🌪️ ESP32-Based Disaster Management Audio Alert System

This project is a disaster warning system built using ESP32 microcontrollers. It enables government authorities to wirelessly transmit audio alerts (via nRF24L01 modules) to people during emergency situations such as natural disasters.

📡 Project Overview

• 🧠 Transmitter ESP32: Connects to a Wi-Fi hotspot, receives MP3 files from a web UI, converts them to RAW format using a Node.js server, and transmits the audio via nRF24L01.
• 🎧 Receiver ESP32: Listens for audio data over nRF24L01, stores the data in LittleFS, and plays it using a MAX98357 I2S DAC amplifier.

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🔌 Hardware Used

Transmitter Node:

• ESP32 Dev Board
• nRF24L01+ PA+LNA Module
• Wi-Fi Hotspot (e.g., mobile)
• Node.js-capable laptop for audio conversion

Receiver Node:

• ESP32 Dev Board
• nRF24L01+ Module
• MAX98357 I2S DAC Amplifier
• Speaker

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🪛 Pin Configuration

Transmitter (nRF24L01):

• CE: GPIO 4
• CSN: GPIO 5
• SPI:
  • MOSI: GPIO 23
  • MISO: GPIO 19
  • SCK: GPIO 18

Receiver:

• Same SPI configuration as above
• I2S (MAX98357):
  • BCLK: GPIO 26
  • LRCK: GPIO 25
  • DIN: GPIO 22

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🖼️ Web Interface

The transmitter ESP32 hosts a web UI that allows users to upload .mp3 files.

⚠️ Upload Instructions

1. Compile and build the React-based frontend using Vite.
2. Upload the resulting dist/ folder to the transmitter ESP32 using LittleFS Data Upload Tool.

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🧩 MP3 to RAW Conversion (Local Server)

🛠️ Node.js + FFmpeg Setup

This project includes a local server that uses FFmpeg via Node.js + Express to convert uploaded MP3 files to .raw format for playback on the receiver.

📁 Location in Repo

The code for the converter is located in the converter/ directory of this project:

converter/
├── index.js
├── package.json
├── package-lock.json
└── uploads/

🚀 How to Run

1. Open a terminal inside the converter/ directory.
2. Install dependencies:

npm install

3. Start the server:

node index.js

The server will listen on http://<your-laptop-ip>:3000/convert.

🔧 Important:
Update the ESP32 transmitter code with your laptop’s IP address to ensure it can POST the MP3 to your machine.

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🧪 How It Works

1. User uploads .mp3 file via the ESP32-hosted webpage.
2. The file is POSTed to the Node.js server running on your laptop.
3. The server converts it using FFmpeg and returns .raw audio data.
4. ESP32 saves it to LittleFS as audio.raw.
5. Audio is sent chunk-by-chunk (32 bytes) over nRF24L01 to receivers.
6. Receivers store the file and play it via I2S DAC to a speaker.

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📂 File Structure

project-root/
├── converter/         # Node.js + FFmpeg converter
├── ui/                # Web UI (build with Vite)
├── data/              # LittleFS image folder
├── transmitter.ino    # Main ESP32 transmitter firmware
└── receiver.ino       # Main ESP32 receiver firmware

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📦 Dependencies

• ESP32 Arduino Core
• nRF24L01 Radio Library
• LittleFS
• MAX98357 I2S Audio DAC

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📢 Contribution

Pull requests and improvements welcome! If you’re looking to extend this for other forms of alert or with different communication modules (LoRa, WiFi Mesh, etc.), go for it!

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🛡️ License

MIT License