Button Input: Debouncing, State Machines, and Type Safety

Buttons are harder than LEDs—hardware bounce, non-blocking debouncing, state machines, plus type-safe refactoring in C++.

Motivation

• Part 19: From Output to Input — Why buttons are harder than LEDs

Hardware Fundamentals

• Part 20: GPIO Input Mode Internal Circuits — How the chip "hears" external signals
• Part 21: Button Circuits and Mechanical Bounce — What real-world signals look like

HAL and Polling

• Part 22: HAL GPIO Input API — How to read button states in code
• Part 23: Polling Buttons in C — First hands-on: controlling an LED with a button

Debouncing

• Part 24: Non-blocking Debounce — Don't make the CPU wait
• Part 25: 7-State Debounce State Machine — The core of this series

C++ Refactoring Evolution

• Part 26: Refactoring Button Code with enum class — Type-safe input
• Part 27: Events + std::variant Dispatch — Type-safe "what happened"
• Part 28: Button Template Class Design — Let the compiler do the work
• Part 29: Constraining Callbacks with Concepts — Complete code walkthrough

Interrupts and Summary

• Part 30: EXTI Interrupts — Pitfalls and exercises