This release includes a number of excellent enhancements since Alpha 5 including many bleio and displayio improvements.

This is the first beta build of 4.0.0. There are still issues to fix before stable and the new APIs may evolve a bit more. Please use the latest 3.x stable release 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.

4.0.0

4.0.0 is the latest major revision of CircuitPython and features support for the nRF52840 BLE chipset and translated messages.

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).

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

New Features, Updates, and Fixes since Alpha 5

• displayio improvements. Thanks to @tannewt
  • Dynamic displays are now supported.
  • 8 bit parallel display bus is now supported.
  • Shapes are now supported with displayio.Shape. (Meant to be subclassed.)
  • Hallowing display now uses board.SPI() so user can use it as well.
• bleio has been rewritten to work in conjunction with Adafruit_CircuitPython_BLE. Together they now support the standard Nordic BLE UART Service. Various kinds of advertising beacons are supported as well. Also see the new library Adafruit_CircuitPython_Bluefruit, which supports communication using the Adafruit Bluefruit LE Connect app. Thanks to @dhalbert
• Add USB Midi support. Thanks to @tannewt
• Add _pixelbuf module to speed up RGBW pixels like NeoPixel and DotStar. Thanks to @rhooper
• nrf: Add PulseIn support. Thanks to @hathach
• nrf: Remove framebuf. displayio is supported. Thanks to @jerryneedell
• atmel-samd: Fix the I2C on Grand Central M4 Express
• Improve struct compatibility with CPython by enforcing stricter types. This may break your code! Thanks to @dhalbert
• Add x support to struct unpack. Thanks to @dhalbert.
• Add .height and .width to OnDiskBitmap. Thanks to @siddacious
• Add support for subclassing native classes that take kwargs into __init__. Thanks to @tannewt
• README improvements. Thanks to @kattni
• New Bahasa Indonesia (ID) translation thanks to @chalei
• Translation updates:
  • German thanks to @Tasm-Devil
  • Spanish thanks to @yeyeto2788,
  • French thanks to @arofarn
  • Tagalog thanks to @eighthree

New Boards

• SparkFun nRF52840 Mini. Thanks to @jimblom.
• Arduino MKR Zero. Thanks to @ShawnHymel
• SparkFun SAMD21 Mini. Thanks to @ShawnHymel
• Datalore IP M4. Thanks to @TG-Techie.
• MakerDiary nRF52840 MDK USB Dongle. Thanks to @gpshead.

Breaking Changes from 3.x!

• 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.
• Improve struct compatibility with CPython by enforcing stricter types. This may break your code! Thanks to @dhalbert

Known Issues

• Some documentation in the bleio module is outdated and incorrect.
• bleio services don't seem to work properly on some newer models of iOS devices, and perhaps on some Android devices as well. iPhones 6s and before seem to work, but we have had trouble with iPhone 7. A 2018 iPad also does not work. The problems seem to be due to hardware rather than iOS versions.

Thanks

Thank you to all who used, tested, contributed, helped out, and participated on GitHub and/or Discord:
@ladyada, @dhalbert, @tannewt, @kattni, @microbuilder, @hathach, @arturo182, @nickzoic, @glennrub, @siddacious, @deshipu, @sommersoft, @jerryneedell, @brentru, @caternuson, @jepler, @urish, @sajattack, @notro, @Jahor, @Makdaam, @mrmcwethy, @jepler, @notro, @mattyt, @furlaneto, @ATMakersBill, @Klowner, @klardotsh, @C47D, @carlosperate, @platipo, @xpecex, @gcvasconcelos, @saspa, @uhrheber, @nickzoic, @sabas1080, @sajattack, @JoshuaLowe1002, @Senuros, @mchobby, @Retoc, @CedarGroveStudios, @bwshockley, @yeyeto2788, @jimblom, @rhooper, @ShawnHymel, @TG-Techie, @eighthree, @arofarn, @chalei, @vgoodwinv, @gpshead, @dsiee, @Tasm-Devil, @larsks, @CarlFK 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-alpha.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.