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ESP32-C3 pinout & GPIO reference
The cheapest RISC-V option and the mainstream ESP8266 replacement. Few pins but enough, plus native USB. GPIO 11–17 are usually consumed by in-package flash — the biggest constraint on small designs.
Data verified：2026-10-20 · Cross-checked against Espressif datasheets and the ESP-IDF programming guide. Always confirm with the official document before finalizing a design.
Official documentation：link 1
Key specifications
| Core | 32-bit RISC-V single-core (RV32IMC) |
|---|---|
| Clock | Up to 160 MHz |
| SRAM | 400 KB |
| Wireless | Wi-Fi 802.11 b/g/n · Bluetooth 5 (LE) |
| USB | Native USB Serial/JTAG (GPIO18/19) |
| ADC | 12-bit SAR, 6 channels (GPIO0–5) |
| DAC | None |
| Touch | None |
| GPIO | 0–21 (~14 actually usable) |
| Security | Secure Boot · Flash encryption · crypto accelerators |
Traps that cost you a board respin
- GPIO 11–17 are occupied on in-package-flash variants; only 0–10 and 18–21 remain.
- GPIO 18/19 are USB Serial/JTAG — not usable as ordinary IO.
- No DAC and no touch peripheral: check for missing features when replacing an ESP8266.
- Strapping pins are GPIO 2 / 8 / 9; pulling GPIO9 low at reset enters download mode.
- Only 6 ADC channels, all on ADC1 — mind the timing conflict with Wi-Fi.
Full GPIO table
| GPIO | Status | Alternate functions |
|---|---|---|
GPIO0 | Usable | ADC1_CH0 |
GPIO1 | Usable | ADC1_CH1 |
GPIO2 | Usable | StrappingADC1_CH2 |
GPIO3 | Usable | ADC1_CH3 |
GPIO4 | Usable | ADC1_CH4 |
GPIO5 | Usable | ADC1_CH5 |
GPIO6 | Usable | General GPIO |
GPIO7 | Usable | General GPIO |
GPIO8 | Usable | Strapping |
GPIO9 | Usable | Strapping (low = download mode) |
GPIO10 | Usable | General GPIO |
GPIO11 | Unusable | Internal flash (usable with external flash) |
GPIO12 | Unusable | Internal flash (usable with external flash) |
GPIO13 | Unusable | Internal flash (usable with external flash) |
GPIO14 | Unusable | Internal flash (usable with external flash) |
GPIO15 | Unusable | Internal flash (usable with external flash) |
GPIO16 | Unusable | Internal flash (usable with external flash) |
GPIO17 | Unusable | Internal flash (usable with external flash) |
GPIO18 | Usable | USB D− (USB Serial/JTAG) |
GPIO19 | Usable | USB D+ (USB Serial/JTAG) |
GPIO20 | Usable | UART0 RX |
GPIO21 | Usable | UART0 TX |
Individual GPIO pages
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Peripheral guidesI²C · SPI · UART · RMT · LEDC · deep sleep