Just in time for a weekend with PyPortal we’re releasing a new beta with fixes for USB. Check it out now on circuitpython.org!

From the GitHub release page:

We are nearing the end of the betas of 4.0.0, and hope to be issuing a release candidate soon. There are still a few issues to fix before stable. We think the API’s are now stable. Please use the latest 3.x stable release (available from the new website!) when first starting with CircuitPython. It is stable.

When you find a bug please check the current known issues and file an issue if something isn’t already known.

circuitpython.org

Downloads are now available from circuitpython.org! This site makes it much easier to select the correct file and language for your board. The downloads page is here.

4.0.0

4.0.0 is the latest major revision of CircuitPython. It features:

• extensive new support for pixel-based displays (displayio)
• a port to the Nordic nRF52840 microcontroller, including support as a BLE beacon or peripheral (bleio)
• USB MIDI support
• messages translated into multiple languages

Installation

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).

New Features, Updates, and Fixes since Beta 5

• Fixed USB HID bug which caused memory corruption that caused a wide variety of issues, including connection issues on certain platforms. Thanks to @tannewt for the fix and @jerryneedell, @mgithubreq, @uhrheber, @tboie, and @emteeoh for a number of different issues that pointed to it.
• Prevent filesystem corruption by flushing data to flash filesystem before soft reboots and regularly during normal operation. Thanks to @dhalbert for the fixes and @kevinjwalters for the issue.
• Fixed a bug in TileGrid that caused memory corruption when pixel_shader was a ColorConverter, causing backgrounds to disappear and crashes. Thanks to @dhalbert for the fix and @jerryneedell for a good test case.
• Fixed USB CDC out buffering. Thanks to @tannewt and @hathach.
• Add reversed() to all builds. Thanks @dhalbert; thanks @ladyada for the suggestion.
• frequencyio is enabled only on SAMD51 for now; not tested yet on SAMD21. Thanks @dhalbert, @sommersoft.
• On nRF boards, allow NFC pins to be used for other purposes; thanks @dhalbert; thanks @uhrheber for the issue.
• Enable nvm for all SAMD boards. Thanks @jrcutler.
• New fontio builtin module for Glyph and BuiltinFont. Thanks @tannewt.
• Improve SPI display initialization. Thanks @makermelissa.
• Add socket.recv_into. Thanks @rhwlo.
• Allow display.Palette to support more than 255 colors. Thanks @deshipu.
• Calculate bpp properly for displayio.Bitmap. Thanks @deshipu.
• Work on ugame10 and pewpew boards. Thanks @deshipu.
• Build infrastructure improvements thanks to @tannewt.
• Fix nRF internal flash write logic. Thanks @dhalbert.
• Added better CPython compatibility to more builds. Thanks @dhalbert; thanks to @Singein for the issue.
• Updated frozen libraries. Thanks @dhalbert.
• Update status RGB LED more promptly. Thanks @tannewt.

New and Updated Translations

• Added Polish as a new translation. Many thanks to @deshipu.
• Updated Spanish translations. Thanks @yeyeto2788.
• Message cleanup thanks to @deshipu.

New Boards

• uChip SAMD21 board; thanks @ITACAInnovation.

Breaking Changes from 3.x!

• ure, ujson, and uerrno renamed to re, json, and errno to reflect that they are subsets of the CPython library modules. Thanks to @dhalbert.
• busio.UART breaking changes to match PySerial. Thanks to @dhalbert.
  • busio.UART constructor timeout parameter is now in seconds instead of milliseconds.
  • UART.readinto(buf) now does not allow an optional length parameter UART.readinto(buf, len).
  • UART.write(…) no longer allows strings to be written. The bytes written must be bytes or bytearray or an array.array.
• framebuf has been removed. displayio is its replacement, and will be enhanced after 4.0 to include framebuf‘s functionality. Thanks to @tannewt.
• Improve struct compatibility with CPython by enforcing stricter types. This may break your code! Thanks to @dhalbert.

Thanks

Thank you to all who used, tested, contributed, helped out, and participated on GitHub and/or Discord:
@adafruit, @anecdata, @arofarn, @arturo182, @ATMakersBill, @barbudor, @brennen, @brentru, @bwshockley, @C47D, @CarlFK, @carlosperate, @caternuson, @CedarGroveStudios, @chalei, @charlesbunaford, @cpforbes, @CraigF, @dastels, @deshipu, @dhalbert, @dsiee, @edspark, @eighthree, @emteeoh, @furlaneto, @gcvasconcelos, @glennrub, @gpshead, @hathach, @iraytrace, @Jahor, @jasonp, @jepler, @Jay Doscher, @jerryneedell, @jimblom, @JohnPark, @JoshuaLowe1002, @juanita, @KacperLA, @kattni, @kevinjwalters, @klardotsh, @Klowner, @ladyada, @larsks, @madbodger, @maholli, @Makdaam, @MakerMelissa, @MattyT, @mchobby, @microbuilder, @MikeBarela, @Mr. Certainly, @mrmcwethy, @nickzoic, @notro, @oldcrow, @penguindustin, @PhredFL, @platipo, @Rathmore, @Retoc, @rhooper, @sabas1080, @sajattack, @sajattack, @saspa, @schmarty, @Senuros, @ShawnHymel, @siddacious, @sommersoft, @SouthernDragon, @TangoJuliett, @tannewt, @Tasm-Devil, @TG-Techie, @uhrheber, @urish, @vgoodwinv, @xpecex, @yeyeto2788, @jreese and surely more we have missed. Join us on the Discord chat to collaborate.

Documentation

Documentation is available in readthedocs.io.

Here are all the changes since 4.0.0-beta.5.
Here are all the changes since 3.1.2.

This release is based on MicroPython 1.9.4 @25ae98f. Support upstream MicroPython by purchasing a PyBoard (from Adafruit here).

Troubleshooting

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