# Adafruit Feather M0 Express > ATSAMD21G18 ARM Cortex-M0+ Feather board with 2MB SPI flash for CircuitPython code storage, built-in NeoPixel, 256KB flash, 32KB RAM, native USB, and 100mA LiPo charger. The dedicated CircuitPython Feather. ## Quick Facts - **Brand:** Adafruit - **Board Type:** dev-board - **Price:** ~$19.95 - **Product Readiness:** developer - **CPU:** ATSAMD21G18 ARM Cortex-M0+ @ 48 MHz - **CPU Architecture:** ARM Cortex-M0+ - **CPU Cores:** 1 - **RAM:** 32KB SRAM - **Flash:** 256KB + 2MB SPI Flash - **Power:** 5V + LiPo - **Operating Voltage:** 3.3V - **Dimensions:** 51 × 22.8 × 7.3 mm - **Weight:** 4.7g - **Antenna:** none ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Compatible Firmware arduino, circuitpython ## Use Cases - prototyping - educational-platform - iot - circuitpython-learning ## Components - **ATSAMD21G18** (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%2Fwww.adafruit.com%2Fimages%2Fproduct-files%2F2772%2Fatmel-42181-sam-d21_datasheet.pdf&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) ## Protocols - **SPI**: MOSI: PA16, MISO: PA19, SCK: PA17 - **I2C**: SDA: PA22, SCL: PA23 - **UART**: TX: PA10, RX: PA11 - **USB**: ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | PA11 | RX — UART Receive | UART | digital-input, digital-output | | PA10 | TX — UART Transmit | UART | digital-input, digital-output | | PA15 | D5 — GPIO / PWM | — | digital-input, digital-output, pwm | | PA20 | D6 — GPIO / PWM | — | digital-input, digital-output, pwm | | PA07 | D9 — GPIO / PWM / Analog | — | digital-input, digital-output, pwm, analog-input | | PA18 | D10 — GPIO / PWM | — | digital-input, digital-output, pwm | | PA16 | D11 — SPI MOSI | SPI | digital-input, digital-output | | PA19 | D12 — SPI MISO | SPI | digital-input, digital-output | | PA17 | D13 — SPI SCK / LED | SPI | digital-input, digital-output | | PA22 | SDA — I2C Data | I2C | digital-input, digital-output | | PA23 | SCL — I2C Clock | I2C | digital-input, digital-output | | PA02 | A0 — Analog In / DAC Out | — | analog-input, analog-output | | PB08 | A1 — Analog In | — | analog-input | | PB09 | A2 — Analog In | — | analog-input | | PA04 | A3 — Analog In | — | analog-input | | PA05 | A4 — Analog In | — | analog-input | | PB02 | A5 — Analog In | — | analog-input | ## Description ## Overview The Adafruit Feather M0 Express is designed specifically to be the best CircuitPython platform in the Feather lineup. It combines the ATSAMD21G18 ARM Cortex-M0+ at 48 MHz with 2MB of SPI flash storage — enough space to hold CircuitPython itself, all necessary libraries, and user code files simultaneously, accessible as a USB drive. The M0 Express is functionally similar to the Feather M0 Basic, but the addition of 2MB SPI flash transforms the development experience: CircuitPython scripts live on the board's file system and execute immediately on power-up, no compilation or flashing required. Editing code is as simple as editing a .py file on a USB drive. A built-in RGB NeoPixel LED provides visual feedback for debugging and status indication without external components. All other standard Feather features are present: 20 GPIO pins, 6 analog inputs (12-bit ADC), one analog output (10-bit DAC), hardware SPI/I2C/UART, native USB, and a 100mA LiPo charger with JST connector. The board is fully compatible with both CircuitPython and the Arduino IDE. For CircuitPython users, Adafruit's extensive library ecosystem and online learning guides make this the ideal starting point for Python-based microcontroller projects. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3403&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) — 19.95 ## Resources - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3403&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) - [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit-Feather-M0-Express-PCB&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) - [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-feather-m0-express-designed-for-circuit-python-circuitpython%2Foverview&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) - [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fimages%2Fproduct-files%2F2772%2Fatmel-42181-sam-d21_datasheet.pdf&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) - [schematics](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F040%2F553%2Fmedium800%2Farduino_schem.png&ref=openhardware.directory&product=adafruit-feather-m0-express&source=md-export) ## Tags `feather`, `circuitpython`, `atsamd21`, `arm-cortex-m0`, `neopixel`, `2mb-flash`, `lipo-charger`, `adafruit` ## Images ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/cd144f32874d.jpg) ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/77ca1da1773d.jpg) ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/2157be9de71e.jpg) ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/126ff0f14e3b.jpg) ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/5ff91b4a164d.jpg) ![Adafruit Feather M0 Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-express/020bca9e6428.jpg) --- [View full device page](https://openhardware.directory/devices/adafruit-feather-m0-express)