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From the GitHub release page:

This is CircuitPython 9.0.0-rc.1, a release candidate for 9.0.0 final. This release is believed to be stable, and is meant for testing before the final release of 9.0.0.

WARNING for nRF52 boards only: If your board has an nRF52 UF2 bootloader whose version is before 0.6.1, you will not be able to load CircuitPython 8.2.0 and later, due to increased size of the firmware. See these instructions for updating your bootloader.

Notable changes to 9.0.0 since 8.x.x

Incompatibility warnings

• New storage management. See Internal below about possible new memory errors with existing programs.
• Filesystems such as SD cards must now be mounted on an existing directory as a mount point. See Storage below.
• Incompatible change in socket behavior: Sockets must be explictly made reusable. See Networking below.
• displayio.*Display.show() has been removed. Use *Display.root_group = instead.
• I2CPeripheral is now I2CTarget.

Audio

• Add synthio.Note .loop_start and .loop_end properties.
• Add synthio.Synthesizer.note_state.
• Add I2S MCLK support on Espressif.
• Allow signed amplitude in synthio.

Built-in modules

• Add OrderedDict.move_to_end().
• Add warnings module, similar to what is in CPython.
• Add locale.getlocale().
• Add codeop.compile_command().
• Remove 8.x.x deprecations: displayio.*.show(), I2CPeripheral renamed to I2CTarget.

Graphics

• Reorganize and split displayio. 8.x.x naming structure is available in 9.x.x, but will be removed in 10.0.0.
• Add jpegio JPEG decoder support.
• Add bitmapfilter image manipulation.

Internal

• New split-heap internal dynamic storage mechanism. Some CircuitPython programs may fail with MemoryError. If you encounter programs that work in 8.x.x but get MemoryError exceptions, consider filing an issue with details.
• Merge updates from MicroPython v1.19.1, v1.20.0, and v1.21.0.
• Espressif: update to ESP-IDF v5.1.3.

Networking

• Allow specifying protocol for raw sockets.
• Add mDNS TXT record support.
• Make SD cards available over web workflow.
• Allow fetching of associated stations in access-point mode.
• Incompatible change: Require explicit socket port reuse. Use socket.setsockopt(pool.SOL_SOCKET, pool.SO_REUSEADDR, 1), as in CPython.

Python interpreter

• Use terser error messages on small builds.

Storage

• CIRCUITPY drives now mount on Android.
• Increased file capacity on CIRCUITPY drives <= 128kB.
• Incompatible change: Require filesystem mounts to be on existing directories. Create /sd in fresh filesystems to provide a mount point.

Supervisor

• Add repl.py, which runs just before the REPL starts up.

USB

• Video device (“Webcam”, UVC) support.
• HID can wake up sleeping host computer.
• Further USB host support, on i.MX and RP2040.
• Allow setting USB HID interface name.

Download from circuitpython.org

Firmware downloads are available from the downloads page on circuitpython.org. The site makes it easy to select the correct file and language for your board.

Installation

To install follow the instructions in the 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).

Documentation

Documentation is available in readthedocs.io.

Port status

CircuitPython has a number of “ports” that are the core implementations for different microcontroller families. Stability varies on a per-port basis. As of this release, these ports are consider stable (but see Known Issues below):

• atmel-samd: Microchip SAMD21, SAMx5x
• cxd56: Sony Spresense
• espressif: Espressif ESP32, ESP32-S2, ESP32-S3, ESP32-C3
• nrf: Nordic nRF52840, nRF52833
• raspberrypi: Raspberry Pi RP2040
• stm: ST STM32F4 chip family

These ports are considered alpha and will have bugs and missing functionality:

• broadcom: Raspberry Pi boards such as RPi 4, RPi Zero 2W
• litex: fomu
• mimxrt10xx: NXP i.MX RT10xxx
• silabs: Silicon Labs MG24 family
• stm: ST non-STM32F4 chip families

Changes since 9.0.0-rc.0

Fixes and enhancements

• Update frozen libraries. #9046. Thanks @dhalbert.
• Fix tlsf allocation logic. #9039. Thanks @tannewt.

Port and board-specific changes

Broadcom

Espressif

• Fix RMT clock speed on ESP32-H2. #9051. Thanks @tannewt.
• Fix _bleio.Adapter name setting. #9041. Thanks @dhalbert.
• Fix tlsf allocation logic. #9039. Thanks @tannewt.
• Fix error reporting for certain connection errors. #8888. Thanks @bill88t.

i.MX

• Don’t reset USB_HOST_POWER pin on Teensy boards that have it. #9048. Thanks @dhalbert

nRF

RP2040

• Handle multiple USB setup packets: TinyUSB fix. #9042. Thanks @hathach.
• Don’t claim PWMOut pin before validation. #9024. Thanks @dhalbert.
• Update cyw43-driver to upstream version v1.0.3. #9022. Thanks @eightycc.

SAMx

SiLabs

Spresense

STM

Individual boards

• Adafruit MatrixPortal S3: disable espcamera properly. #9043. Thanks @jerryneedell and @dhalbert.

Documentation changes

• Fix supervisor.Runtime.serial_bytes_available documentation. #9032. Thanks @RetiredWizard.

Build and infrastructure changes

Translation additions and improvements

• Thanks for translations:
  • @Sokromatrix (German)
  • @wtuemura (Portuguese – Brazil)
  • @Xfox20 (German)

New boards since 9.0.0-rc.0

• Adafruit Feather ESP32-C6 4MB Flash No PSRAM. #9018. Thanks @dhalbert.
• Waveshare RP2040-Tiny. #8796. Thanks @bill88t.

Known issues

• See https://github.com/adafruit/circuitpython/issues for other issues, including issues still to be addressed for:
  • 9.0.0
  • 9.0.x
  • 9.x.x
  • long term

Thanks

Thank you to all who used, tested, and contributed since 9.0.0-rc.0, including the contributors above, and many others on GitHub and Discord. Join us on the Discord chat to collaborate.