ESP32-C3 button

// Button: a pushbutton on GPIO 9 lights the LED on GPIO 8.
//
// INPUT_PULLUP switches on the pad's 45 k pull-up, so the pin sits at 3.3 V
// until the button pulls it to GND. That is why the button reads LOW when it
// is pressed: wire one side to GPIO 9 and the other to GND, no resistor.

const int BUTTON_PIN = 9;

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  bool pressed = digitalRead(BUTTON_PIN) == LOW;
  digitalWrite(LED_BUILTIN, pressed ? HIGH : LOW);
  delay(5);
}