Adafruit (PID 3403) Feather M0 Express - Designed for CircuitPython - ATSAMD21 Cortex M0

Please note, CircuitPython is still in beta and we're working hard to make it awesome! Please pick up one of these Feather M0 Expresses if you want to try it out - maybe even help us find bugs and make improvements!

That doesn't mean you cant also use it with Arduino IDE! At the Feather M0's heart is an ATSAMD21G18 ARM Cortex M0+ processor, clocked at 48 MHz and at 3.3V logic, the same one used in the new Arduino Zero. This chip has a whopping 256K of FLASH (8x more than the Atmega328 or 32u4) and 32K of RAM (16x as much)! This chip comes with built in USB so it has USB-to-Serial program & debug capability built in with no need for an FTDI-like chip.

Here's some handy specs!
ATSAMD21G18 @ 48MHz with 3.3V logic/power
256KB of FLASH + 32KB of RAM. No EEPROM
32.768 KHz crystal for clock generation & RTC
3.3V regulator with 500mA peak current output
USB native support, comes with USB bootloader and serial port debugging
Built in 100mA lipoly charger with charging status indicator LED
Pin #13 red LED for general purpose blinking
Power/enable pin
4 mounting holes
Reset button

The Feather M0 Express uses the extra space left over to add a Mini NeoPixel, 2 MB SPI Flash storage and a little prototyping space. You can use the SPI Flash storage like a very tiny hard drive. When used in CircuitPython, the 2 MB flash acts as storage for all your scripts, libraries and files. When used in Arduino, you can read/write files to it, like a little datalogger or SD card, and then with our helper program, access the files over USB.