RFID Wallet Transaction System

A real-time RFID-based wallet system featuring an ESP8266 reader, a Node.js backend, SQLite database integration, and a live web dashboard with separate Admin (Top-Up) and Cashier (Payment) interfaces.

🔗 Live Dashboard: http://157.173.101.159:8021/

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🚀 Overview

This project implements a complete RFID Wallet Transaction System that enables:

• Card Top-Up (Credit)
• Product Payment (Debit)
• Real-time balance updates
• Safe wallet updates (atomic transactions)
• Strict MQTT topic isolation

Users scan RFID cards using an ESP8266 terminal. The backend processes transactions securely and updates the web dashboard instantly via WebSocket.

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🏗️ Architecture

The system consists of three main components:

1️⃣ ESP8266 (Firmware / Hardware)

• Scans RFID cards using an MFRC522 reader
• Publishes card UID and balance via MQTT
• Subscribes to:
  • Top-Up commands
  • Payment commands
• Updates local balance
• Publishes updated balance confirmation

Important:

• Does NOT use HTTP
• Does NOT use WebSocket

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2️⃣ Node.js Backend (API + MQTT Bridge)

• Express.js REST API
• MQTT client (Publish–Subscribe communication)
• Socket.io for real-time updates
• SQLite database for transaction integrity

API Endpoints

• POST /topup
• POST /pay

Responsibilities

• Business logic processing
• Balance validation
• Safe wallet update (atomic database transaction)
• MQTT message translation
• Real-time WebSocket updates to dashboard

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3️⃣ Web Dashboard (Frontend)

Responsive web interface built with Vanilla JS.

🟢 Admin Interface (Top-Up)

• Auto-detected Card UID
• Previous balance display
• Top-up amount input
• “TOP UP” button
• Success/Fail response
• Real-time updated balance

🔵 Cashier Interface (Payment)

• Auto-detected Card UID
• Previous balance display
• Product dropdown selection
• Quantity input
• Auto-calculated total cost
• “PAY” button
• Approved/Declined result with reason
• Real-time updated balance

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📂 Project Structure

• Backend/ – Node.js server, API routes, MQTT logic, database integration
• Frontend/ – Web dashboard interface
• ESP8266/ – Arduino source code (RFDI.ino)
• database/ – SQLite database file

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🛠️ Setup & Installation

Backend Setup

cd Backend
npm install
npm start

Server runs on:

http://localhost:3000

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ESP8266 Configuration

Open ESP8266/RFDI.ino in Arduino IDE and update:

#define WIFI_SSID "Your_SSID"
#define WIFI_PASS "Your_Password"

Flash the code to your ESP8266 board.

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🔌 Hardware Wiring (MFRC522 ↔ ESP8266 NodeMCU)

MFRC522 Pin	ESP8266 Pin	Notes
VCC	3.3V	Do NOT use 5V
GND	GND	Ground reference
RST	GPIO0 (D3)	Reset pin
NSS/CS	GPIO2 (D4)	SPI Select
MOSI	GPIO13 (D7)	SPI MOSI
MISO	GPIO12 (D6)	SPI MISO
SCK	GPIO14 (D5)	SPI Clock

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📡 MQTT Topic Namespace

Base topic:

rfid/y2c_team0125/

Topics Used

• rfid/y2c_team0125/card/status
• rfid/y2c_team0125/card/topup
• rfid/y2c_team0125/card/pay
• rfid/y2c_team0125/card/balance

No wildcard subscriptions.
No generic topics.
Strict team isolation enforced.

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🗄️ Database Design (SQLite)

The system uses SQLite to ensure safe and atomic wallet operations.

Tables

• Cards
• Wallet
• Products
• Transactions (Ledger)

Each transaction stores:

• Transaction type (TOPUP / PAYMENT)
• Previous balance
• New balance
• Timestamp

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🔒 Safe Wallet Update (Atomic Transaction)

All wallet operations follow:

1. BEGIN TRANSACTION
2. Validate balance (for payments)
3. Update wallet balance
4. Insert transaction record
5. COMMIT

If any step fails:

ROLLBACK

This guarantees:

• No partial updates
• No double spending
• No inconsistent balances
• Full transaction integrity

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🔁 Communication Flow

Card Scan

ESP → MQTT → Backend → WebSocket → Dashboard

Top-Up

Dashboard → HTTP → Backend → MQTT → ESP
ESP → MQTT → Backend → WebSocket → Dashboard

Payment

Dashboard → HTTP → Backend
Backend validates balance → Safe DB update → MQTT command to ESP
ESP confirms → WebSocket update to dashboard

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🌍 Deployment

• Backend deployed on VPS
• Public dashboard accessible online
• Repository is public and structured

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📜 License

Licensed under the ISC License.