🔘 GPIO Inputs

Why it matters

A real button press should be one event. Without debouncing you get phantom presses, double-clicks, and flaky menus — even with perfect code everywhere else.

The idea

Goal

Turn a noisy mechanical switch into a clean digital signal you can trust.

        <h3>What's actually happening</h3>
        A switch is two pieces of metal touching. When they first touch, they bounce for a few milliseconds:
        HIGH/LOW/HIGH/LOW… then finally settle. Your CPU is fast enough to see all those transitions.

        <div class=

Demo

The top timeline is the raw GPIO signal (with bounce). The bottom is the debounced output.

Use:

• Bounce Severity: how

  Key takeaways

  • Mechanical switches bounce for a few milliseconds
  • A floating input will randomly flip — use pull-ups/pull-downs
  • Debouncing is a small state machine: detect change → wait for stability → accept
  • On ESP32, some pins are input-only (34–39) and some are strapping pins (boot-sensitive)

  Going deeper

  Hardware debounce (RC + Schmitt trigger) can reduce CPU work and improve EMI robustness. For event-driven code, interrupts still need debouncing — either by masking interrupts for a window, or by using a timer task to confirm stability.

  Math details

  Definitions:
    sample_rate = N samples / second
    debounce_window = W seconds
  
  Rule of thumb:
    W should be several times the worst-case bounce duration.
  
  Simple debounce state machine:
    if raw != pending:
        pending = raw
        stable_time = 0
    else:
        stable_time += dt
        if stable_time >= W:
            debounced = pending

  Implementation

  LLM Prompt: GPIO Debounce