The Seeed Studio XIAO SAMD21 is the original member of the popular XIAO family: a very small, breadboard-friendly Arduino-compatible development board built around the Microchip SAMD21G18 microcontroller.
Despite its tiny 21 × 17.8 mm footprint, this module provides a useful set of interfaces for compact embedded projects, wearable electronics, sensor nodes, small automation projects, data loggers, and educational Arduino projects.
The heart of the module is a 32-bit Arm Cortex-M0+ processor running at up to 48Â MHz. It includes 256Â KB Flash memory and 32Â KB SRAM, which makes it a good step up from classic 8-bit Arduino boards while keeping power consumption low and the board size extremely compact.
Programming is supported through the Arduino IDE, PlatformIO, MicroPython, CircuitPython, and Zephyr. The USB-C connector is used for power and programming, so no external USB-to-serial adapter is required.
Key features
- Microchip SAMD21G18 microcontroller
- 32-bit Arm Cortex-M0+ processor, up to 48Â MHz
- 256Â KB Flash memory
- 32Â KB SRAM
- Ultra-compact XIAO form factor: 21 × 17.8 mm
- USB-C connector for power and programming
- 11 digital I/O pins
- 11 analog-capable pins
- 10 PWM-capable pins
- 1 true DAC output on D0 / A0
- I²C, SPI, and UART interfaces
- SWD pads for advanced debugging and programming
- Onboard user LED, power LED, and serial TX/RX indicator LEDs
- Breadboard-friendly layout
Technical specifications
| MCU | Microchip SAMD21G18 |
| CPU | Arm Cortex-M0+ 32-bit processor, up to 48Â MHz |
| Flash | 256Â KB |
| SRAM | 32Â KB |
| GPIO | 14 pins total, 11 user-accessible digital pins |
| Analog inputs | 11 analog-capable pins |
| PWM | 10 PWM-capable pins |
| DAC | 1 true analog output on D0 / A0 |
| Interfaces | I²C, SPI, UART, SWD |
| USB | USB Type-C for power and programming |
| Logic level | 3.3Â V |
| Power input | 5Â V via USB-C or 5Â V pin |
| Dimensions | Approx. 21 × 17.8 mm |
Important: The SAMD21 microcontroller uses 3.3Â V logic. Do not connect 5Â V signals directly to the GPIO pins.
This module can be used with our CANABLOX® development system. A suitable XIAO adapter board, such as CX-XIAO-S or CX-XIAO-MH, is required. It can also be added to our CANADUINO® PLC-300 V2 Programmable Logic Controller DIY kit to provide extended functionality.
For pinout, software setup, schematics, and additional documentation, please refer to the official Seeed Studio XIAO SAMD21 documentation:
