ESP32 GPIP Inputs
Fromp;     https://microcontrollerslab.com/push-button-esp32-gpio-digital-input/ 




Push button with ESP32 – GPIO pins as digital input

Push button with ESP32 – GPIO pins as digital input, In this fifth tutorial on 
a series of ESP32 tutorials, we will teach you how to use GPIO pins of ESP32 as 
digital input pins and how to interface a push button with the ESP32 development
board. The push button is used to control device like turning on and off a light
emitting diode when the push button is pressed or not. Similarly, we can use 
push button to increase or decrease speed of dc motor. When you use push button 
with ESP32, we have to use GPIO pins as digital input pins. Because we will read
the state of the push button. The push button will give two logical states 
either high or low.

In the last tutorial, we have learned how to use GPIO pins of ESP32 as digital 
output pins by creating an LED blinking example:

GPIO pins of ESP32 – LED Blinking example

We have a similar guide with MicroPython:

ESP32 and ESP8266 GPIO Programming with MicroPython – LED Blinking Example


Push Button Interfacing Configurations



There are two configuration modes to interface a push button with ESP32 board. Let’s discuss both these modes one by one.


Pull-Up Mode



In Pull-up mode, when a push button is not pressed, a logic high input appears 
on the ESP32 GPIO pin. Because a 5V signal appears on the input terminal through
an R1 resistor. On the contrary, when the push button is pressed, metallic 
contacts of the push button make contact with the ground terminal and the input 
terminal. Therefore, a logic low input reflects on the digital input pin of the 
ESP32 board. In short, by reading this state of the push button with a digital 
input pin of a microcontroller, we can identify whether a push button is pressed
or not. The following schematic diagram shows the connection of a push button 
with a pull-up resistor. 


Schematic Pullup resistor STM32F4


Pull-Down Mode



In Pull-down mode, when a push button is not pressed, a logic low input appears 
on the ESP32 GPIO pin. Because a ground reference signal appears on the input 
terminal through an R1 resistor. On the contrary, when the push button is 
pressed, metallic contacts of the push button make contact with the +5V signal 
and the input terminal. Therefore, a logic high input reflects on the digital 
input pin of ESP32 board. The following schematic diagram shows the connection 
of a push button with a pull-up resistor.


Pull down resistor with Push button Schematic


Push button interfacing with ESP32




So We will use digital input pin of ESP32 development board to read this logical
and logical low state using pinMode function of Arduino IDE.  So now let’s start
with a circuit diagram of push button interfacing with esp32 and after that I 
will explain the programming part.

If you are a beginner and do not have an idea about ESP32 development board, you
can check this guide:

    Getting started with the ESP32 development board 

Arduino IDE is used to program ESP32 in these series of tutorial and we can 
install ESP32 board in Arduino IDE. You can check this tutorial:



    How to install ESP32 library in Arduino IDE

Push button and LED ESP32

So now let’s perform a simple example to connect a push button with any GPIO pin
and turn on an LED connected to another digital pin. 

As shown in the above pinout, we will be using GPIO15 to connect the push button
and GPIO22 to connect a push button. We can use any GPIO pin either as digital 
input or digital output pins except few GPIO pins which can be used only as 
digital input pins for more information about it check ESP32 pin out the 
tutorial.

Circuit diagram of Push button with ESP32



Schematic is for push button interfacing is shown below:

Push button interfacing with ESP32



Code



Code for push button interfacing is given below. All the functions used in this 
code the same as used in the last tutorial on LED blinking except one function 
digitalRead function. So I will explain digital read function now:

digitalRead(Pin_number): Digital read function is used to read the state of the 
input pin. This digitalRead function returns either logical HIGH or logical LOW 
input. If input state of the pin is HIGH, it will return HIGH and otherwise low.
You only need to pass pin number as a augment to this function. For example in 
this tutorial, we are using pin number 15 as a digital input, so we will use 
this function like this digitalRead(22) or we can define 22 with any name and 
use name instead of pin number as we did in the example code below:


/*F********************************************************************
*
**********************************************************************/
const int LEDPIN = 22;           // ASSIGNED A NAME LED PIN TO PIN NUMBER 22
const int PushButton // THIS WILL ASSIGN THE NAME pUSHbUTTON TO PIN NUMER 15

/*F********************************************************************
* THIS sETUP FUNCTION IS USED TO INITIALIZE EVERYTHING 
**********************************************************************/
void 
setup()
{
	pinMode( LEDPIN, OUTPUT );           // DECLARE PIN 22 AS DIGITAL OUTPUT
	pinMode( PushButton, INPUT );         // DECLARE PIN 15 AS DIGITAL INPUT 
}
/*F********************************************************************
*
**********************************************************************/
void 
loop()
{
	// STORE PUSH BUTTON STATE IN VAR PUSH_BUTTON_STATE
	int push_button_state = digitalRead( PushButton );
	if ( push_button_state == HIGH )      // CHECK IF PUSH BUTTON IS PRESSED
		digitalWrite( LEDPIN, HIGH ); // PRESSED LED ON OTHERWISE REMAIN OFF
	else 
		digitalWrite( LEDPIN, LOW ); 
}

So this is the simple code used to read the state of push button or any switch. 
So let’s see how the code works?