ESP32 + MQTT + Home Assistant Integration (Secure by Design)¶

#pragma once

// WiFi — load from NVS in production; hardcoded here for brevity
#define WIFI_SSID    "your_ssid"
#define WIFI_PASS    "your_password"

// MQTT broker
#define MQTT_HOST    "192.168.1.10"   // broker LAN IP
#define MQTT_PORT    8883
#define MQTT_USER    "esp32_office"
#define MQTT_PASS    "your_device_password"  // store in NVS, not here
#define MQTT_CLIENT_ID "esp32_office_01"     // unique per device

// Topic namespace
#define TOPIC_TEMP   "home/office/env/temperature"
#define TOPIC_HUM    "home/office/env/humidity"
#define TOPIC_LED_CMD "home/office/led/cmd"
#define TOPIC_LED_STATE "home/office/led/state"
#define TOPIC_AVAIL  "home/office/env/availability"

// Pins
#define LED_PIN      2
#define I2C_SDA      21
#define I2C_SCL      22
#define PUBLISH_INTERVAL_MS 30000UL

// certs.h
#pragma once
static const char MQTT_CA_CERT[] = R"EOF(
-----BEGIN CERTIFICATE-----
MIICpDCCAYwCCQD... (your ca.crt contents) ...
-----END CERTIFICATE-----
)EOF";

#include <Arduino.h>
#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <Adafruit_BME280.h>
#include "config.h"
#include "certs.h"

static WiFiClientSecure tlsClient;
static PubSubClient     mqtt(tlsClient);
static Adafruit_BME280  bme;
static uint32_t         lastPublishMs = 0;
static bool             ledState = false;

// ── WiFi ─────────────────────────────────────────────────────────────────────

void connectWiFi() {
    if (WiFi.status() == WL_CONNECTED) return;
    Serial.printf("[WiFi] Connecting to %s ", WIFI_SSID);
    WiFi.begin(WIFI_SSID, WIFI_PASS);
    uint8_t attempts = 0;
    while (WiFi.status() != WL_CONNECTED && attempts < 30) {
        delay(500); Serial.print(".");
        attempts++;
    }
    if (WiFi.status() == WL_CONNECTED) {
        Serial.printf("\n[WiFi] Connected, IP: %s\n", WiFi.localIP().toString().c_str());
    } else {
        Serial.println("\n[WiFi] Failed — will retry");
    }
}

// ── MQTT callbacks ────────────────────────────────────────────────────────────

void onMqttMessage(char* topic, byte* payload, unsigned int length) {
    String msg;
    for (unsigned int i = 0; i < length; i++) msg += (char)payload[i];
    Serial.printf("[MQTT] Received %s = %s\n", topic, msg.c_str());

    if (String(topic) == TOPIC_LED_CMD) {
        ledState = (msg == "ON");
        digitalWrite(LED_PIN, ledState ? HIGH : LOW);
        // Publish confirmed state back
        mqtt.publish(TOPIC_LED_STATE, ledState ? "ON" : "OFF", false);
    }
}

// ── MQTT connect ──────────────────────────────────────────────────────────────

bool connectMqtt() {
    if (mqtt.connected()) return true;
    Serial.print("[MQTT] Connecting...");

    // LWT: broker publishes "offline" if ESP32 disconnects uncleanly
    bool ok = mqtt.connect(MQTT_CLIENT_ID, MQTT_USER, MQTT_PASS,
                           TOPIC_AVAIL, 1, true, "offline");
    if (ok) {
        Serial.println(" connected");
        mqtt.publish(TOPIC_AVAIL, "online", true);   // retained availability
        mqtt.subscribe(TOPIC_LED_CMD, 1);
        publishHADiscovery();
    } else {
        Serial.printf(" failed, rc=%d\n", mqtt.state());
    }
    return ok;
}

// ── HA MQTT Discovery ─────────────────────────────────────────────────────────

void publishHADiscovery() {
    // Temperature sensor
    const char* tempCfg = R"({
      "name":"Office Temperature",
      "unique_id":"esp32_office_temp",
      "state_topic":"home/office/env/temperature",
      "unit_of_measurement":"°C",
      "device_class":"temperature",
      "availability_topic":"home/office/env/availability",
      "device":{"identifiers":["esp32_office"],"name":"ESP32 Office","model":"DevKit","manufacturer":"Espressif"}
    })";
    mqtt.publish("homeassistant/sensor/esp32_office/temperature/config", tempCfg, true);

    // Humidity sensor
    const char* humCfg = R"({
      "name":"Office Humidity",
      "unique_id":"esp32_office_hum",
      "state_topic":"home/office/env/humidity",
      "unit_of_measurement":"%",
      "device_class":"humidity",
      "availability_topic":"home/office/env/availability",
      "device":{"identifiers":["esp32_office"]}
    })";
    mqtt.publish("homeassistant/sensor/esp32_office/humidity/config", humCfg, true);

    // LED light
    const char* ledCfg = R"({
      "name":"Office LED",
      "unique_id":"esp32_office_led",
      "command_topic":"home/office/led/cmd",
      "state_topic":"home/office/led/state",
      "availability_topic":"home/office/env/availability",
      "payload_on":"ON","payload_off":"OFF",
      "device":{"identifiers":["esp32_office"]}
    })";
    mqtt.publish("homeassistant/light/esp32_office/led/config", ledCfg, true);
}

// ── Sensor publish ────────────────────────────────────────────────────────────

void publishSensors() {
    char buf[16];
    snprintf(buf, sizeof(buf), "%.1f", bme.readTemperature());
    mqtt.publish(TOPIC_TEMP, buf, false);
    snprintf(buf, sizeof(buf), "%.1f", bme.readHumidity());
    mqtt.publish(TOPIC_HUM, buf, false);
    Serial.printf("[MQTT] Published temp=%s hum=%s\n", buf, buf);
}

// ── Setup / Loop ─────────────────────────────────────────────────────────────

void setup() {
    Serial.begin(115200);
    pinMode(LED_PIN, OUTPUT);
    Wire.begin(I2C_SDA, I2C_SCL, 400000);

    if (!bme.begin(0x76)) {
        Serial.println("[BME280] Not found — check wiring");
    }

    tlsClient.setCACert(MQTT_CA_CERT);  // pin our self-signed CA
    // tlsClient.setInsecure();  // ← NEVER use this in production

    mqtt.setServer(MQTT_HOST, MQTT_PORT);
    mqtt.setCallback(onMqttMessage);
    mqtt.setBufferSize(512);  // increase if discovery JSON is larger
    mqtt.setKeepAlive(30);

    connectWiFi();
    connectMqtt();
}

void loop() {
    // Reconnect if needed — non-blocking (no delay)
    if (WiFi.status() != WL_CONNECTED) connectWiFi();
    if (!mqtt.connected()) connectMqtt();

    mqtt.loop();  // process incoming messages + keepalive

    // Publish sensor data on interval
    if (millis() - lastPublishMs > PUBLISH_INTERVAL_MS) {
        publishSensors();
        lastPublishMs = millis();
    }
}