Adafruit GEMMA M0

Overview

The Adafruit GEMMA M0 is a miniature, coin-shaped microcontroller board built around the ATSAMD21E18 ARM Cortex M0+ processor running at 48 MHz. Measuring just 27.95mm in diameter, it is purpose-designed for wearable electronics and e-textile applications where small size and sew-ability are essential.

The board ships with CircuitPython pre-loaded, making it beginner-friendly — simply connect via USB, open the drive that appears, and edit code.py to get started. It is also fully compatible with the Arduino IDE for users who prefer a traditional C++ workflow. A built-in RGB DotStar LED is accessible from any programming environment.

Three large sew pads provide I/O, power, and ground connections compatible with conductive thread, enabling projects like light-up costumes, smart accessories, and interactive textiles. The pads support analog input, digital I/O, PWM output, capacitive touch sensing, and one analog output (DAC). An on/off switch and JST battery connector make it easy to run from a coin cell or small LiPo pack.

Hardware peripherals include native I2C and UART, 256 KB of flash, and 32 KB of SRAM. Despite its small footprint, the GEMMA M0 is a capable platform for animations, sensor reading, and simple control tasks — all in a package small enough to sew onto a garment.