🛠 Lire un bouton poussoir avec anti-rebond

Objectives

Learn digital input reading on the ESP32-S2: enable an internal pull-up resistor, read the state of a button, and filter mechanical bouncing using a software delay.

Hardware

• ESP32-S2 board
• 1 push button
• 1 LED with a 330 Ω resistor (optional, for the indicator)
• Dupont cables

Full code

// Bouton avec anti-rebond logiciel sur ESP32-S2
const uint8_t BTN_PIN = 4;
const uint8_t LED_PIN = 2;
const unsigned long DEBOUNCE_MS = 50;

bool etatLed = false;
bool dernierEtatBtn = HIGH;
unsigned long dernierBordMs = 0;

void setup {
  pinMode(BTN_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(115200);
}

void loop {
  bool etatBtn = digitalRead(BTN_PIN);
  unsigned long maintenant = millis;
  if (etatBtn != dernierEtatBtn &&
      maintenant - dernierBordMs >= DEBOUNCE_MS) {
    dernierBordMs = maintenant;
    dernierEtatBtn = etatBtn;
    if (etatBtn == LOW) {          // bouton enfoncé (logique inversée)
      etatLed = !etatLed;
      digitalWrite(LED_PIN, etatLed ? HIGH : LOW);
      Serial.println(etatLed ? "LED ON" : "LED OFF");
    }
  }
}

Expected verification

Each press of the button toggles the LED and displays "LED ON" or "LED OFF" on the serial monitor at 115200 bauds. A single firm press results in only one state change.

Common errors

• Forgetting INPUT_PULLUP: the input floats and the state changes without pressing the button.
• Misunderstanding inverted logic: with a pull-up, the GPIO reads LOW when the button is pressed.
• Debounce time too short: some presses are counted twice; increase DEBOUNCE_MS.
• Button wired to a pin occupied by flash or PSRAM: consult the board schematic before choosing the pin.