Debounce a Push Button in Software

Understand the target result

Prevent one physical press from being interpreted as several presses. The expected result is: One press creates one clean event even when the contacts bounce.

Prepare the board and parts

Disconnect the ESP32 from USB. Put the ESP32, breadboard, jumper wires, and the listed lesson parts in front of you. Straighten bent pins gently and never force a module into the breadboard.

Make each connection with power off

1. Connect one side of the push button to GPIO 4.
2. Connect the opposite side to GND.
3. The code uses INPUT_PULLUP, so no external pull-up resistor is required.

Install any library and upload the code

No additional Arduino library is required for this starter sketch. Select your ESP32 board and serial port before clicking Upload.

const int BUTTON = 4;
bool stableState = HIGH, lastReading = HIGH;
unsigned long changedAt = 0;
void setup() { Serial.begin(115200); pinMode(BUTTON, INPUT_PULLUP); }
void loop() {
  bool reading = digitalRead(BUTTON);
  if (reading != lastReading) changedAt = millis();
  if (millis() - changedAt > 40 && reading != stableState) {
    stableState = reading;
    if (stableState == LOW) Serial.println("One clean press");
  }
  lastReading = reading;
}

Power the circuit and observe

Connect USB power only after the wiring check. Open Serial Monitor at 115200 baud when the sketch prints data. Watch the circuit for at least 20 seconds and compare it with this expected behavior: One press creates one clean event even when the contacts bounce.

Change one value and test again

Make one small change—such as a delay, threshold, brightness, or displayed message—then upload again. This confirms that you understand which part of the program controls the result.