This release includes a number of excellent enhancements since Alpha 3 including more reliable USB, better safe mode and Particle Mesh board support. This gets us closer to beta!

This is alpha release number 5 of 4.0.0. Alpha releases do not have the complete API from 3.x on the nRF builds and are only meant for testing. (Beta release will have the full existing API but still need work.) 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 3

• 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.
• Improved safe mode and added it to nRF52 boards. Thanks to @tannewt
  • 700 millisecond period at start up where a reset will go into safe mode. RGB status is yellow and the single status LED will blink three times.
  • The stack growing to overwrite the heap will reset into safe mode.
  • nRF boards will reset into safe mode on brownout.
• Fixes to USB. Thanks to @hathach and @tannewt.
• Documentation improvements. Thanks to @C47D, @sommersoft .
• Spanish translation updates. Thanks to @yeyeto2788, @C47D and @sabas1080 .

New Boards

• Mini SAM M4 Thanks to @bwshockley
• Electronic Cats' CatWAN Thanks to @sabas1080
• Particle Argon, Boron and Xenon Thanks to @tannewt

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.

Known Issues

None

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 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.3.
Here are all the changes since 3.1.1.

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.

Note: alpha.4 was briefly released but USB didn't work on nRF52840 so it was pulled. This release has it fixed.