SURE ProEd (SURE Trust) - Skill Upgradation for Rural-youth Empowerment Trust

G3 Integerated VLSI

Baladitya.P~G3 Integrated

FPGA Vending Machine Controller

Domain: 🖥️ VLSI Design / 🧮 FPGA Development
Technology: 🔌 Verilog
Compliance: 📜 APB Protocol

📋 Table of Contents

1. 🚀 Introduction
2. ✨ Key Features
3. 📊 Visual Documentation
4. 🏛️ System Architecture
5. 🔌 Interface Specifications
6. ⚙️ Configuration Protocol
7. 📈 Results & Validation
8. 🔮 Future Scope

🚀 Introduction

This repository contains a production-grade 🎛️ Verilog implementation of a vending machine controller IP core with:

• ⏱️ Multi-clock domain operation:
  • 100MHz system clock (±50ppm stability)
  • 50MHz APB configuration interface
  • 10KHz-50MHz asynchronous currency input
• 📦 1024-item inventory management
• 💰 Six currency denomination support with smart change calculation
• 🔒 Built-in error handling mechanisms

✨ Key Features

🎯 Core Specifications

Feature	Specification	Notes
📶 Max Items	1024	Parameterized via MAX_ITEMS
💵 Max Currency	100 units	Configurable with MAX_CURRENCY
⚡ Transaction Latency	<10 clock cycles	Worst-case scenario
🔢 Supported Denominations	5, 10, 15, 20, 50, 100	Hard-coded in FSM

🛡️ Reliability Features

• 🧊 Metastability-protected inputs (2-stage synchronizers)
• 🔄 Automatic inventory reconciliation
• 🚨 Immediate refund for:
  • Invalid currency (non-standard denominations)
  • Out-of-stock items
  • Configuration errors

📊 Visual Documentation

🏗️ Block Diagram

⏱️ Timing Diagrams

🏛️ System Architecture

Finite State Machine

State Code	Mode	Description
00	RESET	Initialization state, all registers cleared
01	CONFIG	APB interface active for inventory setup
10	OPERATION	Normal vending machine operation

🔌 Interface Specifications

🎛️ Control Ports

Signal	Type	Width	Description
clk	Input	1b	100MHz ±50ppm
rstn	Input	1b	Async active-low reset
cfg_mode	Input	1b	Config/operation mode select

💰 Currency Interface

Signal	Direction	Timing	Description
currency_valid	Input	10KHz-50MHz	Single-cycle pulse
currency_value	Input	7b	Encoded denomination

🛒 Item Interface

Signal	Direction	Condition	Description
item_select	Input	Operation mode	10-bit encoded product ID
item_select_valid	Input	Operation mode	Selection validation pulse

📝 APB Configuration

Signal	Width	Direction	Description
paddr	15b	Input	Register address
pwdata	32b	Input	Write data
prdata	32b	Output	Read data
pready	1b	Output	Transfer ready

⚙️ Configuration Protocol

Memory Map

Address Range	Register	Access	Description
0x4000_0000	CFG_CTRL	RW	Global control
0x4000_0004	ITEM_0	RW	First item config
...	...	...	...
0x4000_0FFC	ITEM_1023	RW	Last item config

Register Format

Bits	Field	Type	Description
31-24	DISPENSED	RO	Items sold count
23-16	AVAILABLE	RW	Current stock
15-0	PRICE	RW	Item value

📈 Results & Validation

✅ Test Cases

Scenario	Input	Expected Output	Results
Exact Payment	Item5 (20) + 20	Dispense5 + 0	✔️
Overpayment	Item3 (15) + 20	Dispense3 + 5	✔️
Out-of-Stock	Item10 (0) + 50	Empty(1023) + 50	❌
Invalid Currency	Item2 + 13	Empty(1023) + 13	❌

📊 Simulation Outputs

📦 Test Plan

💰 Results

🔮 Future Scope

• 🏧 NFC/RFID interface
• 📱 Remote inventory monitoring
• 💹 Dynamic pricing engine