ESP32 GPIO Specifications

Important Considerations:

ESP32 Variants: This table is for the original ESP32 (e.g., ESP32-D0WDQ6). Newer variants (S2, S3, C3, H2) have different capabilities. Always check the specific datasheet.

Module vs. Chip: Modules (WROOM, WROVER) may not expose all pins.

SPI Flash Pins (GPIO 6-11): These are typically connected to the integrated SPI Flash on modules and should generally NOT be used for other purposes.

GPIO Matrix: Most peripherals (UART, SPI, I2C, PWM) can be routed to *almost any* digital I/O pin. This table lists inherent hardware features (ADC, Touch, DAC) and common/default assignments.

ADC2 Limitation: ADC2 channels (*) cannot be used when Wi-Fi is active. Use ADC1 for simultaneous Wi-Fi and ADC readings.

Strapping Pins: Affect boot mode and flash settings. Ensure external circuits don't interfere during boot.

Input Only Pins (GPIO 34-39): Lack internal pull-up/pull-down resistors and cannot be configured as outputs.

RTC GPIOs: Can wake the ESP32 from deep sleep and be controlled by the ULP co-processor.

PWM: Any 'Yes' I/O pin can generally be used for PWM output (via LEDC peripheral).

GPIO	I/O Capable	Int. PU/PD	ADC Ch.	DAC Ch.	Touch Ch.	RTC GPIO	Strapping Pin?	Default/Common Peripherals & Notes
0	Yes	Yes	ADC1_CH1	-	T1	RTC_11	Yes	Boot mode select (0=Download, 1=Flash). Driven Low for Download. Often suggested for I2C SDA.
1	Yes	Yes	-	-	-	-	No	UART0 TXD (Programming/Log). HIGH at boot.
2	Yes	Yes	ADC1_CH2	-	T2	RTC_12	Yes	Must be LOW to enter serial bootloader. Often onboard LED. HSPIWP (WROVER).
3	Yes	Yes	-	-	-	-	No	UART0 RXD (Programming/Log). HIGH at boot.
4	Yes	Yes	ADC1_CH0	-	T0	RTC_10	No	HSPIHD (WROVER).
5	Yes	Yes	-	-	-	-	Yes	VSPICS0. Must be HIGH during boot for SPI flash boot.
6	Yes	Yes	-	-	-	-	No	SPI Flash CLK (SCK/SD_CLK) - DO NOT USE on WROOM/WROVER
7	Yes	Yes	-	-	-	-	No	SPI Flash DATA0 (SD0/SD_DATA0) - DO NOT USE on WROOM/WROVER
8	Yes	Yes	-	-	-	-	No	SPI Flash DATA1 (SD1/SD_DATA1) - DO NOT USE on WROOM/WROVER
9	Yes	Yes	-	-	-	-	No	SPI Flash DATA2 (SD2/SD_DATA2/HSPIHD) - DO NOT USE on WROOM/WROVER
10	Yes	Yes	-	-	-	-	No	SPI Flash DATA3 (SD3/SD_DATA3/HSPIWP) - DO NOT USE on WROOM/WROVER
11	Yes	Yes	-	-	-	-	No	SPI Flash CMD (CMD/SD_CMD) - DO NOT USE on WROOM/WROVER
12	Yes	Yes	ADC2_CH5	-	T5	RTC_15	Yes	JTAG TDO / MTDI. Default HSPIQ (MISO). Pulled LOW by default; HIGH at boot affects flash voltage.
13	Yes	Yes	ADC2_CH4	-	T4	RTC_14	No	JTAG TCK / MTCK. Default HSPICLK.
14	Yes	Yes	ADC2_CH6	-	T6	RTC_16	No	JTAG TMS / MTMS. Default HSPID (MOSI).
15	Yes	Yes	ADC2_CH3	-	T3	RTC_13	Yes	JTAG TDI / MTDO. Default HSPICS0. Must be LOW during boot (unless silencing boot messages).
16	Yes	Yes	-	-	-	-	No	UART2 RXD. Used for PSRAM on WROVER - Avoid if using PSRAM.
17	Yes	Yes	-	-	-	-	No	UART2 TXD. Used for PSRAM on WROVER - Avoid if using PSRAM.
18	Yes	Yes	-	-	-	-	No	VSPICLK (SPI Clock)
19	Yes	Yes	-	-	-	-	No	VSPIQ (SPI MISO)
21	Yes	Yes	-	-	-	-	No	Common I2C SDA
22	Yes	Yes	-	-	-	-	No	Common I2C SCL
23	Yes	Yes	-	-	-	-	No	VSPID (SPI MOSI)
25	Yes	Yes	ADC2_CH8	DAC_1	T8	RTC_6	No	DAC Output 1
26	Yes	Yes	ADC2_CH9	DAC_2	T9	RTC_7	No	DAC Output 2
27	Yes	Yes	ADC2_CH7	-	T7	RTC_17	No	-
32	Yes	Yes	ADC1_CH4	-	T9	RTC_9	No	32kHz Crystal Input (XTAL_32K_P)
33	Yes	Yes	ADC1_CH5	-	T8	RTC_8	No	32kHz Crystal Output (XTAL_32K_N)
34	Input Only	No	ADC1_CH6	-	-	RTC_4	No	Input Only! No internal pull-up/down.
35	Input Only	No	ADC1_CH7	-	-	RTC_5	No	Input Only! No internal pull-up/down.
36	Input Only	No	ADC1_CH0	-	-	RTC_0	No	SENSOR_VP. Input Only! No internal pull-up/down.
37	Input Only	No	ADC1_CH1	-	-	RTC_1	No	SENSOR_CAPP. Input Only! No internal pull-up/down. (Often not exposed)
38	Input Only	No	ADC1_CH2	-	-	RTC_2	No	SENSOR_CAPN. Input Only! No internal pull-up/down. (Often not exposed)
39	Input Only	No	ADC1_CH3	-	-	RTC_3	No	SENSOR_VN. Input Only! No internal pull-up/down.

GPIO

I/O Capable

Int. PU/PD

ADC Ch.

DAC Ch.

Touch Ch.

RTC GPIO

Strapping Pin?

Default/Common Peripherals & Notes

Yes

ADC1_CH1

RTC_11

Yes

Boot mode select (0=Download, 1=Flash). Driven Low for Download. Often suggested for I2C SDA.

Yes

UART0 TXD (Programming/Log). HIGH at boot.

Yes

ADC1_CH2

RTC_12

Yes

Must be LOW to enter serial bootloader. Often onboard LED. HSPIWP (WROVER).

Yes

UART0 RXD (Programming/Log). HIGH at boot.

Yes

ADC1_CH0

RTC_10

HSPIHD (WROVER).

Yes

VSPICS0. Must be HIGH during boot for SPI flash boot.

Yes

SPI Flash CLK (SCK/SD_CLK) - DO NOT USE on WROOM/WROVER

Yes

SPI Flash DATA0 (SD0/SD_DATA0) - DO NOT USE on WROOM/WROVER

Yes

SPI Flash DATA1 (SD1/SD_DATA1) - DO NOT USE on WROOM/WROVER

Yes

SPI Flash DATA2 (SD2/SD_DATA2/HSPIHD) - DO NOT USE on WROOM/WROVER

Yes

SPI Flash DATA3 (SD3/SD_DATA3/HSPIWP) - DO NOT USE on WROOM/WROVER

Yes

SPI Flash CMD (CMD/SD_CMD) - DO NOT USE on WROOM/WROVER

Yes

ADC2_CH5

RTC_15

Yes

JTAG TDO / MTDI. Default HSPIQ (MISO). Pulled LOW by default; HIGH at boot affects flash voltage.

Yes

ADC2_CH4

RTC_14

JTAG TCK / MTCK. Default HSPICLK.

Yes

ADC2_CH6

RTC_16

JTAG TMS / MTMS. Default HSPID (MOSI).

Yes

ADC2_CH3

RTC_13

Yes

JTAG TDI / MTDO. Default HSPICS0. Must be LOW during boot (unless silencing boot messages).

Yes

UART2 RXD. Used for PSRAM on WROVER - Avoid if using PSRAM.

Yes

UART2 TXD. Used for PSRAM on WROVER - Avoid if using PSRAM.

Yes

VSPICLK (SPI Clock)

Yes

VSPIQ (SPI MISO)

Yes

Common I2C SDA

Yes

Common I2C SCL

Yes

VSPID (SPI MOSI)

Yes

ADC2_CH8

DAC_1

RTC_6

DAC Output 1

Yes

ADC2_CH9

DAC_2

RTC_7

DAC Output 2

Yes

ADC2_CH7

RTC_17

Yes

ADC1_CH4

RTC_9

32kHz Crystal Input (XTAL_32K_P)

Yes

ADC1_CH5

RTC_8

32kHz Crystal Output (XTAL_32K_N)

Input Only

ADC1_CH6

RTC_4

Input Only! No internal pull-up/down.

Input Only

ADC1_CH7

RTC_5

Input Only! No internal pull-up/down.

Input Only

ADC1_CH0

RTC_0

SENSOR_VP. Input Only! No internal pull-up/down.

Input Only

ADC1_CH1

RTC_1

SENSOR_CAPP. Input Only! No internal pull-up/down. (Often not exposed)

Input Only

ADC1_CH2

RTC_2

SENSOR_CAPN. Input Only! No internal pull-up/down. (Often not exposed)

Input Only

ADC1_CH3

RTC_3

SENSOR_VN. Input Only! No internal pull-up/down.

Legend:

Capability Present (Yes / Configurable) Input Only Pin Strapping Pin SPI Flash Pin (Avoid on Modules) ADC Capable Cell *ADC2 requires Wi-Fi off DAC Capable Cell Touch Sensor Capable Cell RTC GPIO Capable Cell - / No: Capability Not Present

ESP32 (Classic) GPIO Hardware Specifications

Important Considerations:

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