ESP32 Weather Station

A feature-rich IoT weather station built on the ESP32 microcontroller using ESP-IDF (Espressif IoT Development Framework) and FreeRTOS. This project monitors temperature and humidity via a DHT22 sensor, provides a web interface for configuration and monitoring, and publishes sensor data to AWS IoT Core via MQTT.

Features

Core Functionality

• DHT22 Temperature & Humidity Monitoring - Reads environmental data from DHT22 sensor
• WiFi Connectivity - Dual-mode operation (Access Point + Station mode)
• Web-Based Configuration - HTTP server with responsive web interface for device setup
• AWS IoT Integration - Publishes sensor data to AWS IoT Core using MQTT protocol
• OTA Firmware Updates - Upload new firmware over-the-air via web interface
• RGB LED Status Indicators - Visual feedback for connection status and states
• WiFi Reset Button - Hardware button with interrupt-based WiFi credential reset

Advanced Features

• Non-Volatile Storage (NVS) - Persistent storage of WiFi credentials
• SNTP Time Synchronization - Automatic network time sync for timestamped data
• Dual-Core Utilization - Optimized task distribution across both ESP32 cores
• FreeRTOS Task Management - Multi-threaded architecture with message queues and semaphores
• State Machine Design - Robust WiFi connection management with retry logic

Hardware Requirements

• ESP32 Development Board (any ESP32 DevKit)
• DHT22 Temperature/Humidity Sensor
• RGB LED (common cathode or anode with appropriate resistors)
• Push Button (for WiFi reset functionality)
• Resistors (220Ω-330Ω for LED current limiting)
• Breadboard and Jumper Wires

Default GPIO Pin Configuration

DHT22 Sensor:     GPIO 25
RGB LED Red:      GPIO 21
RGB LED Green:    GPIO 22
RGB LED Blue:     GPIO 23
Reset Button:     (Configure in wifi_reset_button.c)

Software Requirements

• ESP-IDF v4.4 or later (Espressif IoT Development Framework)
• CMake (version 3.5 or later)
• Python 3.x (for ESP-IDF build tools)
• AWS Account (for AWS IoT Core connectivity)
• Web Browser (Chrome/Firefox recommended for web interface)

Installation & Setup

Configure AWS IoT Credentials

Create a main/certs/ directory and add your AWS IoT certificates:

mkdir -p main/certs

Place the following files in main/certs/:

• aws_root_ca_pem - Amazon Root CA certificate
• certificate_pem_crt - Device certificate
• private_pem_key - Private key

Note: These certificate files are gitignored for security.

Configure Project Settings

Edit main/aws_iot.h to set your AWS IoT client ID:

#define CONFIG_AWS_EXAMPLE_CLIENT_ID "Your_ESP32_Client_ID"

Optionally modify WiFi AP settings in main/wifi_app.h:

#define WIFI_AP_SSID         "ESP32_AP"
#define WIFI_AP_PASSWORD     "password"

5. Build and Flash

# Set ESP-IDF environment variables
. $HOME/esp/esp-idf/export.sh

# Build the project
idf.py build

# Flash to ESP32 (replace PORT with your serial port)
idf.py -p PORT flash monitor

Usage

Initial Setup

1. Power on the ESP32 - The RGB LED will indicate status
2. Connect to ESP32 Access Point - Look for WiFi network "ESP32_AP" (password: "password")
3. Open Web Interface - Navigate to http://192.168.0.1 in your browser
4. Configure WiFi - Enter your home/office WiFi credentials through the web interface
5. Connect - ESP32 will connect to your WiFi network and begin operation

Web Interface Features

• WiFi Configuration - Connect ESP32 to your wireless network
• Connection Status - View current WiFi connection details and signal strength (RSSI)
• Sensor Data - Real-time temperature and humidity readings
• Time Display - Synchronized network time
• OTA Updates - Upload new firmware binaries for wireless updates
• WiFi Disconnect - Manually disconnect from current network

AWS IoT Integration

Once connected to WiFi, the device will:

• Connect to AWS IoT Core using MQTT over TLS
• Publish sensor data (temperature, humidity, RSSI) to configured topics
• Subscribe to command topics for remote control

Project Structure

weather_station/
├── main/
│   ├── main.c                  # Application entry point
│   ├── wifi_app.c/h            # WiFi application and state machine
│   ├── http_server.c/h         # HTTP server implementation
│   ├── aws_iot.c/h             # AWS IoT MQTT client
│   ├── DHT22.c/h               # DHT22 sensor driver
│   ├── rgb_led.c/h             # RGB LED control
│   ├── app_nvs.c/h             # Non-volatile storage management
│   ├── sntp_time_sync.c/h      # SNTP time synchronization
│   ├── wifi_reset_button.c/h   # Reset button with ISR
│   ├── tasks_common.h          # FreeRTOS task configuration
│   ├── webpage/                # Web interface files
│   │   ├── index.html
│   │   ├── app.js
│   │   ├── app.css
│   │   └── jquery-3.3.1.min.js
│   └── certs/                  # AWS IoT certificates (gitignored)
├── CMakeLists.txt              # Root CMake configuration
├── partitions.csv              # Custom partition table for OTA
└── README.md

Architecture

FreeRTOS Task Distribution

Core 0:

• WiFi Application Task
• HTTP Server Task
• HTTP Server Monitor Task
• WiFi Reset Button Task

Core 1:

• DHT22 Sensor Task
• SNTP Time Sync Task
• AWS IoT Task

Communication

• Message Queues - Inter-task communication for WiFi events and HTTP server messages
• Event Groups - WiFi connection synchronization
• Binary Semaphores - ISR signaling from hardware button

Troubleshooting

WiFi Connection Issues

• Verify SSID and password are correct
• Check WiFi signal strength
• Press and hold the reset button to clear stored credentials

AWS IoT Connection Failures

• Verify certificates are correctly placed in main/certs/
• Check AWS IoT thing name and endpoint configuration
• Ensure device certificate is activated in AWS IoT console

OTA Update Failures

• Ensure firmware binary is built for OTA partitions
• Check that new firmware size fits within partition size (1984KB)