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@dhalbert dhalbert released this Jan 7, 2019 · 2201 commits to master since this release

Changes since 3.1.1

  • All frozen libraries have been updated to their latest versions as of 2019-01-05.
  • Added runtime.serial_bytes_available. Returns True if any bytes are available to read on the USB serial input. Allows for polling to see whether to call the built-in input() or wait. (read-only). Thanks to @ATMakersBill.
  • nRF52840-related builds were removed from 3.x as of 3.1.2 because certain software downloads that 3.x depends on were removed from Nordic's website. It is no longer possible to build these on the 3.x branch. But see the 4.0 (master) branch for viable and better support for nRF52840. Note also that nRF52832 builds from commits before 3.1.2 will no longer build due to changed download locations on the Nordic website. Thanks to @dhalbert.


To install follow the instructions in our new Welcome to CircuitPython! guide. To install the latest libraries, see this page in that guide.

Try the latest version of the Mu editor for creating and editing your CircuitPython programs and for easy access to the CircuitPython serial connection (the REPL).

All builds are available as both UF2 and bin files here along with test builds.


Documentation is available on

Here are all the changes since 3.1.1.

This release is based on MicroPython 1.9.3. Support upstream MicroPython by purchasing a PyBoard (from Adafruit here).


Pre-built mpy-cross executables are available above for MacOS, Windows, Ubuntu, and Raspbian. For MacOS, Ubuntu, and Raspbian, you must make the mpy-cross download executable by doing. Then you can compile a .py file to .mpy:

$ chmod +x mpy-cross-whatever-you-downloaded         # you only need to do this once
$ ./mpy-cross-whatever-you-downloaded    # this will generate yourfile.mpy


Check out this guide for info on common problems with CircuitPython. If you are still having trouble, then post to the Adafruit Support Forums and join Discord.

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