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.
You can open the programme code in the Arduino IDE via File > Examples > Antares ESP HTTP > Lynx32-Simple-Project > SEND_DATA_RETRIEVE_DATA_OLED.
Here is the sample programme code of SEND_DATA_RETRIEVE_DATA_OLED.
3. Set WiFi Credential and Antares Credential in Program Code
Change the HTTP Protocol parameters in the following variables *ACCESSKEY, *WIFISSID, *PASSWORD, *projectName, and *deviceName. Adjust to the parameters in the Antares console.
The *Access key parameter is obtained from your Antares account page.
Access Key Location on Antares Account Page
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.
WIFISSID
The *PASSWORD parameter is obtained from the Wi-Fi password you are currently using.
The parameters *projectName and *deviceName are obtained from the Application Name and Device Name that have been created in the Antares account.
Application Name Display
Device Name Display
4. Compile and Upload Program
Connect the Lynx-32 with your computer and make sure the Communication Port is read.
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).
Device Manager Display
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.
Display of Board Specifications and Ports Used
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
Compile Icon for Tick and Upload Icon for Arrow
The Tick icon on the Arduino IDE is just the verify process. Usually used to Compile 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.
If the programme upload is successful, it will look like the following image.
Arduino IDE page image after successful upload
After uploading the programme, you can view the serial monitor to debug the programme. The serial monitor icon is shown in the following image.
Serial Monitor Icon
Set the serial baud rate to 115200 and select BothNL & CR. The result will look like the following image.
Serial Monitor Display
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.
5. MQTTX Software Setup
Open the MQTTX App, then select New Connection
Creating a New Connection
In order to configure MQTTX with Antares broker, adjust the Name, Host and Port as shown below, then click Connect.
Antares MQTT Broker Configuration
If it is connected, there is a notification as shown below
Antares Broker MQTTX Connected
Enter Topic and Payload in the fields in MQTTX.
Topic and Payload pages in MQTTX
Field
Value
Topic
/oneM2M/req/your-access-key/antares-cse/json
Payload
Customise your-access-key, your-application-name, and your-device-name to the names registered to your Antares account. Fill in the "Field" data and "Value" data in "con" as you wish.
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.
Publish to send the message to the Antares server
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.
If you have finished filling in the "Test" field, then press the Publish button on the MQTTX software, as shown below.
Image of MQTTX Payload content
Publish to send the message to the Antares server
Message Notification Published
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.
Image of the Antares Console Page when data is successfully received from MQTTX.
Image of the Antares Console Page when data is successfully received from the DHT11 Sensor.
The data received by LYNX-32 with the MQTT protocol is in the form of Test Data variables.
8. View Retrieve Message
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:
// 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);
}
}
#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
