# Adafruit Trinket M0

> Ultra-compact ATSAMD21E18 ARM Cortex-M0+ board at 48 MHz with 256KB flash, 32KB RAM, 5 GPIO pins, built-in RGB DotStar LED, capacitive touch, native USB, and CircuitPython support. Weighs just 1.4g in 27mm × 15mm form factor.

## Quick Facts

- **Brand:** Adafruit
- **Board Type:** dev-board
- **Price:** ~$8.95
- **Product Readiness:** developer
- **CPU:** ATSAMD21E18 ARM Cortex-M0+ @ 48 MHz
- **CPU Architecture:** ARM Cortex-M0+
- **CPU Cores:** 1
- **RAM:** 32KB SRAM
- **Flash:** 256KB
- **Power:** 5V via USB or external pin
- **Operating Voltage:** 3.3V
- **Dimensions:** 27 × 15.3 × 2.75 mm
- **Weight:** 1.4g
- **Antenna:** none

## Open Source

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

## Compatible Firmware

arduino, circuitpython

## Use Cases

- wearable
- prototyping
- circuitpython-learning
- compact-iot-node
- educational-platform

## Components

- **ATSAMD21E18** (mcu): ARM Cortex-M0+ at 48MHz, 256KB flash, 32KB SRAM, native USB supporting serial/HID/MIDI. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F044%2F363%2Foriginal%2Fsamd21.pdf&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)

## Protocols

- **SPI**: MOSI: PA07, MISO: PA06
- **I2C**: SDA: PA06, SCL: PA07
- **UART**: TX: PA02, RX: PA08
- **USB**: 

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| PA08 | D0 — GPIO / UART RX / Analog / Capacitive Touch | UART | digital-input, digital-output, analog-input |
| PA02 | D1 — GPIO / UART TX / Analog / Capacitive Touch / DAC | UART | digital-input, digital-output, analog-input, analog-output |
| PA09 | D2 — GPIO / Analog / Capacitive Touch | — | digital-input, digital-output, analog-input |
| PA07 | D3/SCL — GPIO / I2C SCL / PWM / SPI MOSI / Analog | I2C | digital-input, digital-output, analog-input, pwm |
| PA06 | D4/SDA — GPIO / I2C SDA / PWM / SPI MISO / Analog | I2C | digital-input, digital-output, analog-input, pwm |

## Description

## Overview

The Adafruit Trinket M0 is the smallest ARM Cortex-M0+ board in Adafruit's lineup, measuring just 27 × 15.3 mm and weighing 1.4 grams. Despite its tiny size, it runs the ATSAMD21E18 at 48 MHz with 256KB of flash and 32KB of SRAM — the same chip architecture used in the much larger Feather M0.

All five GPIO pins are independently usable (none are shared with USB), and all support 12-bit analog input. Three pins support hardware capacitive touch for touch-sensitive applications without any additional hardware. A true DAC output is available on one pin, and two high-speed PWM outputs are provided.

The built-in RGB DotStar LED (APA102-style) can be used for status indication or creative effects. The board also has a DMA-capable NeoPixel pin and enough memory to drive 8000+ NeoPixels or DotStars in sequence — despite the board's tiny size. A green power LED and red pin #13 LED round out the onboard indicators.

CircuitPython runs natively on the Trinket M0, allowing Python scripts to be developed without any compilation step — just copy a .py file onto the USB drive. The Arduino IDE is also fully supported. The Trinket M0 is ideal for small form factor projects, wearables, embedded installations, and anywhere you need a capable microcontroller in the smallest possible footprint.

## Where to Buy

- [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3500&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export) — 8.95

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3500&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)
- [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit-Trinket-M0-PCB&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-trinket-m0-circuitpython-arduino%2Foverview&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)
- [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F044%2F363%2Foriginal%2Fsamd21.pdf&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)
- [schematics](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F045%2F723%2Fmedium800%2Fadafruit_products_schem.png&ref=openhardware.directory&product=adafruit-trinket-m0&source=md-export)

## Tags

`trinket`, `atsamd21`, `arm-cortex-m0`, `circuitpython`, `dotstar`, `tiny`, `wearable`, `adafruit`

## Images

![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/2c6196e179ab.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/251611be7ac3.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/90b8f7a4dc1d.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/197dcd6f06bf.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/fd956260f65f.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/e004496fb191.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/abacb21e2627.jpg)
![Adafruit Trinket M0](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-m0/6c95d0cc50fc.jpg)

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