# Adafruit GEMMA M0

> Coin-sized wearable microcontroller board with ATSAMD21E18 Cortex M0+ at 48MHz, 3 I/O sew pads, built-in RGB DotStar LED, and CircuitPython pre-installed. Designed for e-textiles and wearable projects.

## Quick Facts

- **Brand:** Adafruit
- **Board Type:** dev-board
- **Price:** ~$9.95
- **Product Readiness:** consumer
- **CPU:** ATSAMD21E18 ARM Cortex M0+
- **CPU Architecture:** ARM Cortex-M0+
- **CPU Cores:** 1
- **RAM:** 32 KB
- **Flash:** 256 KB
- **Power:** 5V via Micro USB or LiPo battery via JST connector
- **Operating Voltage:** 3.3V
- **Dimensions:** 27.95mm × 27.95mm × 6.4mm
- **Weight:** 2.1g

## Open Source

- **Firmware:** Yes
- **Schematics:** Yes
- **PCB Layout:** Yes

## Compatible Firmware

circuitpython, arduino

## Use Cases

- wearable
- e-textiles
- led-art
- education
- prototyping

## Components

- **ATSAMD21E18** (mcu): 32-bit ARM Cortex M0+ microcontroller at 48 MHz with 256 KB flash and 32 KB SRAM. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FSAM-D21DA1-Family-Data-Sheet-DS40001882G.pdf&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)
- **APA102 DotStar** (led): Built-in RGB DotStar LED for status indication and animations. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-shop.adafruit.com%2Fproduct-files%2F2343%2FSK9822_FINAL.pdf&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)

## Protocols

- **I2C**: SDA: D0, SCL: D1
- **SPI**: MOSI: D3, MISO: D4, SCK: D2
- **UART**: TX: D1, RX: D0

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| D0 | SDA | I2C | digital-input, digital-output, analog-input, touch |
| D1 | SCL | I2C | digital-input, digital-output, pwm, touch, dac |
| D2 | ADC | — | digital-input, digital-output, analog-input, touch |
| D3 | MOSI | SPI | digital-input, digital-output, pwm |
| D4 | MISO | SPI | digital-input, digital-output |

## Available Software

- **[CircuitPython]()** (open-source)
- **[Arduino]()** (open-source)

## Description

## 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.

## Where to Buy

- [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3501&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export) — 9.95

## Resources

- [product page](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3501&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)
- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3501&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)
- [documentation](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-gemma-m0%2Foverview&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)
- [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit-GEMMA-M0-PCB&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)
- [schematic](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit-GEMMA-M0-PCB%2Fblob%2Fmaster%2FAdafruit%2520Gemma%2520M0.sch&ref=openhardware.directory&product=adafruit-gemma-m0&source=md-export)

## Tags

`wearable`, `circuitpython`, `arduino`, `atsamd21`, `cortex-m0`, `adafruit`, `gemma`, `e-textiles`

## Images

![Adafruit GEMMA M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-gemma-m0/27d23cceb797.jpg)
![Adafruit GEMMA M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-gemma-m0/c87664102f72.jpg)
![Adafruit GEMMA M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-gemma-m0/91488af4ecbb.jpg)
![Adafruit GEMMA M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-gemma-m0/506fc913d9e8.jpg)

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