CircuitPython 9.1.0 Released!

From the GitHub release page:

This is CircuitPython 9.1.0, the latest minor revision of CircuitPython, and is a new stable release.

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 since 9.0.0

Incompatibility warnings

  • API changes to floppyio.
  • String values in settings.toml must be quoted.


  • RP2040 I2SOut supports BLCK and LRCLK in either order.
  • ESP32-S3 supports audiomp3.
  • audiomp3 supports streaming from HTTP servers.


  • BLE GATT server support on Espressif.
  • Pairing and bonding support on Espressif.

Built-in modules

  • Enhance collections.deque functionality.
  • Add keypad_demux.DemuxKeyMatrix: use multiplexer for one side of a keypad matrix.
  • Add integration-based debouncing to keypad.
  • supervisor.Runtime.serial_bytes_available now returns a count instead of a bool.
  • Incompatible change: floppyio improvements, including API changes.
  • Espressif: microcontroller.cpu.frequency is settable.


  • fourwire.FourWire: chip_select pin is now optional.
  • picodvi now supports 640×240 and 800×240 resolutions.
  • Enable _eve on Espressif boards with more than 4MB flash.


  • Espressif: update to ESP-IDF v5.2.2.
  • Espressif: Change task-switching quantum to 1 millisecond from 10 milliseconds.


  • Implement ssl module for anything that provides socket.
  • Add stream protocol support to SSLSocket.


  • New port for renode hardware simulator.


  • Enable deep sleep on all supported Espressif chips.


  • String values in settings.toml must be quoted.


  • max3421e USB host support.
  • Allow user-specified names for usb_midi interfaces and jacks.

Download from

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


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 is available in

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-C2, ESP32-C3, ESP32-C6
  • nordic: 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
  • renode: hardware simulator
  • silabs: Silicon Labs MG24 family
  • stm: ST non-STM32F4 chip families

Changes since 9.1.0-rc.0

This release is a relabeling of 9.1.0-rc.0 and is otherwise identical to that release.

Known issues

  • See for other issues, including issues still to be addressed for:


Thank you to all who used, tested, and contributed since 9.1.0-beta.4, including the contributors above, and many others on GitHub and Discord. Join us on the Discord chat to collaborate.

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