# 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. {% content-ref url="../../general-prerequisites-esp32-wi-fi" %} [general-prerequisites-esp32-wi-fi](https://docs.antares.id/en/code-and-library-examples/esp32-wi-fi/general-prerequisites-esp32-wi-fi) {% endcontent-ref %} 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. {% hint style="info" %} If you have not installed **Antares ESP MQTT version 1.0**, you can follow these steps. [antares-wi-fi-mqtt](https://docs.antares.id/en/getting-started/arduino-library-installation/antares-wi-fi-mqtt "mention") {% endhint %} 3. MQTTX Software {% hint style="info" %} If you have not installed the MQTTX Software, you can follow the steps in the following link. [mqttx-installation](https://docs.antares.id/en/getting-started/software-installation/mqttx-installation "mention") {% endhint %} ## Follow These Steps ### 1. Launch the Arduino IDE application ### 2. Opening Sample Programme {% hint style="info" %} You can open the programme code in the Arduino IDE via **File > Examples > Antares ESP HTTP > Lynx32-Simple-Project > RETRIEVE\_DATA\_RELAY\_LED.** {% endhint %} Here is the sample programme code of **RETRIEVE\_DATA\_RELAY\_LED**. ```arduino // Include necessary libraries #include // Include the ESP32 HTTP library #include // 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. ```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" // Replace with the Antares application name that was created #define deviceName "YOUR-DEVICE-NAME" // Replace with the Antares device name that was created ``` {% hint style="info" %} The **\*Access key** parameter is obtained from your Antares account page. {% endhint %}

Access Key Location on Antares Account Page

{% 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 %}

WIFISSID

{% 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 %}

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. {% 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 %}

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

{% 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.

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

{% 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**

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

FieldValue
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
      }
    }
{% hint style="info" %} 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. {% 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.

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. ```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": "{\"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.

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