Adafruit CircuitPython

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This is an open source derivative of MicroPython for use on educational development boards designed and sold by Adafruit including the Arduino Zero, Adafruit Feather M0 Basic, Adafruit Feather HUZZAH and Adafruit Feather M0 Bluefruit LE.

As a MicroPython derivative, this implements Python 3.x on microcontrollers such as the SAMD21 and ESP8266.

Project Status

This project is in beta. Most APIs should be stable going forward.


Guides and videos are available through the Adafruit Learning System under the CircuitPython category and MicroPython category. An API reference is also available on Read the Docs.


See for full guidelines but please be aware that by contributing to this project you are agreeing to the Code of Conduct. Contributors who follow the Code of Conduct are welcome to submit pull requests and they will be promptly reviewed by project admins. Please join the Gitter chat too.

Differences from MicroPython

  • Port for Atmel SAMD21 (Commonly known as M0 in product names.)
  • No machine API on Atmel SAMD21 port.
  • Only supports Atmel SAMD21 and ESP8266 ports.
  • Unified hardware API: nativeio, microcontroller, board, bitbangio (Only available on atmel-samd21 and ESP8266 currently.)
  • Tracks MicroPython’s releases (not master).
  • No module aliasing. (uos and utime are not available as os and time respectively.)
  • Modules with a CPython counterpart, such as time, are strict subsets of their CPython version. Therefore, code from CircuitPython is runnable on CPython but not necessarily the reverse.
  • tick count is available as time.monotonic()
  • os only available as uos
  • atmel-samd21 features
    • RGB status LED
    • Auto-reset after file write over mass storage. (Disable with samd.disable_autoreset())
    • Wait state after boot and main run, before REPL.
    • Main is one of these: code.txt,,, main.txt
    • Boot is one of these: settings.txt,,, boot.txt

Project Structure

Here is an overview of the top-level directories.


The core code of MicroPython is shared amongst ports including CircuitPython:

  • docs High level user documentation in Sphinx reStructuredText format.
  • drivers External device drivers written in Python.
  • examples A few example Python scripts.
  • extmod Shared C code used in multiple ports’ modules.
  • lib Shared core C code including externally developed libraries such as FATFS.
  • logo The MicroPython logo.
  • mpy-cross A cross compiler that converts Python files to byte code prior to being run in MicroPython. Useful for reducing library size.
  • py Core Python implementation, including compiler, runtime, and core library.
  • shared-bindings Shared definition of Python modules, their docs and backing C APIs. Ports must implement the C API to support the corresponding module.
  • tests Test framework and test scripts.
  • tools Various tools, including the module.


Ports include the code unique to a microcontroller line and also variations based on the board.

  • atmel-samd Support for SAMD21 based boards such as Arduino Zero, Adafruit Feather M0 Basic, and Adafruit Feather M0 Bluefruit LE.
  • bare-arm A bare minimum version of MicroPython for ARM MCUs.
  • cc3200 Support for boards based CC3200 from TI such as the WiPy 1.0.
  • esp8266 Support for boards based on ESP8266 WiFi modules such as the Adafruit Feather HUZZAH.
  • minimal A minimal MicroPython port. Start with this if you want to port MicroPython to another microcontroller.
  • pic16bit Support for 16-bit PIC microcontrollers.
  • qemu-arm Support for ARM emulation through QEMU.
  • stmhal Support for boards based on STM32 microcontrollers including the MicroPython flagship PyBoard.
  • teensy Support for the Teensy line of boards such as the Teensy 3.1.
  • unix Support for UNIX.
  • windows Support for Windows.
  • zephyr Support for Zephyr, a real-time operating system by the Linux Foundation.

CircuitPython only maintains the atmel-samd and esp8266 ports. The rest are here to maintain compatibility with the MicroPython parent project.