Internal Pull-Up and Pull-Down

The ESP32 has built-in pull-up and pull-down resistors, which can be enabled in software using the pinMode() function. The resistance values for the internal pull-up and pull-down resistors in the ESP32 are approximately 45kΩ. These internal resistors are useful when you need a simple way to ensure a default state (either HIGH or LOW) for a GPIO pin, without needing to add external resistors.

Enabling internal pull-up resistor:

pinMode(GPIO_PIN, INPUT_PULLUP);

Enabling internal pull-down resistor:

pinMode(GPIO_PIN, INPUT_PULLDOWN);

Basic Arduino Code

This example configures GPIO 22 as an input, using the internal pull-up resistor.

#define BUTTON_PIN 22 // Define the GPIO pin connected to the button

void setup() {
  Serial.begin(115200); // Initialize serial communication
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Configure pin 22 as input with internal pull-up resistor
}

void loop() {
  // Read the button state
  int buttonState = digitalRead(BUTTON_PIN);

  if (buttonState == LOW) {
    // Button is pressed
    Serial.println("Button Pressed");
  } else {
    // Button is not pressed
    Serial.println("Button Released");
  }

  delay(100); // Small delay for debounce
}