ESP32 DevKit V1 pinout — all 30 pins explained

What every ESP32 DevKit V1 pin can do: GPIO, ADC, input-only, strapping pins, I2C, SPI, UART, and the rules for safe wiring.

Rules you must know

Every GPIO outputs and tolerates at most 3.3 V. A signal from a 5 V device (HC-SR04 Echo) must go through a 1 kΩ + 2 kΩ voltage divider.

No output and no internal pull-up. Ideal for analog reading (potentiometer, LDR), bad for a button without an external resistor.

GPIO 0, 2, 4, 12–15, 25–27 use ADC2. When WiFi is on, analogRead() on them returns garbage. Use ADC1 (32–39).

They set the boot state. Do not attach anything that pulls them HIGH/LOW at power-up, especially GPIO 12.

Recommended ≤ 12 mA, never > 40 mA. LED with 220 Ω = 6 mA, OK. Motor, relay coil, speaker → through a transistor/module.

Defaults, but can be changed with Wire.begin(sda, scl). Several devices on one bus — each with its own address.

The ESP32 has 16 LEDC channels that map to any output pin. ledcAttach(pin, freq, bits) + ledcWrite(pin, val).

If you take them, you lose the Serial Monitor and uploading may fail. For a second serial device use TX2/RX2 (17, 16).

Pin	GPIO	What it is	Where it connects / why
EN	—	Reset (active LOW)	Connect to GND for reset. The EN button does the same. Not a GPIO.
VP	36	ADC1_CH0, Input only	No pull-up/pull-down. Excellent for analog sensors. Noisy when WiFi is on without a capacitor.
VN	39	ADC1_CH3, Input only	No pull-up/pull-down. Reading only.
D34	34	ADC1_CH6, Input only	The most common choice for a potentiometer / LDR. No internal resistors.
D35	35	ADC1_CH7, Input only	Input only, ADC1.
D32	32	ADC1_CH4, TOUCH9, XTAL_32K_P	Full GPIO with ADC1 — good for analog and digital.
D33	33	ADC1_CH5, TOUCH8, XTAL_32K_N	Full GPIO with ADC1.
D25	25	DAC1, ADC2_CH8	True analog output (0–3.3 V, 8-bit). ADC2 does not work with WiFi.
D26	26	DAC2, ADC2_CH9	Second DAC output. ADC2 does not work with WiFi.
D27	27	ADC2_CH7, TOUCH7	Free GPIO, safe for everything.
D14	14	ADC2_CH6, TOUCH6, HSPI_CLK	Outputs a short PWM signal at boot — not for relays.
D12	12	ADC2_CH5, TOUCH5, HSPI_Q	STRAPPING: if HIGH at power-up, the board will not boot! Avoid it or use it only as an output.
D13	13	ADC2_CH4, TOUCH4, HSPI_ID	Free GPIO, good for servo/PWM.
GND	—	Ground	Connect it to the − rail of the breadboard.
VIN	—	5 V input/output	On USB there is ~5 V here for servo, HC-SR04, relay. The ESP32 can also be powered from here (5–12 V) without USB.

Pin	GPIO	What it is	Where it connects / why
D23	23	VSPI_MOSI	SPI data to a device. Free if you do not use SPI.
D22	22	I2C SCL (default)	Clock for OLED and I2C sensors.
TX0	1	UART0 TX	Goes to USB → Serial Monitor. Do not use it for anything else.
RX0	3	UART0 RX	Receives from USB. HIGH at boot. Do not use it for anything else.
D21	21	I2C SDA (default)	Data for OLED and I2C sensors.
D19	19	VSPI_MISO	SPI data from a device. Free if you do not use SPI.
D18	18	VSPI_CLK	SPI clock. Free if you do not use SPI.
D5	5	VSPI_CS, Strapping	Outputs a short PWM signal at boot — do not use it for a relay or motor. Otherwise free (SPI CS, LED, buzzer).
TX2	17	UART2 TX	Free serial port for GPS, Bluetooth module.
RX2	16	UART2 RX	Free serial port.
D4	4	ADC2_CH0, TOUCH0	Free, often used for DHT22. ADC2 does not work with WiFi.
D2	2	Built-in LED, ADC2_CH2, TOUCH2	The blue LED on the board. Strapping — must be LOW/floating during upload, but perfectly fine for an LED.
D15	15	ADC2_CH3, TOUCH3, HSPI_CS	Strapping: if LOW at power-up, no boot messages. Outputs PWM at boot.
GND	—	Ground	Second GND pin — for the other side of the breadboard.
3V3	—	3.3 V output	From the board regulator, ~500 mA total. For 3.3 V sensors.