Controlling Relays and LEDs Through Retrieve Commands

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 publish data using MQTTX which contains commands to control the LEDs and relays. Then the Lynx-32 Development Board subscribes data to the Antares IoT Platform which contains two command options, namely if the Relay input is 1 then the relay will turn on; Relay input is 0 then the relay will turn off; LED is 1 then the LED will turn on; LED input is 0 then the LED will turn off.

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.

General Prerequisites ESP32 Wi-Fi

The additional materials specific to this project are as follows.

1. Shield Workshop Antares

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

If you have not installed Antares ESP MQTT version 1.0, you can follow these steps.

Antares Wi-Fi MQTT

1. MQTTX Software

If you have not installed the MQTTX Software, you can follow the steps in the following link.

MQTTX Installation

Follow These Steps

1. Launch the Arduino IDE application

2. Opening Sample Programme

You can open the programme code in the Arduino IDE via File > Examples > Antares ESP HTTP > Lynx32-Simple-Project > RETRIEVE_DATA_RELAY_LED.

Here is the sample programme code of RETRIEVE_DATA_RELAY_LED.

// Include necessary libraries
#include <AntaresESPMQTT.h> // Include the ESP32 HTTP library
#include <Adafruit_SSD1306.h> // Include the OLED library

// Replace these with your own credentials
#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 deviceName "YOUR-DEVICE-NAME"     // Replace with the Antares device name that was created

#define relayPin 25
#define ledPin 12

const unsigned long interval = 10000;    // 10 s interval to send message
unsigned long previousMillis = 0;  // will store last time message sent

AntaresESPMQTT antares(ACCESSKEY);

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());

  String relayValue = antares.getString("Relay"); // Change data field to "Relay"
  String ledValue = antares.getString("LED");     // Add reading for "LED" data field
  // Control relay based on received data
  if (relayValue == "1") {
  digitalWrite(relayPin, HIGH);
  } 
  else if (relayValue == "0") {
  digitalWrite(relayPin, LOW);
  }

  // Control LED based on received data
  if (ledValue == "1") {
  digitalWrite(ledPin, HIGH);
  } 
  else if (ledValue == "0") {
  digitalWrite(ledPin, LOW);
  }

  Serial.println("Received data - Relay: " + relayValue + " | LED: " + ledValue);
  
}

void setup() {
    Serial.begin(115200); // Initialize serial communication
    antares.setDebug(true); // Enable debugging for Antares
    antares.wifiConnection(WIFISSID, PASSWORD); // Connect to WiFi
    antares.setMqttServer();
    antares.setCallback(callback);
    pinMode(relayPin, OUTPUT); // Set relayPin as an output
    pinMode(ledPin, OUTPUT); // Set ledPin as an output
}

void loop() {
 /*
    Check if we're still connected to the MQTT broker/server.
    If disconnected, the device will try to reconnect.
   */
  antares.checkMqttConnection();
}

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.

#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 deviceName "YOUR-DEVICE-NAME"     // Replace with the Antares device name that was created

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 belowt

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	{ "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 } }

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 the Antares Server

After the MQTTX software setup is complete, it's time to send the PUBLISH command. The "Relay" field is filled with the string "1" or "0" as the command message for the Relay which will be sent via the MQTT protocol to the Antares server. The "LED" field is filled with the string "1" for LED ON or "0" for LED OFF as a command message for the LED that will be sent via the MQTT protocol to the Antares server.

{
      "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": "{\"Relay\":\"1\",\"LED\":\"1\"}"
          }
        },
        "ty": 4
      }
    }

If you have finished filling in the "test" field, then press the PUBLISH button on the MQTTX software located to the right of the Topic filling column, as shown below.

MQTTX Payload content image

If it has been published, the MQTTX page will have a message like the following.

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.

The data received by LYNX-32 with the MQTT protocol is in the form of Relay and LED 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:

OLED Display