circuitpython/README.rst

Adafruit CircuitPython
======================

|Build Status| |Doc Status| |Discord|

`Status <#status>`__ \| `Supported Boards <#supported-boards>`__
\| `Download <#download>`__ \|
`Documentation <#documentation>`__ \|
`Contributing <#contributing>`__ \| `Differences from
Micropython <#differences-from-micropython>`__ \| `Project
Structure <#project-structure>`__

**CircuitPython** is an *education friendly* open source derivative of
`MicroPython <https://micropython.org>`_. CircuitPython supports use
on educational development boards designed and sold by
`Adafruit <https://adafruit.com>`_. Adafruit CircuitPython features
unified Python core APIs and a growing list of Adafruit libraries and
drivers of that work with it.

Status
------

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
~~~~~~~~~~~~~~~~~~~~~~~~~~

-  `Adafruit CircuitPlayground
   Express <https://www.adafruit.com/product/3333>`__
-  `Adafruit Feather M0
   Express <https://www.adafruit.com/product/3403>`__
-  `Adafruit Metro M0 Express <https://www.adafruit.com/product/3505>`__
-  `Adafruit Gemma M0 <https://www.adafruit.com/product/3501>`__

Other
~~~~~

-  `Adafruit Feather HUZZAH <https://www.adafruit.com/products/2821>`__
-  `Adafruit Feather M0
   Basic <https://www.adafruit.com/products/2772>`__
-  `Adafruit Feather M0 Bluefruit
   LE <https://www.adafruit.com/products/2995>`__ (uses M0 Basic
   binaries)
-  `Adafruit Feather M0
   Adalogger <https://www.adafruit.com/product/2796>`__ (MicroSD card
   supported using the `Adafruit CircuitPython SD
   library <https://github.com/adafruit/Adafruit_CircuitPython_SD>`__)
-  `Arduino Zero <https://www.arduino.cc/en/Main/ArduinoBoardZero>`__

Download
--------

Official binaries are available through the `latest GitHub
releases <https://github.com/adafruit/circuitpython/releases>`__.
Continuous (one per commit) builds are available
`here <https://adafruit-circuit-python.s3.amazonaws.com/index.html?prefix=bin>`__
and includes experimental hardware support.

Documentation
-------------

Guides and videos are available through the `Adafruit Learning
System <https://learn.adafruit.com/>`__ under the `CircuitPython
category <https://learn.adafruit.com/category/circuitpython>`__ and
`MicroPython
category <https://learn.adafruit.com/category/micropython>`__. An API
reference is also available on `Read the
Docs <http://circuitpython.readthedocs.io/en/latest/?>`__.

Contributing
------------

See
`CONTRIBUTING.md <https://github.com/adafruit/circuitpython/blob/master/CONTRIBUTING.md>`__
for full guidelines but please be aware that by contributing to this
project you are agreeing to the `Code of
Conduct <https://github.com/adafruit/circuitpython/blob/master/CODE_OF_CONDUCT.md>`__.
Contributors who follow the `Code of
Conduct <https://github.com/adafruit/circuitpython/blob/master/CODE_OF_CONDUCT.md>`__
are welcome to submit pull requests and they will be promptly reviewed
by project admins. Please join the `Gitter
chat <https://gitter.im/adafruit/circuitpython>`__ or
`Discord <https://discord.gg/nBQh6qu>`__ too.

--------------

Differences from `MicroPython <https://github.com/micropython/micropython>`__
-----------------------------------------------------------------------------

CircuitPython:

-  includes a port for Atmel SAMD21 (Commonly known as M0 in Adafruit
   product names.)
-  supports only Atmel SAMD21 and ESP8266 ports.
-  tracks MicroPython's releases (not master).

Behavior
~~~~~~~~

-  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.
-  ``boot.py`` (or ``settings.py``) 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``.
-  ``code.py`` (or ``main.py``) 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
   ``code.py`` in the REPL anymore.** CircuitPython's goal for this
   change includes reduce confusion about pins and memory being used.
-  After ``code.py`` the REPL can be entered by pressing any key. It no
   longer shares state with ``code.py`` 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.

API
~~~

-  Unified hardware APIs: `audioio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/audioio/__init__.html>`_, `analogio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/analogio/__init__.html>`_, `busio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/busio/__init__.html>`_, `digitalio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/digitalio/__init__.html>`_, `pulseio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/pulseio/__init__.html>`_, `touchio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/touchio/__init__.html>`_, `microcontroller <https://circuitpython.readthedocs.io/en/latest/shared-bindings/microcontroller/__init__.html>`_, `board <https://circuitpython.readthedocs.io/en/latest/shared-bindings/board/__init__.html>`_, `bitbangio <https://circuitpython.readthedocs.io/en/latest/shared-bindings/bitbangio/__init__.html>`_
-  No ``machine`` API on Atmel SAMD21 port.

Modules
~~~~~~~

-  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 <https://circuitpython.readthedocs.io/en/latest/shared-bindings/time/__init__.html>`__
   of their `CPython
   version <https://docs.python.org/3.4/library/time.html?highlight=time#module-time>`__.
   Therefore, code from CircuitPython is runnable on CPython but not
   necessarily the reverse.
-  tick count is available as
   `time.monotonic() <https://circuitpython.readthedocs.io/en/latest/shared-bindings/time/__init__.html#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``, ``code.py``, ``main.py``,
   ``main.txt``
-  Boot is one of these: ``settings.txt``, ``settings.py``, ``boot.py``,
   ``boot.txt``

--------------

Project Structure
-----------------

Here is an overview of the top-level source code directories.

Core
~~~~

The core code of
`MicroPython <https://github.com/micropython/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 pyboard.py module.

Ports
~~~~~

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 <https://www.arduino.cc/en/Main/ArduinoBoardZero>`__, `Adafruit
   Feather M0 Basic <https://www.adafruit.com/products/2772>`__, and
   `Adafruit Feather M0 Bluefruit
   LE <https://www.adafruit.com/products/2995>`__.
-  ``bare-arm`` A bare minimum version of MicroPython for ARM MCUs.
-  ``cc3200`` Support for boards based
   `CC3200 <http://www.ti.com/product/CC3200>`__ from TI such as the
   `WiPy 1.0 <https://www.pycom.io/solutions/py-boards/wipy1/>`__.
-  ``esp8266`` Support for boards based on ESP8266 WiFi modules such as
   the `Adafruit Feather
   HUZZAH <https://www.adafruit.com/products/2821>`__.
-  ``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 <https://qemu.org>`__.
-  ``stmhal`` Support for boards based on STM32 microcontrollers
   including the MicroPython flagship
   `PyBoard <https://store.micropython.org/store/#/products/PYBv1_1>`__.
-  ``teensy`` Support for the Teensy line of boards such as the `Teensy
   3.1 <https://www.pjrc.com/teensy/teensy31.html>`__.
-  ``unix`` Support for UNIX.
-  ``windows`` Support for
   `Windows <https://www.microsoft.com/en-us/windows/>`__.
-  ``zephyr`` Support for `Zephyr <https://www.zephyrproject.org/>`__, 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 <https://github.com/micropython/micropython>`__ parent
project.

`⬆ back to top <#adafruit-circuitpython>`__

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