Adafruit CircuitPython API Reference¶
Welcome to the API reference documentation for Adafruit CircuitPython. This contains low-level API reference docs which may link out to separate “getting started” guides. Adafruit has many excellent tutorials available through the Adafruit Learning System.
CircuitPython is a beginner friendly, open source version of Python for tiny, inexpensive
computers called microcontrollers. Microcontrollers are the brains of many electronics including a
wide variety of development boards used to build hobby projects and prototypes. CircuitPython in
electronics is one of the best ways to learn to code because it connects code to reality. Simply
install CircuitPython on a supported board via drag and drop and then edit a
code.py file on
the CIRCUITPY drive. The code will automatically reload. No software installs are needed besides a
text editor (we recommend Mu for beginners.)
CircuitPython features unified Python core APIs and a growing list of 150+ device libraries and drivers that work with it. These libraries also work on single board computers with regular Python via the Adafruit Blinka Library.
CircuitPython is based on MicroPython. See below for differences. CircuitPython development is sponsored by Adafruit and is available on their educational development boards. Please support both MicroPython and Adafruit.
Official binaries for all supported boards are available through circuitpython.org/downloads. The site includes stable, unstable and continuous builds. Full release notes and assets are available through GitHub releases as well.
Guides and videos are available through the Adafruit Learning System under the CircuitPython 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 CONTRIBUTING.md 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.
While we are happy to see CircuitPython forked and modified, we’d appreciate it if forked releases not use the name “CircuitPython” or the Blinka logo. “CircuitPython” means something special to us and those who learn about it. As a result, we’d like to make sure products referring to it meet a common set of requirements.
If you’d like to use the term “CircuitPython” and Blinka for your product here is what we ask:
- Your product is supported by the primary “adafruit/circuitpython” repo. This way we can update any custom code as we update the CircuitPython internals.
- Your product is listed on circuitpython.org (source here). This is to ensure that a user of your product can always download the latest version of CircuitPython from the standard place.
- Your product has a user accessible USB plug which appears as a CIRCUITPY drive when plugged in.
If you choose not to meet these requirements, then we ask you call your version of CircuitPython something else (for example, SuperDuperPython) and not use the Blinka logo. You can say it is “CircuitPython-compatible” if most CircuitPython drivers will work with it.
Differences from MicroPython¶
- Supports native USB on all boards, allowing file editing without special tools.
- Supports only SAMD21, SAMD51, nRF52840, CXD56, STM32F4 and i.MX RT ports.
- Floats (aka decimals) are enabled for all builds.
- Error messages are translated into 10+ languages.
- Does not support concurrency within Python (including interrupts and threading). Some concurrency is achieved with native modules for tasks that require it such as audio file playback.
- 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.
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
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.pyin the REPL anymore. CircuitPython’s goal for this change includes reduce confusion about pins and memory being used.
code.pythe REPL can be entered by pressing any key. It no longer shares state with
code.pyso 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.
- RGB status LED indicating CircuitPython state, and errors through a sequence of colored flashes.
code.pyor other main file after file system writes over USB mass storage. (Disable with
- Entering the REPL after the main code is finished requires a key press which enters the REPL and disables autoreload.
- Main is one of these:
- Boot is one of these:
- Unified hardware APIs. Documented on ReadTheDocs.
- API docs are rST within the C files in
- No module aliasing. (
utimeare not available as
randomare CPython compatible.
storagemodule which manages file system mounts. (Functionality from
- Modules with a CPython counterpart, such as
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()
Here is an overview of the top-level source code directories.
The core code of MicroPython is shared amongst ports including CircuitPython:
docsHigh level user documentation in Sphinx reStructuredText format.
driversExternal device drivers written in Python.
examplesA few example Python scripts.
extmodShared C code used in multiple ports’ modules.
libShared core C code including externally developed libraries such as FATFS.
logoThe CircuitPython logo.
mpy-crossA cross compiler that converts Python files to byte code prior to being run in MicroPython. Useful for reducing library size.
pyCore Python implementation, including compiler, runtime, and core library.
shared-bindingsShared definition of Python modules, their docs and backing C APIs. Ports must implement the C API to support the corresponding module.
shared-moduleShared implementation of Python modules that may be based on
testsTest framework and test scripts.
toolsVarious tools, including the pyboard.py module.
Ports include the code unique to a microcontroller line and also variations based on the board.
atmel-samdSupport for SAMD21 and SAMD51 based boards.
nrfSupport for the nRF52840 based boards.
unixSupport for UNIX. Only used for automated testing.
The remaining port directories not listed above are in the repo to maintain compatibility with the MicroPython parent project.
Full Table of Contents¶
- Core Modules
_bleio– Bluetooth Low Energy (BLE) communication
_eve– Low-level BridgeTek EVE bindings
_pew– LED matrix driver
_pixelbuf– A fast RGB(W) pixel buffer library for like NeoPixel and DotStar
_stage– C-level helpers for animation of sprites on a stage
_typing– Types for the C-level protocols
aesio– AES encryption routines
analogio– Analog hardware support
audiobusio– Support for audio input and output over digital buses
audiocore– Support for audio samples
audioio– Support for audio output
audiomixer– Support for audio mixing
audiomp3– Support for MP3-compressed audio files
audiopwmio– Audio output via digital PWM
bitbangio– Digital protocols implemented by the CPU
board– Board specific pin names
busio– Hardware accelerated external bus access
camera– Support for camera input
canio– CAN bus access
countio– Support for edge counting
digitalio– Basic digital pin support
displayio– Native helpers for driving displays
fontio– Core font related data structures
framebufferio– Native framebuffer display driving
frequencyio– Support for frequency based protocols
gamepad– Button handling in the background
gamepadshift– Tracks button presses read through a shift register
gnss– Global Navigation Satellite System
i2cperipheral– Two wire serial protocol peripheral
math– mathematical functions
memorymonitor– Memory monitoring helpers
microcontroller– Pin references and cpu functionality
multiterminal– Manage additional terminal sources
neopixel_write– Low-level neopixel implementation
network– Network Interface Management
nvm– Non-volatile memory
os– functions that an OS normally provides
ps2io– Support for PS/2 protocol
pulseio– Support for individual pulse based protocols
pwmio– Support for PWM based protocols
random– pseudo-random numbers and choices
rgbmatrix– Low-level routines for bitbanged LED matrices
rotaryio– Support for reading rotation sensors
rtc– Real Time Clock
samd– SAMD implementation settings
sdcardio– Interface to an SD card via the SPI bus
sdioio– Interface to an SD card via the SDIO bus
sharpdisplay– Support for Sharp Memory Display framebuffers
socket– TCP, UDP and RAW socket support
storage– Storage management
struct– Manipulation of c-style data
supervisor– Supervisor settings
terminalio– Displays text in a TileGrid
time– time and timing related functions
touchio– Touch related IO
uheap– Heap size analysis
ulab– Manipulate numeric data similar to numpy
usb_hid– USB Human Interface Device
usb_midi– MIDI over USB
ustack– Stack information and analysis
vectorio– Lightweight 2d shapes for displays
watchdog– Watchdog Timer
wiznet– Support for WizNet hardware, including the WizNet 5500 Ethernet adaptor.
help()– Built-in method to provide helpful information
- Supported Ports
- SAMD21 and SAMD51
- CircuitPython port to Spresense
- LiteX (FPGA)
- CircuitPython Port To The NXP i.MX RT10xx Series
- CircuitPython Port To The Nordic Semiconductor nRF52 Series
- Circuitpython on STM32
- Circuitpython on ESP32-S2
- Additional CircuitPython Libraries and Drivers on GitHub