ESP32 Pin reference

ES​P32 Chip equipped 48 A pin with multiple functions . Not all pins are exposed to all ESP32 In the development board , Some pins cannot be used .

On how to use ESP32 GPIO There are many problems . What should you use pin？ What should be avoided in the project pin？ This article aims to become a for ESP32 Of GPIO Provide a simple and easy to understand Reference Guide .

Be careful ： Not all GPIO Can be accessed in all development boards , But every particular GPIO All work in the same way , No matter what development board you use .

EN Pin , Of the board EN yes 3.3V Enable pin of regulator . It was pulled up , So connect to GND To disable 3.3V Regulator . for example , This means that you can use this pin connected to the button to restart your ESP32.

ESP32 Peripherals

ESP32 Peripherals include ：

18 An analog-to-digital converter （ADC） passageway

3 individual SPI Interface

3 individual UART Interface

2 individual I2C Interface

16 A pulse width modulation output channel

2 A / D converter （DAC）

2 individual I2S Interface

10 A capacitive sensor GPIO

ADC（ A / D converter ） and DAC（ A / D converter ） Functions are assigned to specific static pins . however , You can decide which pins are UART、I2C、SPI、PWM etc. , You just need to allocate them in the code . It's possible , because ESP32 The multiplexing function of the chip .

Each board is slightly different , For example, this one I bought recently is like this , It's also good , Wide voltage power supply, maximum support 18 v , Um. very XX.

Only input pins

GPIO34 To 39 yes GPIs– Only input pins . These pins have no internal pull-up or pull-down resistors . They cannot be used as output , Therefore, these pins can only be used as input ：

GPIO 34

GPIO 35

GPIO 36

GPIO 39

Integrated into the ESP-WROOM-32 Upper SPI Flash memory

GPIO 6 To GPIO 11 In some ESP32 The development board is open . however , These pins are connected to ESP-WROOM-32 Integration on chip SPI Flash memory , Not recommended for other purposes . therefore , Do not use these pins in the project ：

GPIO 6（SCK/CLK）

GPIO 7（SDO/SD0）

GPIO 8（SDI/SD1）

GPIO 9（SHD/SD2）

GPIO 10（SWP/SD3）

GPIO 11（CSC/CMD）

Capacitive touch GPIO

ESP32 Yes 10 An internal capacitive touch sensor . They can sense any change in charged matter , Like human skin . therefore , They can detect when touching with their fingers gpio Changes caused by . These pins can be easily integrated into the capacitor pad , And replace mechanical buttons . Capacitive contacts can also be used to wake up ESP32 Deep sleep .

These internal touch sensors are connected to these sensors GPIO：

T0 (GPIO 4)

T1 (GPIO 0)

T2 (GPIO 2)

T3 (GPIO 15)

T4 (GPIO 13)

T5 (GPIO 12)

T6 (GPIO 14)

T7 (GPIO 27)

T8 (GPIO 33)

T9 (GPIO 32)

A / D converter （ADC）

ESP32 Yes 18 x 12 position ADC Input channel （ and ESP8266 Only 1 x 10 position ADC）. These can be used as ADC And the corresponding channel GPIO：

ADC1_CH0 (GPIO 36)

ADC1_CH1 (GPIO 37)

ADC1_CH2 (GPIO 38)

ADC1_CH3 (GPIO 39)

ADC1_CH4 (GPIO 32)

ADC1_CH5 (GPIO 33)

ADC1_CH6 (GPIO 34)

ADC1_CH7 (GPIO 35)

ADC2_CH0 (GPIO 4)

ADC2_CH1 (GPIO 0)

ADC2_CH2 (GPIO 2)

ADC2_CH3 (GPIO 15)

ADC2_CH4 (GPIO 13)

ADC2_CH5 (GPIO 12)

ADC2_CH6 (GPIO 14)

ADC2_CH7 (GPIO 27)

ADC2_CH8 (GPIO 25)

ADC2_CH9 (GPIO 26)

Be careful ： Use Wi-Fi Can not be used when ADC2 Pin . therefore , If you use Wi-Fi, And can't get from ADC2 GPIO Get value , You can consider using ADC1 GPIO, This should solve your problem .

ADC The input channel has 12 Bit resolution . This means you can get 0 To 4095 Analog reading between , among 0 Corresponding to 0V,4095 Corresponding to 3.3V. You can also set the resolution of the channel and ADC Range .

ESP32 ADC Pins have no linear behavior . You may not be able to distinguish 0 and 0.1V, or 3.2 and 3.3V. In the use of ADC Pin time , You need to keep this in mind .

A / D converter （DAC）

ESP32 There are 2 x 8 position DAC passageway , It is used to convert digital signal into analog voltage signal output . These are DAC passageway ：

DAC1 (GPIO25)

DAC2 (GPIO26)

RTC GPIOs

ESP32 Support RTC GPIO. When ESP32 When in deep sleep , You can use routing to RTC Low power consumption subsystem GPIO. these RTC gpio It can be used in ultra-low power consumption （ULP） The coprocessor runtime will ESP32 Wake up from deep sleep . following GPIO It can be used as an external wake-up source .

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)

Pulse width modulation

ESP32 LED PWM The controller has 16 A separate channel , Generate features that can be configured differently PWM The signal . All pins that can be used as outputs can be used as PWM Pin （GPIOs 34 To 39 Can't produce PWM）.

To set the pulse width modulation signal , These parameters need to be defined in the code ：

signal frequency ;

Duty cycle ;

PWM channel ;

To output a signal GPIO.

I2C

ESP32 There are two I2C passageway , Any pin can be set to SDA or SCL. take ESP32 And Arduino IDE When used together , Default I2C Pin for ：

GPIO 21（SDA）

GPIO 22（SCL）

If you want to use other pins , When using wire Library , Just call ：

Wire.begin(SDA, SCL);

SPI By default ,SPI Of pin It maps to ：

interrupt

all GPIO Can be configured to interrupt .

Strapping pins Note here ： Some of these pins affect startup , It's better not to send a signal when connecting external equipment to start .

ESP32 The chip has the following Strapping pins：

GPIO 0

GPIO 2

GPIO 4

GPIO 5（ Must be high during startup ）

GPIO 12（ Must be low during start-up ）

Please note that ESP32 Of IO12, This IO The level when the port is powered on will determine the external flash（ The one that stores the program ） Working voltage of , When the foot is high when powered on, it is considered flash Work in 1.8V, If it is low, it means flash Work in 3.3V. Commonly used like Wroom-32 This pin of the series module has been pulled down , namely flash Is working in 3.3V Of , If the external circuit is strongly connected and pulled up, the module may work abnormally .

GPIO 15（ Must be high during startup ）

These are used to put ESP32 Put in boot loader or burn mode . In most built-in USB/Serial On the development board of , You don't need to worry about the status of these pins . The circuit board puts the pins in the correct burn or start mode . of ESP32 More information about boot mode selection , See here .

however , If you have peripherals connected to these pins , You may have difficulties , Trying to upload a new code , Burn with new firmware ESP32 Or reset the board . If you have some peripherals connected to Strapping pins, And you are uploading code or burning ESP32 We have problems , It may be that these peripherals prevent ESP32 Enter the correct mode . Please read the guidance mode selection document to guide you in the right direction . Reset 、 After burning or starting , These pins work as expected .

Pins HIGH at Boot

some GPIO Change its state to high or output at startup or reset PWM The signal . It means , If the output is connected to these gpio, It's in ESP32 Unexpected results may be obtained when resetting or booting .

GPIO 1

GPIO 3

GPIO 5

GPIO 6 to GPIO 11 (connected to the ESP32 integrated SPI flash memory – not recommended to use).

GPIO 14

GPIO 15

Enable （EN）

Enable （EN） yes 3.3V Enable pin of regulator . It was pulled up , So grounding makes 3.3V The regulator fails . for example , This means that you can use this pin connected to the button to restart ESP32.

GPIO Current consumption

according to ESP32 In the data sheet “ Recommended operating conditions ” part , Every GPIO The absolute maximum current of is 40 Ma .

ESP32 Built in Hall effect sensor

ESP32 It also has a built-in Hall effect sensor , It can detect the change of surrounding magnetic field .