{
  "topic": "zenith/node-01/esp32",
  "timestamp_utc": 1787063965,
  "telemetry": {
    "device": "ESP32-WROOM-32D",
    "core": "Xtensa-LX6-DualCore",
    "cpu_freq_mhz": 240,
    "free_heap_kb": 284,
    "wifi_rssi_dbm": -58,
    "status": "SYSTEM_NOMINAL"
  }
}

// ESP32 System Telemetry Node
#include <WiFi.h>
#include <PubSubClient.h>

void publishTelemetry() {
  uint32_t freeHeap = ESP.getFreeHeap() / 1024;
  int8_t rssi = WiFi.RSSI();
  
  StaticJsonDocument<128> doc;
  doc["cpu_freq_mhz"] = getCpuFrequencyMhz();
  doc["free_heap_kb"] = freeHeap;
  doc["wifi_rssi_dbm"] = rssi;
  
  char buffer[128];
  serializeJson(doc, buffer);
  mqttClient.publish("zenith/esp32/status", buffer);
}