" // Replace with your Antares device name, make sure all devices are in one application

AntaresESPMQTT antares(ACCESSKEY); // Create AntaresESP32HTTP object
DHT dht(DHTPIN, DHTTYPE);            // Create DHT object for sensor readings

#define SCREEN_WIDTH 128          // Set OLED screen width
#define SCREEN_HEIGHT 64          // Set OLED screen height
#define OLED_RESET -1             // Define OLED reset pin, not used in this case

const unsigned long interval = 5000; // Interval for sending sensor data (5 seconds)
const unsigned long interval2 = 10000; // Interval for receiving Postman data (10 seconds)
unsigned long previousMillis = 0;     // Store the last time sensor data was sent
unsigned long previousMillis2 = 0;    // Store the last time Postman data was received

String testData;             // Store received Postman data
String lastData = "";        // Store last received Postman data

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET); // Create OLED display object

bool showSensorData = true;  // Flag to control displaying sensor data

void callback(char topic[], byte payload[], unsigned int length) {
  antares.get(topic, payload, length);

  Serial.println("New Message!");
  Serial.println("Topic: " + antares.getTopic());
  Serial.println("Payload: " + antares.getPayload());

  testData = antares.getString("Test");
  Serial.println("Received: " + testData);
  if (testData!="null")
  {
    if (lastData!=testData)
    {
      lastData=testData;
      display.clearDisplay();
      display.setTextSize(1);
      display.setTextColor(SSD1306_WHITE);
      display.setCursor(0, 0);
      display.println("Received: " + testData);
      display.display();
    }
  }
}

void setup() {
  Serial.begin(115200);                 // Initialize serial communication
  antares.setDebug(true);               // Enable debugging for Antares
  antares.wifiConnection(WIFISSID, PASSWORD);
  antares.setMqttServer();
  antares.setCallback(callback);

  dht.begin();                          // Initialize DHT sensor

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Initialize OLED display
    Serial.println(F("SSD1306 allocation failed"));
    for (;;)
      ;
  }

  display.clearDisplay();               // Clear the display buffer
  display.display();                    // Display the cleared buffer
}

void loop() {
   /*
    Check if we're still connected to the MQTT broker/server.
    If disconnected, the device will try to reconnect.
   */
  antares.checkMqttConnection();
  // Send sensor data
  if (millis() - previousMillis > interval) {
    previousMillis = millis();

    float hum = dht.readHumidity();      // Read humidity from DHT sensor
    float temp = dht.readTemperature();  // Read temperature from DHT sensor

    if (isnan(hum) || isnan(temp)) {     // Check if sensor reading is valid
      Serial.println("Failed to read DHT sensor!");
      return;
    }

    // Add temperature and humidity data to the storage buffer
    antares.add("temperature", temp);
    antares.add("humidity", hum);

    // Send data from the storage buffer to Antares
    antares.publish(projectName, deviceNameSensor);

    // Display temperature and humidity on OLED
    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.println("Temp: " + String(temp) + " *C");
    display.println("Humidity: " + String(hum) + " %");
    display.display();
  }
  
  // Receive and display latest data
  if (millis() - previousMillis2 > interval2) {
    previousMillis2 = millis();
    antares.retrieveLastData(projectName,deviceNameMQTT);
   }
}

```

### 3. Set WiFi Credential and Antares Credential in Program Code&#x20;

Change the HTTP Protocol parameters in the following variables **\*ACCESSKEY, \*WIFISSID, \*PASSWORD, \*projectName**, and **\*deviceName**. Adjust to the parameters in the Antares console.

```arduino
#define ACCESSKEY "YOUR-ACCESS-KEY"       // Replace with your Antares account access key
#define WIFISSID "YOUR-WIFI-SSID"         // Replace with your Wi-Fi SSID
#define PASSWORD "YOUR-WIFI-PASSWORD"     // Replace with your Wi-Fi password

#define projectName "YOUR-APPLICATION-NAME"          // Antares project name
#define deviceNameSensor "YOUR-DEVICE-NAME-1"   // Name of the device sending sensor data
#define deviceNamePostman "YOUR-DEVICE-NAME-2"     // Name of the device receiving data
```

{% hint style="info" %}
The **\*Access key** parameter is obtained from your Antares account page.
{% endhint %}

<figure><img src="/files/vKIKahSM9WsoNdYrIo6o" alt=""><figcaption><p>Access Key Location on Antares Account Page</p></figcaption></figure>

{% hint style="info" %}
The **WIFISSID** parameter is obtained from the name of the **Wifi / Hotspot** that is currently being used by you. for example in the image below.
{% endhint %}

<figure><img src="/files/1YWYZS4Q2uYxH6phtARQ" alt=""><figcaption><p>WIFISSID</p></figcaption></figure>

{% hint style="info" %}
The **\*PASSWORD** parameter is obtained from the **Wi-Fi password** you are currently using.
{% endhint %}

{% hint style="info" %}
The parameters **\*projectName** and **\*deviceName** are obtained from the **Application Name** and **Device Name** that have been created in the Antares account.
{% endhint %}

<figure><img src="/files/bDel2t2JrMlg3RNweQQM" alt=""><figcaption><p>Application Name Display</p></figcaption></figure>

<figure><img src="/files/wvZtJO4BjTcc1jYSd2vK" alt=""><figcaption><p>Device Name Display</p></figcaption></figure>

### 4. Compile and Upload Program

Connect the **Lynx-32** with your computer and make sure the **Communication Port** is read.

{% hint style="info" %}
On Windows operating systems the check can be done via **Device Manager**. If your **Lynx-32** is read then the **USB-Serial CH340** appears with the port adjusting the port availability (in this case it reads **COM4**).
{% endhint %}

<figure><img src="/files/EYILW4jcOs6sMXRxmxjh" alt=""><figcaption><p>Device Manager Display</p></figcaption></figure>

Set up the **ESP32** board by clicking **Tools > Board > esp32** in the Arduino IDE, then make sure the **ESP32 Dev Module** is used. Select the port according to the communication port that is read (in this case COM4). The result will look like the following image.

<figure><img src="/files/V2G1PfRzcS6WbvsDx5S8" alt="" width="464"><figcaption><p>Display of Board Specifications and Ports Used</p></figcaption></figure>

After all the setup is complete, upload the programme by pressing the arrow icon as shown below. Wait for the compile and upload process to finish

<figure><img src="/files/SbWGiGKiBtavySv74cfA" alt=""><figcaption><p>Compile Icon for Tick and Upload Icon for Arrow</p></figcaption></figure>

{% hint style="info" %}
**The Tick icon** on the Arduino IDE is just the verify process. Usually used to C**ompile** the programme to find out whether there are errors or not. \
**The Arrow icon** on the Arduino IDE is the verify and upload process. Usually used to **Compile** the programme as well as Flash the programme to the target board.
{% endhint %}

If the programme upload is successful, it will look like the following image.

<figure><img src="/files/h6QGODJTrMnmqvuFAi6e" alt=""><figcaption><p>Arduino IDE page image after successful upload</p></figcaption></figure>

After uploading the programme, you can view the **serial monitor** to debug the programme. The **serial monitor** icon is shown in the following image.

<figure><img src="/files/8S7xm5y59s4BMsMVKXhO" alt=""><figcaption><p>Serial Monitor Icon</p></figcaption></figure>

Set the **serial baud rate** to 115200 and select BothNL & CR. The result will look like the following image.

<figure><img src="/files/zNXEf9gAIpGGaG6s1nNO" alt=""><figcaption><p>Serial Monitor Display</p></figcaption></figure>

{% hint style="danger" %}
Make sure the **serial baud rate** matches the value defined in the programme code. If the **serial baud rate** is not the same between **the programme code** and **the serial monitor**, the ASCII characters will not be read properly.
{% endhint %}

### 5. MQTTX Software Setup

**Open the MQTTX App, then select New Connection**

<figure><img src="/files/I8Px9gDjlPPmLaiFncxs" alt=""><figcaption><p>Creating a New Connection</p></figcaption></figure>

In order to configure MQTTX with Antares broker, adjust the Name, Host and Port as shown below, then click Connect.

<figure><img src="/files/BhRxLGdQ63X7IRxXqnRL" alt=""><figcaption><p>Antares MQTT Broker Configuration</p></figcaption></figure>

If it is connected, there is a notification as shown below

<figure><img src="/files/FzhpoD65ttPhDgBdSweB" alt=""><figcaption><p>Antares Broker MQTTX Connected</p></figcaption></figure>

Enter **Topic** and **Payload** in the fields in MQTTX.

<figure><img src="/files/7Uybrtrp00D3FlzZQkxn" alt=""><figcaption><p>Topic and Payload pages in MQTTX</p></figcaption></figure>

<table><thead><tr><th width="111">Field</th><th>Value</th></tr></thead><tbody><tr><td><strong>Topic</strong></td><td><mark style="color:red;"><code>/oneM2M/req/your-access-key/antares-cse/json</code></mark></td></tr><tr><td><strong>Payload</strong></td><td><pre class="language-json"><code class="lang-json">{
      "m2m:rqp": {
        "fr": "your-access-key",
        "to": "/antares-cse/antares-id/nama-aplikasi-anda/nama-device-anda",
        "op": 1,
        "rqi": 123456,
        "pc": {
          "m2m:cin": {
            "cnf": "message",
            "con": "{\"your-first-data\":\"the-integer-value\",\"your-second-data\":\"the-string-data\"}"
          }
        },
        "ty": 4
      }
    }
</code></pre></td></tr></tbody></table>

{% hint style="info" %}
Customise <mark style="color:red;">your-access-key</mark>, <mark style="color:red;">your-application-name</mark>, and <mark style="color:red;">your-device-name</mark> to the names registered to your Antares account. Fill in the "Field" data and "Value" data in "con" as you wish.
{% endhint %}

In the MQTTX software, enter the Topic and Payload that you want to use. Then click Publish to send the message from MQTTX to the Antares server.

<figure><img src="/files/lDekytsV5B5Su1tkVam4" alt=""><figcaption><p>Publish to send the message to the Antares server</p></figcaption></figure>

### **6.** Sending MQTTX Messages to Antares Server

After the MQTTX software setup is complete, it's time to send the PUBLISH command. The "Test" field is filled with the string "Hello Antares" as the message that will be sent via the MQTT protocol to the Antares server.

```json
{
      "m2m:rqp": {
        "fr": "your-access-key",
        "to": "/antares-cse/antares-id/nama-aplikasi-anda/nama-device-anda",
        "op": 1,
        "rqi": 123456,
        "pc": {
          "m2m:cin": {
            "cnf": "message",
            "con": "{\"Test\":\"Hallo Antares\"}"
          }
        },
        "ty": 4
      }
    }
```

If you have finished filling in the "Test" field, then press the **Publish** button on the MQTTX software, as shown below.

<figure><img src="/files/pD9Y4D2BrygIXLdTLd6D" alt=""><figcaption><p>Image of MQTTX Payload content</p></figcaption></figure>

Publish to send the message to the Antares server

<figure><img src="/files/azXc6lIl1OXgqvYyQwQe" alt=""><figcaption><p>Message Notification Published</p></figcaption></figure>

### 7. Check Data in Antares

After uploading the programme successfully, then open the device antares page and see if the data has been successfully sent.

<figure><img src="/files/8Yi3Uh3bI3epos4EDMZo" alt=""><figcaption><p>Image of the Antares Console Page when data is successfully received from MQTTX.</p></figcaption></figure>

<figure><img src="/files/e0UJ7270T8GzTvgDBBoo" alt=""><figcaption><p>Image of the Antares Console Page when data is successfully received from the DHT11 Sensor.</p></figcaption></figure>

{% hint style="info" %}
The data received by **LYNX-32** with the MQTT protocol is in the form of Test Data variables.
{% endhint %}

### 8. View Retrieve Message&#x20;

Retrieve data from the **Antares IoT Platform** and display it on the OLED display after connecting to Wi-Fi as shown in the figure below:

<figure><img src="/files/EP0mgzaLRIaMg8Y5kjFq" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/1NNf3vbXQ8HTzJLBAyRp" alt=""><figcaption><p>OLED Display</p></figcaption></figure>


---

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