# Adafruit Feather M0 Adalogger > Feather-format ATSAMD21 ARM Cortex-M0+ data logger at 48 MHz, 3.3V with microSD slot, 256KB flash, 32KB RAM, LiPo charging, native USB, and 12-bit ADC — 32-bit power for field data collection. ## 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:** 5.3g - **SD Card:** microSD ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Compatible Firmware arduino, circuitpython, platformio ## Use Cases - data-logging - portable - battery-powered - environmental-monitoring - field-research ## Components - **ATSAMD21G18** (mcu): Microchip ARM Cortex-M0+ at 48 MHz, 256KB flash, 32KB RAM, native USB, 12-bit ADC/DAC — [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-adalogger&source=md-export) - **MCP73831** (charger): Microchip MCP73831 100mA LiPo 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-adalogger&source=md-export) ## Protocols - **UART**: TX: D1, RX: D0 - **SPI**: MOSI: D23, MISO: D22, SCK: D24, SS: D10, SD_CS: D4 - **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 | | D4 | microSD Chip Select (SPI) | SPI | digital-input, digital-output | | 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 | | D8 | Green status LED, PWM | — | digital-input, digital-output, pwm | | 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 Adalogger combines the 32-bit ARM Cortex-M0+ performance of the Feather M0 platform with an integrated microSD card slot for data logging. Based on the ATSAMD21G18 at 48 MHz with 256KB flash and 32KB RAM, it offers significantly more processing power and memory than AVR-based Adalogger variants while maintaining the compact Feather form factor (51 × 23 mm, 5.3g). The microSD slot enables onboard storage for sensor readings, GPS coordinates, environmental data, and other time-series records. A green LED on pin 8 serves as a logging indicator alongside the standard red LED. The 12-bit ADC (versus 10-bit on AVR boards), 10-bit DAC, and PWM capability on all pins expand sensor and actuator options compared to 8-bit platforms. USB is handled natively by the ATSAMD21, enabling drag-and-drop CircuitPython firmware installation and USB serial monitoring. The integrated 100mA LiPoly charger manages 3.7V LiPo battery charging with automatic USB/battery switchover. The 3.3V regulator provides 500mA peak output. As a CircuitPython-capable board, the M0 Adalogger supports the Python `storage` module for direct filesystem access to the microSD card, making data logging accessible without C/C++ file I/O boilerplate. It stacks with all FeatherWing accessories through the standard Feather header system. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2796&ref=openhardware.directory&product=adafruit-feather-m0-adalogger&source=md-export) — 19.95 ## Resources - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2796&ref=openhardware.directory&product=adafruit-feather-m0-adalogger&source=md-export) - [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-feather-m0-adalogger&ref=openhardware.directory&product=adafruit-feather-m0-adalogger&source=md-export) ## Tags `feather`, `atsamd21`, `arm`, `cortex-m0`, `data-logging`, `microsd`, `circuitpython`, `adafruit` ## Images ![Adafruit Feather M0 Adalogger](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-adalogger/35fe29628fce.jpg) ![Adafruit Feather M0 Adalogger](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-feather-m0-adalogger/18cdae1bd7f9.jpg) --- [View full device page](https://openhardware.directory/devices/adafruit-feather-m0-adalogger)