ESP32-S3-DevKitC-1 pinout: which pins to use first

The ESP32-S3-DevKitC-1 has 44 pins, and 26 of them are general-purpose pins (GPIO) you can use right away for an LED, a button or a sensor. Another 7 work fine once you know their one catch. Three are taken by the board's own memory, so skip them.

This is the board in the Schematik Starter Kit, the ESP32-S3-DevKitC-1 N8R8: 8 MB of flash for your program and 8 MB of PSRAM, extra memory for things like screen images.

Want it next to your breadboard? Open the full-size pinout PNG and print it.

Do not connect 5V to a GPIO pin. Every GPIO on the ESP32-S3 expects at most 3.3V plus 0.3V. A 5V sensor output can damage the pin, so check what voltage a part sends back before you wire it.

Our picks for a first build

These are the pins the room monitor in the kit's example projects uses. Each one is a plain GPIO with no catch, so they're a good default for any first build.

Job	Pin	Why this one
I2C SDA (screen data)	GPIO8	Arduino's default SDA on the ESP32-S3
I2C SCL (screen clock)	GPIO9	Arduino's default SCL on the ESP32-S3
Temperature sensor (DHT11)	GPIO4	First GPIO on the left header
Motion sensor (PIR)	GPIO5	Plain input
Light sensor	GPIO6	Plain input
Pushbutton	GPIO7	Plain input
LEDs	GPIO15, GPIO16, GPIO17	Three in a row, each through a 220 Ω resistor

All of them sit on the left header, so one side of the breadboard holds the whole build.

Which pins are I2C on the ESP32-S3?

Almost any free GPIO can be I2C on the ESP32-S3. The chip routes its I2C signals through a switchboard inside, so you pick the two pins in your code. SDA carries the data and SCL is the clock that keeps the board and the screen in step.

We use GPIO8 for SDA and GPIO9 for SCL. They're also the default I2C pins in Espressif's Arduino setup for this chip. On an original ESP32 the default is GPIO21 and GPIO22, which is why older tutorials show different numbers.

What the BOOT button does

The BOOT button connects GPIO0 to GND (ground) while you hold it. The board checks GPIO0 at the moment it starts up:

GPIO0 when the board starts	What happens
High (BOOT not pressed)	Runs the program already on the board
Low (BOOT held down)	Waits for a new program over USB

To put the board into download mode by hand, hold BOOT, press and release RESET, then let go of BOOT. You'll need this when the computer can't upload a new program on its own, for example when the program on the board crashes straight after it starts.

Most of the time you won't touch it. The board has two USB-C ports, and behind the one labeled FLASHING, two small transistors let the computer press BOOT and RESET for you. When you press Deploy in Schematik, the board switches to download mode on its own.

The RESET button restarts the ESP32-S3. It pulls the RST pin (also called EN) low, and your program starts again from the top.

Pins with one catch

These all work as GPIO. Each one has a job at startup or on the board that you need to know about first.

Pin	The catch
GPIO0	The BOOT button. If something holds it low when the board starts, the board waits for a new program instead of running yours.
GPIO46	A strapping pin. Held high at startup together with BOOT, the board can't enter download mode.
GPIO43 (TX), GPIO44 (RX)	Wired to the FLASHING port's USB chip. They carry the Serial Monitor text, so using them for parts can garble uploads and messages.
GPIO19, GPIO20	USB D− and D+ for the port labeled USB. Using them for parts turns that port off.
GPIO38	Shares its line with the RGB LED on the board, so a part here and the LED are wired together.

A strapping pin is a pin the chip reads once, at startup, to decide how to start. After that it's a normal GPIO. The catch only bites when a part holds the pin high or low while the board turns on. GPIO3 and GPIO45 are strapping pins too, but on this board the chip's factory settings ignore them, so they're plain GPIO.

Espressif's first version of this board (v1.0) drives the RGB LED from GPIO48, and Arduino's RGB_BUILTIN still points there. On the kit board, GPIO48 goes only to the header, so use GPIO38 for the LED.

The three pins to skip

GPIO35, GPIO36 and GPIO37 reach the header, but on the N8R8 board they're wired inside the module to the 8 MB of PSRAM. Using them can crash your program, so leave them empty.

GPIO22 to GPIO34 aren't on the headers at all. GPIO22 to GPIO25 don't exist on the ESP32-S3, and the rest connect to the flash and PSRAM inside the module.

Analog pins and Wi-Fi

To read a sensor that outputs a voltage, like a potentiometer, use GPIO1 to GPIO10. These are on ADC1, the first of the chip's two analog-to-digital converters (ADC), which turn a voltage into a number.

GPIO11 to GPIO20 are on ADC2, which shares hardware with Wi-Fi. While Wi-Fi is on, an analog reading on those pins can fail, so keep sensors on ADC1. Digital parts like buttons and LEDs work on them either way.

Full ESP32-S3-DevKitC-1 pin table

Pin numbers count from the end with the module. The left header is J1 and the right header is J3, the names used in the board's schematic.

Left header (J1)

No.	Label	Pin	Use it?	Notes
1	3V3	3.3V	Power	3.3V out for sensors
2	3V3	3.3V	Power	3.3V out for sensors
3	RST	EN	Reset	RESET button pulls it low
4	4	GPIO4	Yes	ADC1, room monitor DHT11
5	5	GPIO5	Yes	ADC1, room monitor PIR
6	6	GPIO6	Yes	ADC1, room monitor light sensor
7	7	GPIO7	Yes	ADC1, room monitor button
8	15	GPIO15	Yes	ADC2, room monitor green LED
9	16	GPIO16	Yes	ADC2, room monitor yellow LED
10	17	GPIO17	Yes	ADC2, room monitor red LED
11	18	GPIO18	Yes	ADC2
12	8	GPIO8	Yes	ADC1, I2C SDA
13	3	GPIO3	Yes	ADC1, strapping pin, ignored on this board
14	46	GPIO46	One catch	Strapping pin
15	9	GPIO9	Yes	ADC1, I2C SCL
16	10	GPIO10	Yes	ADC1
17	11	GPIO11	Yes	ADC2
18	12	GPIO12	Yes	ADC2
19	13	GPIO13	Yes	ADC2
20	14	GPIO14	Yes	ADC2
21	5V	5V	Power	5V from USB
22	GND	GND	Ground

Right header (J3)

No.	Label	Pin	Use it?	Notes
1	G	GND	Ground
2	TX	GPIO43	One catch	Serial Monitor TX
3	RX	GPIO44	One catch	Serial Monitor RX
4	1	GPIO1	Yes	ADC1
5	2	GPIO2	Yes	ADC1
6	42	GPIO42	Yes
7	41	GPIO41	Yes
8	40	GPIO40	Yes
9	39	GPIO39	Yes
10	38	GPIO38	One catch	RGB LED
11	37	GPIO37	Skip	Used by PSRAM
12	36	GPIO36	Skip	Used by PSRAM
13	35	GPIO35	Skip	Used by PSRAM
14	0	GPIO0	One catch	BOOT button
15	45	GPIO45	Yes	Strapping pin, ignored on this board
16	48	GPIO48	Yes
17	47	GPIO47	Yes
18	21	GPIO21	Yes
19	20	GPIO20	One catch	USB D+
20	19	GPIO19	One catch	USB D−
21	GND	GND	Ground
22	GND	GND	Ground

Try it on your desk

Wire a 0.96" SSD1306 OLED screen to 3V3, GND, GPIO8 and GPIO9, and you have the start of the tiny OLED desk command center. Add a DHT11 on GPIO4 and the screen can show your room's temperature too. For how breadboard rows and power rails work, the beginner ESP32 hardware guide walks through it. Which pin would you pick for a buzzer?