REFERENCE · GPIO PINOUT

ESP32 DEVKIT V1 — GPIO Reference

A lookup table for the 30‑pin ESP‑WROOM‑32 board: pick a pin without breaking booting or Wi‑Fi.

Rule of thumb: for a plain input or output, reach for a ✅ safe pin first — GPIO 4, 13, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 32, 33.

1 · Quick categories

Category	Pins	Why
SAFE general‑purpose	4, 13, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 32, 33	Use these first for I/O
STRAPPING (read at boot)	0, 2, 5, 12, 15	Usable, but a wrong level can block uploading
BOOT HIGH/PWM	1, 3, 5, 14, 15	May glitch attached outputs at reset
INPUT‑ONLY	34, 35, 36 (VP), 39 (VN)	No output, no internal pull
DO NOT USE (flash)	6, 7, 8, 9, 10, 11	Wired to the SPI flash — not broken out
🔌 USB serial	1 (TX0), 3 (RX0)	Used by the Serial Monitor — avoid for I/O

I = input · O = output · ADC = analog‑in · Touch = capacitive touch · DAC = analog‑out.

GPIO	Label	I	O	ADC	Touch	Other	Notes
36	VP	✅	—	ADC1_CH0	—	Sensor VP	input only
39	VN	✅	—	ADC1_CH3	—	Sensor VN	input only
34	D34	✅	—	ADC1_CH6	—	—	input only
35	D35	✅	—	ADC1_CH7	—	—	input only
32	D32	✅	✅	ADC1_CH4	T9	—	safe
33	D33	✅	✅	ADC1_CH5	T8	—	safe
25	D25	✅	✅	ADC2_CH8	—	DAC1	safe
26	D26	✅	✅	ADC2_CH9	—	DAC2	safe
27	D27	✅	✅	ADC2_CH7	T7	—	safe
14	D14	✅	✅	ADC2_CH6	T6	HSPI CLK	PWM at boot
12	D12	✅	✅	ADC2_CH5	T5	HSPI MISO	strapping boot fails if pulled HIGH
13	D13	✅	✅	ADC2_CH4	T4	HSPI MOSI	safe
23	D23	✅	✅	—	—	VSPI MOSI	safe
22	D22	✅	✅	—	—	I²C SCL	safe
21	D21	✅	✅	—	—	I²C SDA	safe
19	D19	✅	✅	—	—	VSPI MISO	safe
18	D18	✅	✅	—	—	VSPI CLK	safe
5	D5	✅	✅	—	—	VSPI CS	strapping HIGH at boot; PWM at boot
17	TX2	✅	✅	—	—	UART2 TX	safe
16	RX2	✅	✅	—	—	UART2 RX	safe
4	D4	✅	✅	ADC2_CH0	T0	—	safe
2	D2	✅	✅	ADC2_CH2	T2	On‑board LED	strapping floating/LOW to flash
15	D15	✅	✅	ADC2_CH3	T3	HSPI CS	strapping HIGH at boot; PWM at boot
1	TX0	—	✅	—	—	UART0 TX	Debug output at boot — avoid
3	RX0	✅	—	—	—	UART0 RX	HIGH at boot — avoid
0	(BOOT)	✅	✅	ADC2_CH1	T1	Boot select	strapping tied to BOOT; not on header

Pins 6–11 connect to the module's SPI flash and are not exposed — never use them.

Bus	Signal → pin
I²C	SDA = GPIO 21, SCL = GPIO 22 (reassignable in code)
SPI — VSPI	MOSI 23 · MISO 19 · CLK 18 · CS 5
SPI — HSPI	MOSI 13 · MISO 12 · CLK 14 · CS 15
UART0 (USB Serial)	TX 1 · RX 3
UART2	TX 17 · RX 16
DAC (analog out)	DAC1 = 25 · DAC2 = 26

ADC is 12‑bit → readings 0–4095 for 0–3.3 V.

ADC1 (always usable): GPIO 32, 33, 34, 35, 36, 39
ADC2 (⚠️ unusable while Wi‑Fi is on): GPIO 0, 2, 4, 12, 13, 14, 15, 25, 26, 27

Touch T0–T9: T0=4, T1=0, T2=2, T3=15, T4=13, T5=12, T6=14, T7=27, T8=33, T9=32.

≤ 40 mA per GPIO absolute; keep ≤ ~12 mA in practice.
Logic is 3.3 V — never apply 5 V to a GPIO.
Input‑only pins (34/35/36/39) have no internal pull — add an external resistor for buttons.