ESP32 pinout – How to use GPIO pins?

This tutorial is about pinout of the ESP32 development board, especially for ESP32 devkit. ESP32 devkit consists of ESP-WROOM-32 module.  There are many versions of ESP32 chip available in the market. But ESP32 devkit uses ESP-WROOM-32 module. But the functionality of all GPIO pins is the same across all ESP32 development boards. I find many people searching online about this development board. Many people are asking questions about how to use its GPIO pins? Which GPIO pin can be used as digital input output pin? Which GPIO pin can be used as an analog pin? Which pin should not be used to use this board safely. You will get the answer to these questions in this article. So now let’s begin with the introduction of GPIO pins of the ESP32 development board.

Introduction to ESP32 chip

  • ESP32-WROOM-32 is a very popular chip used for the internet of things applications. The main part of this module is ESP32-D0WDQ6 chip.
  • It has 48 pins but all pins are not available to use in devkit. You will see more information about it in the later part of this tutorial.
  • It consists of an on-chip WiFi module, Bluetooth low energy module, and Bluetooth module. So if you are working on an embedded systems project, where you need all these modules, you can simply use this board instead of using off the shelf all components one by one. Due to these features, it can be used for many embedded systems applications.
  • It is a very low-cost board and can be purchased around 10-15$.
  • It consists of two cores and each core can be controlled separately.
  • It can operate at the variable frequency range from 80 MHz to 240 MHz.
  • It has a special ultra-low power co-processor. A user can power off processors and can use a low power coprocessor to monitor peripherals at low power like GPIO pins.
  • The diagram below shows the complete diagram of D0WDQ6 chip. ESP32 BLOCK DIAGRAM

you can check these articles on ESP32:

you can check more information about this chip here.

Main features of ESP32

Followings are the main features of ESP32 :

  • It has on board 18 Analog to digital converts ADCs.  Each ADC is 12 bit SAR technology based.
  • 2 digital to analog converts DACs.
  • It integrates 9 touch sensors.
  • For communication, it has 2 UART communications channels, 2 I2C communications interfaces two I2S channels and one CAN communication interface.
  • It has 16 pulse width modulation channels.
  • It also has a cryptographic hardware acceleration module for various cryptographic algorithms like RSA, AES.

Introduction ESP32 pinout

The picture given below explains all the pins of this board. As I mentioned earlier chip which is used with the board has 48 GPIO pins. But we can not use all pins through these development boards.ESP32 pinout mapping

GPIO pins of ESP32 DEVKIT

As mentioned earlier, the chip used with this board has 48 GPIO pins, but all pins are not accessible through development boards. ESP32 devkit has 36 pins and 18 on each side of the board as shown in the picture above. It has 34 GPIO pins and each pin has multiple functionalities which can be configured using specific registers.  There are many types of GPIOs available like digital input, digital output, analog input, and analog output, capacitive touch, UART communication and many other features mentioned above.ESP32 DEVKIT Pin mapping

Digital input GPIO pins

It has six GPIO pins which can be used as digital input pins only. They cannot be configured as digital output pins. They do not have internally connected push pull resistors. They can only be used as digital input pins.

  • GPIO34
  • GPIO35
  • GPIO36
  • GPIO37
  • GPIO38
  • GPIO39

Check this tutorial: How to use push button with ESP32

Analog to digital converter or Analog GPIO pins

This development board supports 18 ADC channels. And each channel is of 12 bits. So it has a good resolution. It can be used to measure analog voltage, current and any analog sensor which provides output in the form of analog voltage. These ADCs can also be used in sleep mode for lower power consumption. Each ADC channel has a resolution of 12 bits which is equal to

     3.3 / 4095 where 3.3 volt is a reference voltage and  4095 is minimum step by ADC

So the minimum voltage, we can measure with these ADC channels is about 80 microvolt. Anything less than this will be an error. I will talk more about it in coming tutorials.  The major drawback of ESP32 ADC is that it has a nonlinear behavior.  you can check the diagram below:

ADC non linear ESP32

Mapping of Analog pins with GPIO pins is shown below:

  • ADC1_CH0 – GPIO36
  • ADC1_CH1 – GPIO37
  • ADC1_CH2 – GPIO38
  • ADC1_CH3 – GPIO39
  • ADC1_CH4 – GPIO32
  • ADC1_CH5-  GPIO33
  • ADC1_CH6 – GPIO34
  • ADC1_CH7 – GPIO35
  • ADC2_CH0 – GPIO4
  • ADC2_CH1 – GPIO0
  • ADC2_CH2 – GPIO2
  • ADC2_CH3 – GPIO15
  • ADC2_CH4 – GPIO13
  • ADC2_CH5 – GPIO12
  • ADC2_CH6 – GPIO14
  • ADC2_CH7 – GPIO27
  • ADC2_CH8 – GPIO25
  • ADC2_CH9 – GPIO26

Check this tutorial : How to use ADC of ESP32 

Digital to analog converter pins

This development board has two onboard integrated 8-bit DAC.  DACs are used to convert digital signals into analog signals. DACs has many applications like voltage control and PWM control.

  • DAC_1 –  GPIO25
  • DAC_2 – GPIO26

Touch sensor pins of Devkit

ESP-WROOM-32 provide on board 10 capacitive touch sensors. So you don’t need to use separate touch sensors in your project when you are using this development board. These capacitive touch sensors can be used to detect any electrical and magnetic waves around like magnetic field detection. You can use a small array of pads instead of push buttons with these touch sensors.

  • TOUCH0 – GPIO4
  • TOUCH1 – GPIO0
  • TOUCH2 – GPIO2
  • TOUCH3 – GPIO15
  • TOUCH4 – GPIO13
  • TOUCH5 – GPIO12
  • TOUCH6 – GPIO14
  • TOUCH7 – GPIO27
  • TOUCH8 – GPIO33
  • TOUCH9 – GPIO32

How to use touch pins and how to use touch pins as a digital button? 

Memory card interfacing pins

It also supports memory card interfacing through these pins.

  • HS2_CLK – MTMS
  • HS2_CMD – MTDO
  • HS2_DATA0 – GPIO2
  • HS2_DATA1 – GPIO4
  • HS2_DATA2 – MTDI
  • HS2_DATA3 – MTCK

External interrupt pins

All general purpose input output pins can be used as external interrupt. External interrupts are very useful. When you want to monitor change across any pin, you can use this pin as an interrupt instead of repeatedly monitoring the state of this pin.

PWM GPIO pins

All general purpose input output pins can be used to generate PWM except digital input pins from GPIO pins 34-39. Because these pins cannot be used as digital output pins. PWM signals are digital output signals. The maximum frequency of these PWM pins is 80 MHz.  you can configure any other pin as a PWM pin by following these steps:

  • Select a frequency for pulse width modulation.
  • Select the duty cycle or pulse width.
  • Select the PWM channel. ESP32 provides 16 PWM channels.
  • Assign a digital pin to select the PWM channel.

Complete step by step guide on ESP32 PWM with examples 

PWM motor control feature

It also supports motor control feature through internal registers of ESP32 chip. you just need to configure these registers with any GPIO pins. you can find more information about these registers in the datasheet. Registers names are given below:

  • PWM1_OUT_IN0~2
  • PWM0_FLT_IN0~2
  • PWM1_FLT_IN0~2
  • PWM0_CAP_IN0~2
  • PWM1_CAP_IN0~2
  • PWM0_SYNC_IN0~2
  • PWM1_SYNC_IN0~2

I2C communication pins

It has dedicated pins available for two-wire I2C communication. One pin is used for data transfer and another pin is used for clock synchronization.

  • GPIO21 is SDA pin.
  • GPIO22 is SCL pin.

We have posted an article on I2C LCD interfacing with ESP32. This post explains how to I2C pins. you can read complete article:

RTC pins of ESP32 devKit

This board also provide RTC pins which can be used to trigger ESP32 from sleep mode.

  • RTC_GPIO0 – GPIO36
  • RTC_GPIO3  -GPIO39
  • RTC_GPIO4 – GPIO34
  • RTC_GPIO5 – GPIO35
  • RTC_GPIO6 – GPIO25
  • RTC_GPIO7 -GPIO26
  • RTC_GPIO8 – GPIO33
  • RTC_GPIO9 – GPIO32
  • RTC_GPIO10 -GPIO4
  • RTC_GPIO11 – GPIO0
  • RTC_GPIO12 – GPIO2
  • RTC_GPIO13 – GPIO15
  • RTC_GPIO14 – GPIO13
  • RTC_GPIO15 – GPIO12
  • RTC_GPIO16 – GPIO14
  • RTC_GPIO17 – GPIO27

Hall sensor pin

It also has one hall sensor which is used to detect the magnetic field. Whenever you please this development board in the magnetic field, ESP32 generates a small voltage which can be measured with any pin. I will post a tutorial on in coming articles.  Other features of ESP32 development board and pins are shown in the above picture.

If you liked this tutorial, you may also like to check these tutorials and projects:

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