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Board overview
SparkFun ESP32 Thing
SparkFun · Thing
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Showing 28 of 28 pins
Simplified technical illustration. Pin data is source-backed; verify against the linked documentation before wiring.
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Mapped source · SparkFun ESP32 Thing hookup guideOfficial- ESP32 (dual-core Xtensa LX6); pin data from the SparkFun ESP32 Thing hookup guide.
- GPIO0 is the BOOT button — must be HIGH (or floating with pullup) for normal boot.
- GPIO12 must be LOW at boot (selects 3.3 V flash voltage); internal pulldown provided.
- GPIO6–GPIO11 are connected to the internal SPI flash and must not be used as general GPIO.
- ADC2 pins (GPIO0, 2, 4, 12–15, 25–27) cannot be used while Wi-Fi is active.
- GPIO34, 35, 36, 39 are input-only (no pull resistors, no output drive).
- GPIO is 3.3 V only.
All 28 pins
| # | Signal | Role | Net | Also / notes |
|---|---|---|---|---|
| 1 | Ground | GND | ||
| 3 | Alt | BOOT button; ADC2_CH1; must be HIGH at reset. | ||
| 5 | GPIO | ADC2_CH0 | ||
| 7 | GPIO | |||
| 9 | SPI | SPI | VSPI CLK | |
| 11 | SPI | SPI | VSPI MISO | |
| 13 | I2C | I2C | I2C SDA | |
| 15 | UART | UART0 | UART0 RX | |
| 17 | UART | UART0 | UART0 TX | |
| 19 | I2C | I2C | I2C SCL | |
| 21 | SPI | SPI | VSPI MOSI | |
| 23 | DAC | DAC1 / ADC2_CH8 | ||
| 25 | DAC | DAC2 / ADC2_CH9 | ||
| 27 | GPIO | ADC2_CH7 | ||
| 2 | Power | 3V3 | ||
| 4 | System | Chip enable (active HIGH). | ||
| 6 | ADC | Input only; ADC1_CH0. | ||
| 8 | ADC | Input only; ADC1_CH3. | ||
| 10 | ADC | Input only; ADC1_CH6. | ||
| 12 | ADC | Input only; ADC1_CH7. | ||
| 14 | ADC | ADC1_CH4 | ||
| 16 | ADC | ADC1_CH5 | ||
| 18 | GPIO | ADC2_CH4 | ||
| 20 | GPIO | ADC2_CH5 · Boot strapping: must be LOW at reset. | ||
| 22 | GPIO | ADC2_CH6 | ||
| 24 | UART | UART2 | UART2 RX / LED pin | |
| 26 | UART | UART2 | UART2 TX | |
| 28 | Ground | GND |