ESP32-C3 SuperMini Pinout (16-pin)
The $2 RISC-V board that took over every small build. A deep link for every pin, the ADC and PWM flags, and the three strapping warnings that explain nine in ten "my board won't boot" posts.
Safe pinsStrapping warningsPin referenceFAQ
The three rules for the C3 SuperMini.
1. GPIO 2, 8, 9 are strapping pins (GPIO 9 is the BOOT button). External pulls on these can change the boot mode or block flashing.
2. GPIO 11–21 are the flash/PSRAM bus on modules. Never wire them; the board will not boot or will corrupt.
3. 3.3V logic only. The C3 is not 5V-tolerant, so level-shift 5V sensors before connecting.
Safe everyday pins: GPIO 0, 1, 3, 4, 5, 6, 7, 10.
ADC1 is on GPIO 0–4. The C3 has no ADC2, so there is no WiFi conflict: analog reads just work.
Pin reference
5VLeftPower
5V pin (from USB). Powers the on-board regulator; don't feed 5V into GPIOs.
GNDLeftPower
Ground.
3V3LeftPower
3.3V regulated output. Power small sensors only (the regulator is tiny on this board).
GPIO4LeftADCPWM
ADC1_CH4. Safe. Good default for I²C SCL or a servo.
GPIO3LeftADCPWM
ADC1_CH3. Safe.
GPIO2LeftADCPWMStrapping
⚠ ADC1_CH2 and strapping: must be LOW at reset. The on-board RGB LED often sits here.
GPIO1LeftADCPWM
ADC1_CH1. Safe.
GPIO0LeftADCPWM
ADC1_CH0. Safe.
GPIO10RightPWM
Safe everyday pin.
GPIO9RightPWMStrapping
⚠ BOOT strapping (the on-board BOOT button). Your circuit can block flashing.
GPIO8RightPWMStrapping
⚠ Strapping: must be HIGH at reset. The on-board blue LED often sits here.
GPIO7RightPWM
Safe. Default SPI SS.
GPIO6RightPWM
Safe. Default SPI MOSI.
GPIO5RightPWM
Safe. Default SPI MISO.
GNDRightPower
Ground.
3V3RightPower
3.3V rail (second pin for wiring convenience).
Quick matrices
| Function | Pins |
|---|---|
| ADC1 (all WiFi-safe) | GPIO 0 (CH0), 1 (CH1), 2 (CH2), 3 (CH3), 4 (CH4) |
| Touch | None: the ESP32-C3 has no touch peripheral |
| PWM (LEDC) | Any GPIO 0–10 |
| I²C defaults (Wire) | SDA = GPIO 8, SCL = GPIO 9 (both strapping, so remap to 0/1 or 6/7) |
| SPI (FSPI) | SCK = 4, MISO = 5, MOSI = 6, SS = 7 (flexible via the pin matrix) |
| UART0 (USB serial) | TX = GPIO 21, RX = GPIO 20 (on-module USB bridge); any other pair is possible via the matrix |
| DAC | None: use PWM and an RC filter for audio |
| USB native | GPIO 18 (D−) / GPIO 19 (D+), the on-board USB-C; don't rewire |
| Strapping | GPIO 2 (low at boot), GPIO 8 (high at boot), GPIO 9 (BOOT button) |
FAQ
Which pins are safe at boot?
GPIO 0, 1, 3, 4, 5, 6, 7, 10 are unconditionally safe. GPIO 2/8/9 work for outputs but keep their boot-time levels in mind; GPIO 11+ are off-limits.
Why does my C3 not flash with something wired?
Nine times out of ten it is GPIO 9 (BOOT) pulled by your circuit (disconnect it during flashing), or GPIO 2/8 strapped wrong.
Can I read analog while WiFi is on?
Yes. The C3's single ADC has no WiFi conflict, unlike the classic ESP32's ADC2. Use GPIO 0–4.
Data follows the Espressif ESP32-C3 datasheet. Always confirm against your board's schematic.
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