# Adafruit Feather M0 Basic Proto > Feather-format ATSAMD21 ARM Cortex-M0+ board at 48 MHz, 3.3V with 256KB flash, 32KB RAM, LiPo charging, native USB, 12-bit ADC/DAC, and RTC crystal — lightweight and CircuitPython-capable. ## 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:** 32 KB - **Flash:** 256 KB - **Power:** 3.7V LiPo via JST or 5V Micro USB - **Operating Voltage:** 3.3V - **Dimensions:** 51 × 23 mm - **Weight:** 4.6g ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Compatible Firmware arduino, circuitpython, platformio ## Use Cases - portable - battery-powered - data-logging - audio - iot - prototyping ## Components - **ATSAMD21G18** (mcu): Microchip ARM Cortex-M0+ at 48 MHz, 256KB flash, 32KB RAM, native USB, 12-bit ADC/DAC, hardware RTC — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FSAM_D21_DA1_Family_DataSheet_DS40001882H.pdf&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) - **MCP73831** (charger): Microchip MCP73831 100mA LiPo/LiIon charge management IC — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2F20001984g.pdf&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) ## Protocols - **UART**: TX: D1, RX: D0 - **SPI**: MOSI: D23, MISO: D22, SCK: D24, SS: D10 - **I2C**: SDA: D20, SCL: D21 - **USB** ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | D0 | UART RX | UART | digital-input, digital-output | | D1 | UART TX | UART | digital-input, digital-output | | D2 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D3 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D4 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D5 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D6 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D7 | Digital I/O, Interrupt | — | digital-input, digital-output, interrupt | | D9 | Battery voltage monitor, Analog Input (A7), PWM | — | digital-input, digital-output, analog-input, pwm | | D10 | SPI SS, PWM | SPI | digital-input, digital-output, pwm | | D11 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D12 | Digital I/O, PWM | — | digital-input, digital-output, pwm | | D13 | Onboard red LED, PWM | — | digital-input, digital-output, pwm | | D20 | I2C SDA — SAMD21 PA22 | I2C | digital-input, digital-output | | D21 | I2C SCL — SAMD21 PA23 | I2C | digital-input, digital-output | | D22 | SPI MISO — SAMD21 PA14 | SPI | digital-input, digital-output | | D23 | SPI MOSI — SAMD21 PA12 | SPI | digital-input, digital-output | | D24 | SPI SCK — SAMD21 PA13 | SPI | digital-input, digital-output | | A0 | 10-bit DAC Output, 12-bit Analog Input | — | analog-input, analog-output, digital-input, digital-output | | A1 | 12-bit Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A2 | 12-bit Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A3 | 12-bit Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A4 | 12-bit Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | | A5 | 12-bit Analog Input / Digital I/O | — | analog-input, digital-input, digital-output | ## Available Software - **[Arduino IDE]()** (open-source) - **[CircuitPython]()** (open-source) - **[PlatformIO]()** (open-source) ## Description ## Overview The Adafruit Feather M0 Basic Proto is a 32-bit ARM Cortex-M0+ development board in the Feather form factor, built around the Microchip ATSAMD21G18 running at 48 MHz. It represents a significant step up from AVR-based Feathers, offering 256KB of flash, 32KB of RAM, 12-bit ADC/DAC, and native USB support — all in a thin, lightweight 51 × 23 mm package at just 4.6 grams. The ATSAMD21 handles USB natively, enabling the board to appear as a USB disk drive for drag-and-drop CircuitPython firmware uploads. It also supports Arduino IDE via the Arduino SAMD board package, providing PWM on all pins, six 12-bit analog inputs, one 10-bit DAC output, and standard Serial, I2C, and SPI interfaces. A 32.768 kHz RTC crystal is included for timekeeping applications. An integrated 100mA LiPoly charger manages battery charging when USB power is present, with automatic switchover between battery and USB. The 3.3V regulator provides 500mA peak output. A small prototyping area with through-holes is included on the PCB for minor circuit additions. As the first Feather to support CircuitPython, the M0 Basic Proto established the SAMD21 as a core platform across dozens of Feather variants and FeatherWing accessories. Its combination of 32-bit performance, USB versatility, and compact size makes it suitable for data logging, audio, USB instruments, and battery-powered sensor nodes. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2772&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) — 19.95 ## Resources - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2772&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) - [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-feather-m0-basic-proto&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) - [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FSAM_D21_DA1_Family_DataSheet_DS40001882H.pdf&ref=openhardware.directory&product=adafruit-feather-m0-basic-proto&source=md-export) ## Tags `feather`, `atsamd21`, `arm`, `cortex-m0`, `circuitpython`, `adafruit`, `lipo`, `32-bit` ## Images ![Adafruit Feather M0 Basic Proto](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-basic-proto/f89c976e8856.jpg) ![Adafruit Feather M0 Basic Proto](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-basic-proto/bd8553018fe2.jpg) --- [View full device page](https://openhardware.directory/devices/adafruit-feather-m0-basic-proto)