Smart Farm IoT: Distributed Garden Watering System

Context and Motivation

Agriculture faces significant challenges in optimizing resources and ensuring sustainability. Traditional farming methods often lead to inefficient water usage, delayed responses to environmental changes, and difficulty in monitoring large areas. The integration of IoT and distributed systems offers a transformative solution by enabling real-time monitoring, automated control, and data-driven decision-making.

Project Vision

The goal is to create a modular smart agricultural system integrating solar modules, weather monitoring, water management, distributed IoT nodes, a central gateway, backend infrastructure, and a frontend interface. The system makes farms more productive, sustainable, and easier to manage.

Current Scope

This PoC validates the core architecture with data collection nodes (Arduino Nano, DHT11, soil moisture sensors), secure ESP32 gateway with LoRa and SSL/TLS, and Java server with Kafka integration.

ESP32 Gateway

Dual-core 32-bit Tensilica LX6 at 240 MHz with 520 KB SRAM. Parallel processing: one core handles LoRa, the other manages Wi-Fi. Built-in Wi-Fi 802.11 b/g/n with WPA2 and SSL/TLS support.

LoRa Communication

433 MHz frequency enables 10 km range vs Wi-Fi's 100m. Chirp Spread Spectrum provides noise immunity and simultaneous multi-node communication. Only 120 mA max during transmission, enabling months of battery operation.

Arduino Nano

ATmega328P at 16 MHz with 2 KB SRAM. 19 mA active, reducible to microamps in sleep mode for long-term battery deployment.

Sensors

DHT11: 0-50°C (±2°C), 20-90% RH (±5%), 2.5 mA. Capacitive soil moisture: corrosion-resistant, analog output for fine-grained measurements.

Node Architecture

Independent read-transmit-sleep cycle. Reads DHT11 and soil moisture, formats as ID:T1 T:25.0 H:60.0 S:450, transmits via LoRa.

Key Features

Bidirectional communication with STOP command for low-power mode. LowPower library reduces 19 mA to 5 μA during sleep, extending battery life from days to months.

Hardware

LoRa via SPI (pins 11, 12, 13, 10, 9, 2). DHT11 on digital pin 2 with 10kΩ pull-up. Soil moisture on A0 with power cycling to prevent electrolysis.

Gateway Role

Bridges LoRa sensor network and cloud. Receives from multiple nodes, validates, aggregates, and securely transmits via SSL/TLS. Relays commands back to nodes.

Core Functionality

Wi-Fi with auto-reconnect and exponential backoff. TLS-encrypted server connections. Interrupt-driven LoRa reception with RSSI monitoring. Data validation before forwarding.

Network

Communicates via orman-nodes.duckdns.org (DuckDNS for static DNS). Port 12345 forwarded to server's local IP. LoRa on GPIO 23, 19, 18, 5, 14, 26.

Server Architecture

Central hub for data processing. Receives via SSL/TLS, validates with regex, forwards to Kafka for distributed analytics. Handles multiple simultaneous gateways.

Infrastructure

DuckDNS maps orman-nodes.duckdns.org to public IP. Port 12345 forwarded to internal IP. SSL/TLS via Java Keystore (JKS).

Data Pipeline

Regex validation: ID:[a-zA-Z0-9]+ T:[+-]?\d+(\.\d+)? H:[+-]?\d+(\.\d+)? S:\d+ RSSI:[+-]?\d+. JSON conversion via Jackson. Kafka publish to 'iot-data' topic.

Kafka Benefits

Decoupling, scalability, reliability (data persistence), real-time stream processing. PSK authentication with future certificate-based mutual TLS.