The New Adafruit Feather M4

Alasdair Allan
2 min readJul 16, 2018


I’ve been talking a lot recently about the success of high-level languages of microcontrollers, and why I think that maturing ecosystem around both Python and Javascript on embedded hardware is important.

Which is where the new Feather M4 Express comes in, the latest board in Adafruit’s Feather line, and the most powerful yet to support their open source fork of MicroPython, called CircuitPython, out of the box.

The new Feather M4 Express, the latest Adafruit board to support CircuitPython. (📷: Adafruit)

Measuring 2.0×0.9×0.28 inches (51×23×8 mm) without headers soldered on, and weighing just 5 grams, the new Feather M4 is built around the 32-bit Microchip ATSAMD51J19. It’s an Arm Cortex-M4 processor running at 120MHz with floating point and hardware DSP support, with 512KB of Flash and 192KB of RAM. There is also a built-in crypto engine with 256-bit AES, “true” RNG—although remember random numbers are hard—and a pubkey controller.

The board itself has a 2 MB QSPI (Quad SPI) Flash storage chip—located right next to the Arm processor—for file and code storage. While using the QSPI peripheral under the Arduino development environment requires a library, with CircuitPython the 2MB of Flash just shows up as the writeable disk drive.

This Feather is based on an ATSAMD51J19 —a Cortex-M4 running 120MHz with floating point support, 512KB Flash, and 192KB RAM. (📷: Adafruit)

It comes pre-loaded with the UF2 bootloader, which means it looks like a USB storage key. When you plug it in the board it will simply show up on your desktop as a external drive. Edit the Python file on the drive, in whatever text editor you want to use, and changes to your code are run as soon as the file is done saving. No installation, no compilers, no development environments.

The board exposes 21×GPIO pins, including a 12-bit DAC, and 12-bit ADC, hardware serial, SPI, I2C, I2S, and an 8-bit parallel capture controller—for video input. There’s also a 100mA LiPo charger hardware onboard so that you can run it, and your project, directly from a battery.

If you’ve been thinking about getting started and experimenting with high-level languages on an embedded boards, this could well be where you want to start. Released at the tail end of last week, the Feather M4 Express is available now for $22.95 plus shipping.