CircuitPython 5.1.0-rc.0 released! #CircuitPython #Python @adafruit @circuitpython

CircuitPython 5.1 release candidate zero (5.1.0 rc0) has been released! From the GitHub release page:


This is CircuitPython 5.1.0-rc0, the latest minor revision of CircuitPython, and a release candidate. If this release does not have show-stopper issues, it will be re-released as 5.1.0, the first 5.1.x stable release.

Download from

Downloads are available from! The site makes it easy to select the correct file and language for your board. The downloads page is here. Downloads are no longer available from the GitHub release pages because of the large number of files for each release.


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 and improvements since 5.0.0

  • ulab, a numpy-like fast vector module (#2583 and others). Thanks @v923z, @jepler
  • Support for “f-strings”, a more convenient way to build strings dynamically. (#2690) Thanks @klardotsh, @jepler
    • Enabled on almost all boards except those with samd21 microcontrollers.
  • mpy-cross signals certain syntax errors better (#2670). Thanks @jepler
  • nRF now properly handles unaligned disk reads (#2662). Thanks @jepler
  • New builds of unix port and mpy-cross facilitate testing (#2672). Thanks @jepler
  • STM port: add PulseOut (#2668). Thanks @hierophect
  • STM port: add PulseIn (#2697). Thanks @hierophect
  • STM port: fix some GPIO clocking issues (#2680). Thanks @hierophect
  • STM port: rename directory to reflect the scope of the port (#2699). Thanks @hierophect
  • STM port: change ST drivers submodule to match TinyUSB (#2701). Thanks @hierophect
  • Winterbloom Sol: Disable USB HID descriptor (#2681). Thanks @theacodes
  • Support importing native modules in native packages (#2657). Thanks @tannewt
  • Document proximity and sound_level in design guide (#2684). Thanks @caternuson
  • Improve argument validation in displayio (#2666). thanks @dhalbert
  • Add TG-Watch02A board (#2695). Thanks @TG-Techie
  • Add UARTLogger2 board (#2705). Thanks @nightskysk
  • Fix DotStar status LED init (#2712). Thanks @tannewt

Breaking Changes and Deprecations from 4.x

  • 5.0.0 improves our internal filesystem definitions and may overwrite your existing files so make sure to back them up before updating!
  • The bleio module has been renamed to _bleio to indicate that it is meant to be used only for writing BLE libraries, and that its API may change between CircuitPython minor versions. There are many incompatible changes in _bleio since 4.0.0. Please use the latest adafruit_ble library for end-user BLE programming.
  • The displayio refresh API has been revamped to be simpler. wait_for_frame and refresh_soon have been removed. In both 4.x and 5.x, auto refresh will automatically refresh the display so they can be removed. The new auto_refresh property and refresh() function can be used to control when the screen refreshes and at a specific rate.
  • Moved audioio.Mixer to audiomixer.Mixer, which is only available on M4 microcontrollers. Moved audioio.RawSample, and audioio.WaveFile to the new module audiocore. However, for backwards compatibility, they are still available in audioio. They will be removed from audioio in 6.0.0. Thanks @jepler.
  • Added I2C.writeto_then_readfrom(). Deprecate stop= arg which will be removed in 6.x. Use I2C.writeto_then_readfrom() instead.
  • Removed re from Circuit Playground Express Display build.
  • Removed gamepad from Circuit Playground Express Crickit build.

2 New boards since 5.0.0

  • TG-Watch02A
  • UARTLogger2

Known Issues

  • displayio operations that read from an SD card (e.g., OnDiskBitmap) will interfere with other SD card operations and can cause lockup. To work around this problem, do not read or write files on the SD while the display is updating, and vice versa.
  • See for other issues.


Thank you to all who used, tested, contributed, helped out, and participated on GitHub and/or Discord, including @dhalbert, @jepler, @hierophect, @ladyada, @TG-Techie, @theacodes, @sommersoft, @tannewt, @v923z and surely more we have missed. Join us on the Discord chat to collaborate.


Documentation is available in

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


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


Builds are no longer stored as assets on this release page, because there are too many of them. Please see the Download from section above.

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