STM32 LED & Button Control — Register Coding Method

A bare-metal STM32 project that demonstrates LED blink delay control using two push buttons, implemented using direct register access (no HAL GPIO APIs for logic control).

This project focuses on real-world embedded behavior: timing control, input handling, and boundary protection — all at the register level.

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🎯 Project Objective

The goal of this project is to dynamically control LED blink speed using two buttons:

• LED on Pin PA5 (Arduino D13 / Pin 13)
• Button 1 on Pin PA6 (Arduino D12 / Pin 12) → Increase delay
• Button 2 on Pin PA7 (Arduino D11 / Pin 11) → Decrease delay

Functional Behavior

Action	Result
Button-1 pressed	Delay increases by 100 ms
Button-2 pressed	Delay decreases by 100 ms
Delay range	0 ms to 1000 ms
LED behavior	Blinks continuously using current delay

This mimics a human-controlled timing system, a pattern widely used in industrial HMI logic.

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🧠 Why Register-Level Coding?

This project intentionally avoids HAL GPIO logic to help you:

• Understand how GPIO really works
• Gain full control over timing & pin state
• Eliminate abstraction overhead
• Debug hardware with absolute clarity

Everything is driven by:

• RCC->AHB1ENR
• GPIOx->MODER
• GPIOx->IDR
• GPIOx->ODR
• SysTick timing

No magic. No shortcuts.

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🧰 Hardware Mapping

Component	STM32 Pin	Arduino Label
LED	PA5	D13
Button – Increment	PA6	D12
Button – Decrement	PA7	D11

Buttons should use pull-down or pull-up logic (external or internal).

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📦 Repository Structure

STM32-LED-BUTTON-CTRL-Register-Coding-Method/
├── Core/
│   ├── Src/
│   │   └── main.c        # Register-level LED & button logic
│   └── Inc/
│       └── main.h
├── Drivers/
│   └── CMSIS/            # Device headers & startup code
├── startup_stm32f446xx.s
├── STM32F446RETX_FLASH.ld
├── .project
├── .cproject
└── README.md

All logic lives inside main.c.

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⚙️ Core Logic Explained (High Level)

1️⃣ Clock Enable

Enable GPIOA and SysTick clocks using RCC.

2️⃣ GPIO Configuration

• PA5 → Output (LED)
• PA6, PA7 → Input (Buttons)

Configured manually via MODER.

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3️⃣ Delay Control Logic

• Delay variable starts at 500 ms (default)
• Button presses update delay dynamically
• Delay is clamped between 0–1000 ms

if (button_inc_pressed) {
    delay += 100;
}
if (button_dec_pressed) {
    delay -= 100;
}

Boundary protection ensures:

if (delay > 1000) delay = 1000;
if (delay < 0) delay = 0;

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4️⃣ LED Blink

LED toggles continuously using the current delay value:

GPIOA->ODR ^= (1 << 5);
delay_ms(current_delay);

This creates real-time visual feedback based on button input.

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🚀 How to Run

1️⃣ Clone Repo

git clone https://github.com/DanielRajChristeen/STM32-LED-BUTTON-CTRL-Register-Coding-Method.git

2️⃣ Open in STM32CubeIDE

CubeIDE is used only as compiler and debugger

• Import existing project
• Build once

3️⃣ Flash & Test

• Connect board via ST-LINK
• Run / Debug
• Press buttons and watch LED speed change live

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📘 What You’ll Learn

By completing this project, you’ll understand:

• GPIO input & output at register level
• Button-driven control systems
• Timing control using SysTick
• Delay clamping & boundary conditions
• Real-time firmware behavior

This is core embedded thinking, not just coding.

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🧪 Typical Use-Cases

• Beginner-friendly embedded timing demo
• Register-level GPIO practice
• Interview preparation project
• PCB button/LED validation
• Transition step from HAL → Bare-metal

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📜 License — MIT

MIT License

Copyright (c) 2025 Daniel Raj Christeen

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND.

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