🔄 MQTT Lifecycle (firmware side)

How an ESP32 talks to the Backend MQTT broker, from boot to operation.

Telemetry Pattern

JsonDocument doc;
JsonObject state = doc["state"].to<JsonObject>();
state["temperature"] = 23.5;
state["humidity"] = 60.0;

String message;
serializeJson(doc, message);
core.mqtt().publish(topic.c_str(), message.c_str(), false);

• Always wrap payload in {"state": { ... }}
• Check core.mqtt().connected() before publishing
• Event-driven sensors: publish on state change
• Periodic sensors: track lastPublishAt with millis()

See Also

• 📡 MQTT Protocol — full topic and payload reference
• 🧬 SmartHomeCore — library API