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ESP32-WROOM
Compact Wi-Fi and Bluetooth module based on the ESP32-D0WDQ6 chip, suitable for integration into various embedded systems.
25.5 × 18 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
32· 16 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
35 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 36 | SENSOR_VPGPIO36 | strapping | adc | ADC1_CH0, RTC_GPIO0 |
| 2 | 39 | SENSOR_VNGPIO39 | strapping | adc | ADC1_CH3, RTC_GPIO3 |
| 3 | 34 | IO34GPIO34 | strapping | adc | ADC1_CH6, RTC_GPIO4 |
| 4 | 35 | IO35GPIO35 | strapping | adc | ADC1_CH7, RTC_GPIO5 |
| 5 | 32 | IO32GPIO32 | safe | adc · touch | XTAL_32K_P (32.768 kHz crystal oscillator input), ADC1_CH4, TOUCH9, RTC_GPIO9 |
| 6 | 33 | IO33GPIO33 | safe | adc · touch | XTAL_32K_N (32.768 kHz crystal oscillator output), ADC1_CH5, TOUCH8, RTC_GPIO8 |
| 7 | 25 | IO25GPIO25 | safe | adc · dac | DAC_1, ADC2_CH8, RTC_GPIO6, EMAC_RXD0 |
| 8 | 26 | IO26GPIO26 | safe | adc · dac | DAC_2, ADC2_CH9, RTC_GPIO7, EMAC_RXD1 |
| 9 | 27 | IO27GPIO27 | safe | adc · touch | ADC2_CH7, TOUCH7, RTC_GPIO17, EMAC_RX_DV |
| 10 | 14 | IO14GPIO14 | strapping | adc · touch · spi | ADC2_CH6, TOUCH6, RTC_GPIO16, MTMS, HSPICLK, HS2_CLK, SD_CLK, EMAC_TXD2 |
| 11 | 12 | IO12GPIO12 | strapping | adc · touch · spi | ADC2_CH5, TOUCH5, RTC_GPIO15, MTDI, HSPIQ, HS2_DATA2, SD_DATA2, EMAC_TXD3 |
| 12 | - | GNDN/A | ground | - | Ground connection |
| 13 | 13 | IO13GPIO13 | strapping | adc · touch · spi | ADC2_CH4, TOUCH4, RTC_GPIO14, MTCK, HSPID, HS2_DATA3, SD_DATA3, EMAC_RX_ER |
| 14 | 9 | SHD/SD2GPIO9 | strapping | spi | SD_DATA2, SPIHD, HS1_DATA2, U1RXD |
| 15 | 10 | SWP/SD3GPIO10 | strapping | spi | SD_DATA3, SPIWP, HS1_DATA3, U1TXD |
| 16 | 11 | SCS/CMDGPIO11 | strapping | spi | SD_CMD, SPICS0, HS1_CMD, U1RTS |
| 17 | 6 | SCK/CLKGPIO6 | strapping | spi | SD_CLK, SPICLK, HS1_CLK, U1CTS |
| 18 | 7 | SDO/SD0GPIO7 | strapping | spi | SD_DATA0, SPIQ, HS1_DATA0, U2RTS |
| 19 | 8 | SDI/SD1GPIO8 | strapping | spi | SD_DATA1, SPID, HS1_DATA1, U2CTS |
| 20 | 15 | IO15GPIO15 | strapping | adc · touch · spi | ADC2_CH3, TOUCH3, MTDO, HSPICS0, RTC_GPIO13, HS2_CMD, SD_CMD, EMAC_RXD3 |
| 21 | 2 | IO2GPIO2 | strapping | adc · touch · spi | ADC2_CH2, TOUCH2, RTC_GPIO12, HSPIWP, HS2_DATA0, SD_DATA0 |
| 22 | 0 | IO0GPIO0 | strapping | adc · touch | ADC2_CH1, TOUCH1, RTC_GPIO11, CLK_OUT1, EMAC_TX_CLK |
| 23 | 4 | IO4GPIO4 | strapping | adc · touch · spi | ADC2_CH0, TOUCH0, RTC_GPIO10, HSPIHD, HS2_DATA1, SD_DATA1, EMAC_TX_ER |
| 24 | 16 | IO16GPIO16 | strapping | - | HS1_DATA4, U2RXD, EMAC_CLK_OUT |
| 25 | 17 | IO17GPIO17 | strapping | - | HS1_DATA5, U2TXD, EMAC_CLK_OUT_180 |
| 26 | 5 | IO5GPIO5 | strapping | spi | VSPICS0, HS1_DATA6, EMAC_RX_CLK |
| 27 | 18 | IO18GPIO18 | safe | spi | VSPICLK, HS1_DATA7 |
| 28 | 19 | IO19GPIO19 | safe | spi | VSPIQ, U0CTS, EMAC_TXD0 |
| 29 | - | NCN/A | safe | - | No connection |
| 30 | 21 | IO21GPIO21 | safe | spi | VSPIHD, EMAC_TX_EN |
| 31 | 3 | RXD0GPIO3 | uart | - | U0RXD, CLK_OUT2 |
| 32 | 1 | TXD0GPIO1 | uart | - | U0TXD, CLK_OUT3, EMAC_RXD2 |
| 33 | 22 | IO22GPIO22 | safe | spi | VSPIWP, U0RTS, EMAC_TXD1 |
| 34 | 23 | IO23GPIO23 | safe | spi | VSPID, HS1_STROBE |
| 35 | - | GNDN/A | ground | - | Ground connection |
Start with these
10 pins with no boot or system involvementIO32GPIO32IO33GPIO33IO25GPIO25IO26GPIO26IO27GPIO27IO18GPIO18IO19GPIO19IO21GPIO21IO22GPIO22IO23GPIO23
Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| SENSOR_VP | GPIO36 (SENSOR_VP) | Cannot be used as output; only suitable for input (e.g., analog read). | Other |
| SENSOR_VN | GPIO39 (SENSOR_VN) | Cannot be used as output; only suitable for input. | Other |
| IO34 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| IO35 | GPIO35 | Cannot be used as output; only suitable for input. | Other |
| IO14 | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| IO12 | MTDI (GPIO12) | Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used. | Strapping |
| IO13 | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| IO15 | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| IO2 | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| IO0 | GPIO0 | Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| IO4 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| IO5 | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| SHD/SD2 | GPIO9 (Flash SD2) | Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO. | Flash |
| SWP/SD3 | GPIO10 (Flash SD3) | Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO. | Flash |
| SCS/CMD | GPIO11 (Flash CMD) | Used by internal flash (chip select/command); not available for general use. | Flash |
| SCK/CLK | GPIO6 (Flash SCK) | Used for internal flash/PSRAM communication; not available for general GPIO. | Flash |
| SDO/SD0 | GPIO7 (Flash SD0) | Used for internal flash/PSRAM data; not available for general GPIO. | Flash |
| SDI/SD1 | GPIO8 (Flash SD1) | Used for internal flash/PSRAM data; not available for general GPIO. | Flash |
| IO16 | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| IO17 | GPIO17 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| RXD0 | U0RXD (GPIO3) | Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads. | USB |
| TXD0 | U0TXD (GPIO1) | Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console. | USB |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The ESP32-WROOM breaks out 35 pins in total: 32 GPIO for your project, with GND handling power. On the analog side there are 16 ADC-capable pins for sensors…
The ESP32-WROOM breaks out 35 pins in total: 32 GPIO for your project, with GND handling power.
On the analog side there are 16 ADC-capable pins for sensors and battery monitoring, 10 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, IO32, IO33, IO25, IO26 and 6 more are free of any such role - the safest first picks. 12 of the exposed pins carry boot-time or system duties on the ESP32 (SENSOR_VP, SENSOR_VN, IO34 and 9 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Serial chip: onboard. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO32 - swap for your board's LED pin if different.
Board: Esp32 Dev
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(32, OUTPUT);
digitalWrite(32, LOW); // on (often inverted)[env:esp32-wroom]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO32
output:
- platform: gpio
pin: 32
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32 · 25.5 × 18 mmCompute
MCU
ESP32
Clock
240 MHz
SRAM · Flash
520 KB · 4MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
4.2 LE
Antenna
PCB
I/O
GPIO · ADC
32 · 16
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
-
Serial
-
Boot address
0x1000
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · DIO
Sketch · Data
1.25 MB · 320 KB
25.5 × 18 mm
The ESP32-WROOM uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with DIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
32 GPIO are broken out - more than most ESP32 boards, so the pin budget is rarely the constraint.
Resources
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