tangible-interaction/Mqtt-Communication/01_MQTT_Client_Button/01_MQTT_Client_Button.ino

/*
  Project: 01_MQTT_Client_Button
  Author: Luis Quintero
  Date: 2025-10-03
  Board: ESP32-S2 (Adapt Pin Layout for ESP32 or ESP32-S3)
  Description:
    Basic sketch demonstrating a button inputs with MQTT. 
    
    Behavior:
    - The built-in button sends a message to MQTT broker.
    
    All communication goes through MQTT Messages. Note that
    the WiFi and MQTT values default to the credentials
    required to connect with the MQTT Broker at Extrality Lab.
*/

#include <WiFi.h>
#include <PubSubClient.h>

// WiFi setup - Default setup to connect to Extrality Lab WiFi
const char *wifi_ssid = "dsv-extrality-lab";            // Enter your Wi-Fi name
const char *wifi_password = "expiring-unstuck-slider";  // Enter Wi-Fi password

WiFiClient espClient; // variable in charge of WiFi connection

// MQTT Broker setup - Default setup to connect to ExtralityLab Broker
const char *mqtt_broker = "inf-liva-server-eth.dsv.local.su.se";
const int mqtt_port = 1883;
const char *mqtt_username = "esp32";
const char *mqtt_password = "extrality";

PubSubClient client(espClient); // variable in charge of Mqtt connection
String client_id = "";

////////////////////////////////////
//////////// PIN DEFINITION
////////////////////////////////////

// PIN INPUTS
const int PIN_BTN = 0;    //Built in button
bool boardBtnState;     // variable to store current button state
bool lastBoardBtnState = HIGH;  // using INPUT_PULLUP: HIGH = not pressed (pullup), LOW = pressed

// PIN OUTPUT LED CONTROL
const int PIN_LED_DIG = 13;  // Onboard LED Digital (GPIO 13 in SparkFun ESP32S2 board)
bool ledDigitalState = LOW;


////////////////////////////////////
//////////// MQTT SETUP
////////////////////////////////////

//// Topics (Inputs sent to MQTT Broker)
// Digital
char topicBoardButton[50] = "/D0_BoardBtn";

//// Subscribers (Actuators received from MQTT Broker)
//Digital
// char subsD13_out_BoardLED[50] = "/D13_boardLED";

////////////////////////////////////
//////////// CUSTOM FUNCTIONS
////////////////////////////////////


String getMacAddress() {
  // Get the MAC address of the ESP32
  String macStr = String(WiFi.macAddress());  // Format: "AA:BB:CC:DD:EE:FF"
  Serial.print("Full MAC address:");
  Serial.println(macStr);

  // Optional: Remove colons if you want a clean topic name
  macStr.replace(":", "");
  String macStr4 = macStr.substring(macStr.length() - 4);
  macStr4.toLowerCase();

  Serial.print("Device ID (Last four characters): ");
  Serial.println(macStr4);
  return macStr4;
}


bool ensureMqtt() {
  if (client.connected()) return true;
  while (!client.connected()) {
    Serial.printf("The client %s connects to the ExtralityLab MQTT broker\n", client_id.c_str());
    bool isConnected = client.connect(client_id.c_str(), mqtt_username, mqtt_password);
    if (isConnected) {
      Serial.println("ExtralityLab MQTT broker connected");
      return true;
    } else {
      Serial.print("Failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }
}


// Notify that there is a function called `mqttCallback`. Implementation is further below.
void mqttCallback(char *subscriber, byte *payload, unsigned int length);

////////////////////////////////////
//////////// SETUP
////////////////////////////////////

void setup() {

  // Set software serial baud to 115200;
  Serial.begin(115200);
  while (!Serial && millis() < 5000);
  delay(100);

  //// Set up pinModes
  // Inputs
  pinMode(PIN_BTN, INPUT_PULLUP); // Built-in button

  // Outputs/Actuators
  pinMode(PIN_LED_DIG, OUTPUT); // Built-in LED as Digital
  digitalWrite(PIN_LED_DIG, LOW);

  ///////////////////
  // Connecting to a WiFi network
  WiFi.begin(wifi_ssid, wifi_password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
  }
  Serial.println("Connected to the Wi-Fi network");


  ///////////////////
  // Connecting to MQTT broker
  client.setServer(mqtt_broker, mqtt_port);
  client.setCallback(mqttCallback); // What would happen with each MQTT message

  // Get MAC Address to create client ID
  String deviceMacID = getMacAddress();
  client_id = "esp32-client-";
  client_id += deviceMacID; // unique clientID based on MAC address

  bool connectedMqtt = ensureMqtt();

  ///////////////////
  // Publish Topics (one per input)
  Serial.println("\t[[MQTT Published Topics]]");

  // Build the topics strings, preceding the client_id
  String topic;

  topic = deviceMacID + topicBoardButton;
  topic.toCharArray(topicBoardButton, sizeof(topicBoardButton));
  Serial.println(topicBoardButton);
}

////////////////////////////////////
//////////// MAIN LOOP
////////////////////////////////////

void loop() {

  // Ensure connections
  ensureMqtt();
  client.loop();

  // ---- topicBoardButton: Publish on change ---
  boardBtnState = digitalRead(PIN_BTN);
  if (boardBtnState != lastBoardBtnState) {
    lastBoardBtnState = boardBtnState;

    client.publish(topicBoardButton, String(boardBtnState).c_str());
    Serial.print("Board button: ");
    Serial.println(boardBtnState);

    delay(200); // small idle to debounce
  }

}

////////////////////////////////////
//////////// MQTT SUBSCRIPTION CALLBACKS
////////////////////////////////////

void mqttCallback(char *subscriber, byte *payload, unsigned int length)
{
  Serial.print("Message arrived in Subscriber: ");
  Serial.println(subscriber);
  Serial.print("Message:");

  String message;
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
    message += (char)payload[i];
  }
  Serial.println("-----------------------");
}