ESP8266 DHT Logger

Overview

This project is a modular, configurable temperature and humidity logger using the ESP8266MOD (NodeMCU v3) and a DHT11 sensor. It transmits sensor data over Wi-Fi to a remote PHP-based server endpoint using HTTP POST requests. The system follows the MVC2 architectural pattern and includes configuration management, buffer logic, secure payload signing, and real-time performance monitoring.

Features

• Modular architecture with separation of concerns
• JSON-based configuration files stored in SPIFFS
• NTP-synchronized timestamp generation in ISO 8601 format
• Smart buffering and caching system with retry logic
• Configurable sensor read intervals and transmission frequencies
• Real-time status and diagnostic logs via serial monitor
• Payload authentication using HMAC-SHA256
• Network resilience with auto-reconnection
• Configurable buffer limits and performance metrics
• Secure transmission via HTTPS

Configuration Files

BootConfig.json

Contains static configuration used at startup.

{
  "system": {
    "device_id": "ESP8266_DHT_001",
    "firmware_version": "2.0.0",
    "debug_level": 2
  },
  "wifi": {
    "ssid": "YourSSID",
    "password": "YourPassword"
  },
  "sensor": {
    "type": "DHT11",
    "pin": 2,
    "read_interval": 3000
  },
  "location": {
    "latitude": 28.637270,
    "longitude": 77.170277,
    "timezone_offset": 19800
  }
}

config.json Contains runtime-configurable parameters.

{
  "transmission": {
    "interval": 5000,
    "server_url": "https://yourdomain.com/controller.php",
    "timeout": 15000,
    "retry_attempts": 3
  },
  "buffer": {
    "max_size": 50,
    "cache_duration": 300000
  },
  "security": {
    "secret_key": "your-secret-key",
    "enable_encryption": false,
    "signature_algorithm": "HMAC-SHA256"
  }
}

How It Works

• DHT11 sensor collects temperature and humidity data.
• Timestamp is synchronized via NTP (UTC +5:30 IST offset).
• Data is pushed to a buffer with time-based aging and size constraints.
• Valid sensor packets are converted to signed JSON and sent to a PHP server.
• Failed transmissions are retried based on configuration.
• Buffer management handles overflows and cache expiry.

Setup Requirements

• Arduino IDE with ESP8266 board support

Required Libraries:

• ESP8266WiFi

• ESP8266HTTPClient

• WiFiClientSecure

• ArduinoJson

• DHT

• NTPClient

• SPIFFS

• An HTTPS-capable PHP endpoint to receive POST requests

Notes

• Sensor reads every read_interval ms; transmission every transmission.interval ms.
• Cached readings are retried with exponential backoff and aging-based eviction.
• JSON payload includes metrics like heap size, RSSI, and uptime.

License

This project is intended for academic and prototyping use. Commercial usage requires explicit permission.