Internet of Things (IoT)

Four-tier IoT architecture:

1. Perception Layer Physical sensors and actuators
2. - Temperature, humidity, motion, pressure sensors
3. - Microcontrollers: Arduino, ESP32, Raspberry Pi
4. - Communication: Bluetooth LE, Zigbee, Z-Wave (short range)

1. Network Layer Connectivity protocols
2. - WiFi (high bandwidth, high power)
3. - LoRaWAN (long range, low power km range)
4. - NB-IoT / LTE-M (cellular, wide coverage)
5. - MQTT: lightweight pub/sub over TCP (port 1883)
6. - CoAP: REST-like for constrained devices (UDP)

1. Processing Layer Edge and cloud compute
2. - Edge computing: process locally, reduce latency
3. - AWS IoT Core, Azure IoT Hub, Google Cloud IoT
4. - Time-series databases: InfluxDB, TimescaleDB

1. Application Layer Dashboards, automation, AI
2. - Real-time dashboards: Grafana, Kibana
3. - Automation rules and alerts
4. - ML on edge: TensorFlow Lite, Edge Impulse

// Arduino with ESP32 publish sensor data via MQTT
#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>

WiFiClient wifi; PubSubClient mqtt(wifi); DHT dht(4, DHT22);

void setup() { WiFi.begin("SSID", "PASSWORD"); while (WiFi.status() != WL_CONNECTED) delay(500); mqtt.setServer("broker.hivemq.com", 1883); mqtt.connect("esp32-sensor-01"); dht.begin(); }

void loop() { float temp = dht.readTemperature(); float humidity = dht.readHumidity(); char payload[100]; sprintf(payload, '{"temp":%.1f,"humidity":%.1f}', temp, humidity); mqtt.publish("sensors/room-1/climate", payload); delay(5000); } ```