CircuitPython - a Python implementation for teaching coding with microcontrollers
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Adafruit CircuitPython

Build Status Doc Status Discord

Status | Supported Boards | Download | Documentation | Contributing | Differences from Micropython | Project Structure

CircuitPython is an education friendly open source derivative of MicroPython. CircuitPython supports use on educational development boards designed and sold by Adafruit. Adafruit CircuitPython features unified Python core APIs and a growing list of Adafruit libraries and drivers of that work with it.


This project is stable. Most APIs should be stable going forward. Those that change will change on major version numbers such as 2.0.0 and 3.0.0.

Supported Boards

Designed for CircuitPython



Official binaries are available through the latest GitHub releases. Continuous (one per commit) builds are available here and includes experimental hardware support.


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. A collection of awesome resources can be found at Awesome CircuitPython.

Specifically useful documentation when starting out:


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 Discord too.

Differences from MicroPython


  • includes a ports for MicroChip SAMD21 (Commonly known as M0 in Adafruit product names) and SAMD51 (M4).
  • supports only SAMD21, SAMD51, and ESP8266 ports. An nRF port is under development.
  • tracks MicroPython's releases (not master).
  • Longints (arbitrary-length integers) are enabled for most M0 Express boards (those boards with SPI flash chips external to the microcontroller), and for all M4 builds. Longints are disabled on other boards due to lack of flash space.


  • The order that files are run and the state that is shared between them. CircuitPython's goal is to clarify the role of each file and make each file independent from each other.
  • (or runs only once on start up before USB is initialized. This lays the ground work for configuring USB at startup rather than it being fixed. Since serial is not available, output is written to boot_out.txt.
  • (or is run after every reload until it finishes or is interrupted. After it is done running, the vm and hardware is reinitialized. This means you cannot read state from ```` in the REPL anymore. CircuitPython's goal for this change includes reduce confusion about pins and memory being used.
  • After the REPL can be entered by pressing any key. It no longer shares state with so it is a fresh vm.
  • Autoreload state will be maintained across reload.
  • Adds a safe mode that does not run user code after a hard crash or brown out. The hope is that this will make it easier to fix code that causes nasty crashes by making it available through mass storage after the crash. A reset (the button) is needed after its fixed to get back into normal mode.



  • No module aliasing. (uos and utime are not available as os and time respectively.) Instead os, time, and random are CPython compatible.
  • New storage module which manages file system mounts. (Functionality from uos in MicroPython.)
  • Modules with a CPython counterpart, such as time, os and random, 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()

atmel-samd21 features

  • RGB status LED
  • Auto-reload after file write over mass storage. (Disable with samd.disable_autoreload())
  • 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 source code 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.
  • shared-module Shared implementation of Python modules that may be based on common-hal.
  • 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.

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