ESP32 Gold Edition pinout

InteractiveOpen the ESP32 in 3DTurn the real board over and click any of its 38 holes. Every pad is placed from this design’s own net list.Open in 3D →

Reading this board

Two 19-pin headers, 38 holes: 26 GPIO, six power, and six pads in no net at all. The rows are 25.4 mm apart on a 2.54 mm pitch — ten breadboard columns, so a build has one spare column either side of the board. The module is an ESP32-WROOM-32E, with 4, 8 or 16 MB of flash depending on the variant and no PSRAM on any of them.

Every pin below is read from this design's own net list, so the hole in the table is the hole on your desk. Open the board in 3D to turn it over and click one.

Fifteen of the 26 GPIO have nothing attached and nothing sampled at reset. Six more can be trusted with an analog input on a connected board. The rest are the next two sections.

The six pads that go nowhere

The holes silkscreened 6, 7, 8, 9, 10 and 11 are in no net. On almost every other classic-ESP32 board those six positions carry the module's flash bus, and driving one stops the chip dead. Here they are drilled, plated and labelled for pin-compatibility and then routed nowhere — so unlike most boards, you cannot crash this one by touching them. You also cannot use them. There is no copper on the other side of the pad.

Note what that does not mean. The flash inside the module still runs on the chip's GPIO6 to GPIO11; those lines simply never reach a header. Software that addresses those GPIO numbers is still talking to the flash bus, and still crashes — Serial1 is the one people hit. UART1's dedicated pins are GPIO9 and GPIO10, and the older 2.x Arduino core used them as the default; core 3.x defaults Serial1 to GPIO26 and GPIO27.

When it will not boot

GPIO0, 2, 5, 12 and 15 are sampled as the chip leaves reset, to pick boot mode, flash voltage and SDIO timing. Afterwards they are yours — but a board that flashes over USB and then will not start on its own supply is almost always one of those five. GPIO12 is the usual culprit: pulled high it selects the wrong flash voltage and the chip never gets as far as your code. Boot it bare, then add one wire at a time.

Three of the five — GPIO0, 5 and 15 — also emit a PWM burst while the chip starts. An LED on one flickers at power-up, and a servo or a MOSFET gate sees a few milliseconds of noise before setup() runs.

The RGB LED on GPIO2 is a worked example of getting this right by accident. It is a WS2812, and a WS2812 data line idles low — which is the level the strap wants, so the LED being there costs nothing. Wire something to GPIO2 that idles high and flashing stops working.

Input only, and it is not the ADC that suffers

GPIO34, 35, 36 and 39 have no output driver, no PWM, and no internal pull-up or pull-down. The last one is what bites: a button on one of these needs a real resistor, because INPUT_PULLUP has nothing to switch on.

They are also the best analog inputs the board has — see below — and that is not a coincidence worth working around. Reading a voltage never needed an output driver.

Power

5V is USB bus voltage, and it arrives through a Schottky diode. That matters in both directions: you can feed the board from this pin without pushing current back out into a plugged-in computer, and the pin sits a little below what the cable actually delivers.

3V3 is the output of an AMS1117-3.3, and the module, the bridge and both LEDs already draw from it. Budget about 500 mA for your own parts, less once the radio is transmitting — the regulator is the ceiling, not what the USB cable could deliver.

EN is the chip-enable line, pulled up, with a capacitor that holds the chip in reset for a moment after power arrives so it does not start running while the 3.3 V rail is still on its way up. Tie it to ground through a button and you have a second reset button; the one on the board does exactly that.

All three GND holes are the same net.

Buses

Nothing is fixed on this chip, but these are the defaults the Arduino core assumes and the ones the examples on this site use:

Bus	Pins	Note
I²C	SDA GPIO21, SCL GPIO22	Remappable; 4.7 kΩ pull-ups needed if the module has none
SPI (VSPI)	MOSI GPIO23, MISO GPIO19, SCK GPIO18, SS GPIO5	`SS` lands on a strapping pin — see below
UART0	TX GPIO1, RX GPIO3	The USB serial console — leave it alone
UART2	TX GPIO17, RX GPIO16	`Serial2`'s dedicated pins, and yours; core 3.x defaults `Serial2` to RX 4, TX 25, so pass them to `begin()`

Serial1 is missing from that table on purpose. Its dedicated pins are the flash bus, as above; pass your own pins to Serial1.begin().

The chip-select landing on GPIO5 is the one worth designing around. A chip-select that twitches while the chip boots can make an SPI peripheral see a transaction nobody sent. If a display or an SD card is unreliable only on the first power-up after the supply comes on, move SS to an ordinary pin and set it high yourself before the first transfer.

ADC and DAC

The classic ESP32 has two ADCs and they are not interchangeable.

ADC1 works whatever the radio is doing. Eight channels on the die, six of them on this header: GPIO32, 33, 34, 35, 36 and 39. The other two are GPIO37 and GPIO38, which the WROOM module does not bring out at all.

ADC2 stops working the moment Wi-Fi starts. The driver hands the block to the radio front end, and from then on a read returns an error rather than a wrong number. That is GPIO0, 2, 4, 12, 13, 14, 15, 25, 26 and 27 — ten pins, every one of them still fine as digital I/O. An analog reading that goes dead exactly when you call WiFi.begin() is this, and the fix is to move the input to an ADC1 pin.

So the analog inputs you can trust on a connected board are the six ADC1 pins, and four of the six are the input-only pins from earlier. That is less awkward than it sounds: reading a voltage never needed an output driver.

GPIO25 and GPIO26 are real analog outputs — DAC1 and DAC2, eight bits each. This is the one thing the classic chip does that the S3 dropped completely: an actual voltage, not a filtered PWM. Both are ADC2 channels as well, which is a limit on reading them, not on driving them.

Capacitive touch is T0 to T9, on GPIO0, 2, 4, 12, 13, 14, 15, 27, 32 and 33.

Pins to leave alone

GPIO36 — Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO39 — Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO34 — Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO35 — Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO25 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO26 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO27 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO14 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO12 — Strapping pin. Sets the flash voltage. Boot fails if it is pulled high.
GPIO13 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
9 — L16. Where a devkit would put the flash bus SHD / SD2. This board routes it nowhere — the net list has no net for this pad.
10 — L17. Where a devkit would put the flash bus SWP / SD3. This board routes it nowhere — the net list has no net for this pad.
11 — L18. Where a devkit would put the flash bus CSC / CMD. This board routes it nowhere — the net list has no net for this pad.
GPIO1 — UART0 TX, wired to the USB-UART bridge behind the USB-C port. The chip also prints its boot log here.
GPIO3 — UART0 RX, wired to the USB-UART bridge behind the USB-C port.
GPIO5 — Strapping pin. Sets the SDIO timing. Outputs a PWM signal at boot.
GPIO4 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO0 — BOOT button, with a 10 kΩ pull-up. Held low at reset it drops the chip into the ROM bootloader.
GPIO2 — WS2812B RGB LED, single-wire at 800 kHz. The silkscreen says RGB IO2. Note that GPIO2 is also a strapping pin, so whatever you drive on it must be low or floating while the chip comes out of reset — a WS2812 data line idles low, which is why it works here.
GPIO15 — Strapping pin. Silences the boot log when pulled low. Outputs a PWM signal at boot.
8 — R17. Where a devkit would put the flash bus SDI / SD1. This board routes it nowhere — the net list has no net for this pad.
7 — R18. Where a devkit would put the flash bus SDO / SD0. This board routes it nowhere — the net list has no net for this pad.
6 — R19. Where a devkit would put the flash bus SCK / CLK. This board routes it nowhere — the net list has no net for this pad.

Every pin

Pin	Name	Functions	Notes
3V	3.3 V rail	power	L1. Output of the on-board regulator. Everything on the board runs from it, so budget what the regulator can spare, not what USB can deliver. A steady 3.3 V supply can also power the board through it, but never with USB plugged in at the same time.
EN	EN / reset	power	L2. The regulator enable line, pulled up. Tie it to ground through a button and you have a reset button.
GPIO36	GPIO36	gpio, adc1, input-only	Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO39	GPIO39	gpio, adc1, input-only	Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO34	GPIO34	gpio, adc1, input-only	Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO35	GPIO35	gpio, adc1, input-only	Input only. No output driver, no PWM and no internal pull-up or pull-down, so a button on this pin needs a resistor of its own.
GPIO32	GPIO32	gpio, adc1, touch	L7
GPIO33	GPIO33	gpio, adc1, touch	L8
GPIO25	GPIO25	gpio, adc2, dac	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO26	GPIO26	gpio, adc2, dac	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO27	GPIO27	gpio, adc2, touch	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO14	GPIO14	gpio, adc2, touch	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO12	GPIO12	gpio, adc2, touch	Strapping pin. Sets the flash voltage. Boot fails if it is pulled high.
GND	Ground	power	L14. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GPIO13	GPIO13	gpio, adc2, touch	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
9	Not connected	—	L16. Where a devkit would put the flash bus SHD / SD2. This board routes it nowhere — the net list has no net for this pad.
10	Not connected	—	L17. Where a devkit would put the flash bus SWP / SD3. This board routes it nowhere — the net list has no net for this pad.
11	Not connected	—	L18. Where a devkit would put the flash bus CSC / CMD. This board routes it nowhere — the net list has no net for this pad.
5V	5 V rail	power	L19. The USB rail, upstream of the regulator. Feed the board here if you are not using USB, or take 5 V out if you are.
GND	Ground	power	R1. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GPIO23	GPIO23	gpio, spi	R2. Arduino default: SPI (VSPI) MOSI.
GPIO22	GPIO22	gpio, i2c	R3. Arduino default: Wire (I²C) SCL.
GPIO1	TX	gpio, uart	UART0 TX, wired to the USB-UART bridge behind the USB-C port. The chip also prints its boot log here.
GPIO3	RX	gpio, uart	UART0 RX, wired to the USB-UART bridge behind the USB-C port.
GPIO21	GPIO21	gpio, i2c	R6. Arduino default: Wire (I²C) SDA.
GND	Ground	power	R7. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GPIO19	GPIO19	gpio, spi	R8. Arduino default: SPI (VSPI) MISO.
GPIO18	GPIO18	gpio, spi	R9. Arduino default: SPI (VSPI) SCK.
GPIO5	GPIO5	gpio, spi	Strapping pin. Sets the SDIO timing. Outputs a PWM signal at boot.
GPIO17	GPIO17	gpio, uart	R11. Arduino default: Serial2 TX.
GPIO16	GPIO16	gpio, uart	R12. Arduino default: Serial2 RX.
GPIO4	GPIO4	gpio, adc2, touch	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO0	GPIO0	gpio, adc2, touch	BOOT button, with a 10 kΩ pull-up. Held low at reset it drops the chip into the ROM bootloader.
GPIO2	GPIO2	gpio, adc2, touch	WS2812B RGB LED, single-wire at 800 kHz. The silkscreen says RGB IO2. Note that GPIO2 is also a strapping pin, so whatever you drive on it must be low or floating while the chip comes out of reset — a WS2812 data line idles low, which is why it works here.
GPIO15	GPIO15	gpio, adc2, touch	Strapping pin. Silences the boot log when pulled low. Outputs a PWM signal at boot.
8	Not connected	—	R17. Where a devkit would put the flash bus SDI / SD1. This board routes it nowhere — the net list has no net for this pad.
7	Not connected	—	R18. Where a devkit would put the flash bus SDO / SD0. This board routes it nowhere — the net list has no net for this pad.
6	Not connected	—	R19. Where a devkit would put the flash bus SCK / CLK. This board routes it nowhere — the net list has no net for this pad.

For this board

Electronics Starter Kit: Breadboard, Power Module and Loose Parts — A boxed set of the parts most breadboard circuits start with: an 830-point breadboard, a USB-C power module switchable between 3.3 V and 5 V, jumper wires, resistors, capacitors, LEDs, buttons, potentiometers, diodes, transistors, MOSFETs and two sensors. How to read the parts, set up the bench, and build the first circuits.
Door Sensor — A TinkerBlock board that takes the two bare wires of a magnetic door or window sensor on a screw terminal and puts it between VCC and SIGNAL. A closed sensor reads HIGH; open, SIGNAL floats, because the board has no pull-down, so you set one in setup(). The red LED lights while the sensor is closed: it is not a power light.
3-Axis Accelerometer — A Silan SC7A20H accelerometer on a TinkerBlock board: tilt, orientation, shakes and drops over two shared I²C wires, at address 0x19, with the pull-ups fitted. 3.3 V only.
PCA9685 16-Channel Servo Driver: Sixteen Servos on Two I²C Wires — A PCA9685 board that keeps sixteen servo pulses running by itself while the microcontroller talks to it over I²C. Servo power on V+ from USB-C or a screw terminal, the chip on VCC, six address pads, and a header on each edge so boards plug into each other. Three boards a box, headers soldered.
Breadboard Power Adapters: Standard 5 V / 3.3 V, Step-Down and Booster — Three USB-C breadboard power adapters that plug into both pairs of rails at one end: a standard board with a 5 V / 3.3 V switch per side, a step-down that sets 1.25 to about 3.5 V, and a booster that sets about 4.3 up to 28 V. Which way round they go, why 5 V reads 4.7, and the half-amp fuse that limits all three.
CAN Bus — An SN65HVD230 CAN transceiver on a TinkerBlock board, for 3.3 V microcontrollers with a CAN controller of their own, such as most ESP32 chips. CTX and CRX go straight across, the 120 Ω fitted on every board belongs only on the two end boards, GND runs with a twisted pair, and one board alone can never finish a message.
RS485 Transceiver Boards: MAX485 for 5 V and MAX3485 for 3.3 V — Two RS485 boards from one 12-pack: a MAX485 board for 5 V microcontrollers and a MAX3485 board for 3.3 V ones. The six pins, which board goes with your microcontroller, the 120 Ω fitted on every board that only the two end boards should keep, and RE joined to DE so one pin sets the direction.
Slim Joystick — A thumb stick and six buttons on one long TinkerBlock board, on six pins. X and Y are two potentiometers, read on analog pins; KEY is the click under the stick, LOW at rest and HIGH when pushed; and all six buttons share BTNS, one analog pin, through a ladder of 10 kΩ resistors that gives each its own voltage. One button reads at a time.

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