XIAO ESP32C3
Tiny ESP32-C3 board with USB-C and rich I/O - great for wearable tech, embedded controllers, and rapid prototyping.
Pinout
14 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 2 | D0A0GPIO2 | strapping | adc · pwm | |
| 2 | 3 | D1A1GPIO3 | safe | adc · pwm | |
| 3 | 4 | D2A2GPIO4 | strapping | adc · pwm | |
| 4 | 5 | D3A3GPIO5 | strapping | adc · pwm | ADC2; analog readings may be unreliable compared to ADC1 |
| 5 | 6 | D4SDAGPIO6 | strapping | i2c · pwm | |
| 6 | 7 | D5SCLGPIO7 | strapping | i2c · pwm | |
| 7 | 21 | D6TXGPIO21 | uart | uart · pwm | |
| 8 | - | 5V | power | - | 5V power input/output |
| 9 | - | GND | ground | - | |
| 10 | - | 3V3 | power | - | 3.3V power |
| 11 | 10 | D10MOSIGPIO10 | safe | spi · pwm | |
| 12 | 9 | D9MISOGPIO9 | strapping | spi · pwm | |
| 13 | 8 | D8SCKGPIO8 | strapping | spi · pwm | |
| 14 | 20 | D7RXGPIO20 | uart | uart · pwm |
Start with these
2 pins with no boot or system involvementFreely 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 |
|---|---|---|---|
| D0 | GPIO2 | Must be held high during boot (if low on reset, normal flash boot may fail) | Strapping |
| D2 | MTMS | Used during boot; JTAG TMS for debugging; acts as Quad-SPI flash IO (hold data line) in internal-flash variants | JTAG |
| D3 | MTDI | Used during boot; JTAG TDI for debugging; acts as Quad-SPI flash IO (write-protect data line) in internal-flash variants | JTAG |
| D4 | MTCK | Used during boot; JTAG TCK for debugging; provides flash clock in internal-flash variants | JTAG |
| D5 | MTDO | Used during boot; JTAG TDO for debugging; acts as Quad-SPI flash IO (data line) in internal-flash variants | JTAG |
| D6 | U0TXD | Used as UART0 transmit (console/bootloader); repurposing may disable serial console output and printing | UART |
| D9 | GPIO9 | Controls boot mode on reset (HIGH for normal flash boot, LOW enters serial download mode) | Strapping |
| D8 | GPIO8 | Must be held high during reset (if low, UART flashing/boot may not work) | Strapping |
| D7 | U0RXD | Used as UART0 receive (console/bootloader); repurposing may disable serial programming and debug logs | UART |
Pinout notes The XIAO ESP32C3 pinout brings out 14 pins at a 2.54 mm pitch - 11 usable GPIO alongside the 5V , GND and 3V3 power rails. Peripheral wiring is…
The XIAO ESP32C3 pinout brings out 14 pins at a 2.54 mm pitch - 11 usable GPIO alongside the 5V, GND and 3V3 power rails.
Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO6 and SCL on GPIO7; the SPI bus (MOSI, MISO, SCK) is broken out in full; TX/RX on GPIO21 and GPIO20 cover serial logging and flashing.
Beyond plain digital I/O you get 4 ADC-capable pins for sensors and battery monitoring and PWM on every GPIO.
9 of the exposed pins carry boot-time or system duties on the ESP32-C3 (D0, D2, D3 and 6 more) - check the guidance above before wiring anything to them. D1 and D10 are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutesBoard: Xiao Esp32c3
USB CDC On Boot: Enabled
Flash Size: 4MB · QIO
Upload Speed: 921600
// blink
pinMode(3, OUTPUT);
digitalWrite(3, LOW); // on (often inverted)[env:XIAO_ESP32C3]
platform = espressif32
board = esp32-c3-devkitm-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32-c3-devkitm-1
variant: XIAO_ESP32C3
framework:
type: esp-idf
# blink - GPIO3
output:
- platform: gpio
pin: 3
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32c3 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binSpecifications
ESP32-C3 · 21 × 17.5 mmAbout this board
At 21 × 17.5 mm it's the smallest ESP32-C3 board we've measured.
Inside sits the ESP32-C3 - a single-core RISC-V and the budget low-power pick.
The $10.00 price tag is typical for an ESP32-C3 board.
Around the module: battery charging, status LEDs (Charge) and Reset/Boot buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-C3 boards.
- Ultra-small form factor (21x17.5 mm)
- Low power consumption with deep sleep support
- Ships with an external u.FL antenna
- Onboard LiPo charge management via solder pads
Where to buy
prices are typical street pricesResources
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