CircuitPython 9.1.0 Beta 4 Released!

From the GitHub release page:

This is CircuitPython 9.1.0-beta.4, a beta for CircuitPython 9.1.0, and is a new unstable release. This release has known bugs that will be addressed before 9.1.0 final.

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.


  • 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-beta.3

Fixes and enhancements

  • Correct count of available incoming serial bytes. #9400. Thanks @jepler.
  • Update frozen libraries. #9397. Thanks @dhalbert.
  • Fix OUT USB HID report handling. #9322. Thanks @dhalbert.
  • Add stream protocol support to SSLSocket. #9318. Thanks @jepler.
  • Fix file path handling errors in remote workflows. #9314, #9311. Thanks @dhalbert.
  • Fix EPaperDisplay.time_to_refresh(). #9299. Thanks @tannewt.
  • Fix espulp and support both FSM and RISCV when available. #9277. Thanks @Sola85.

Port and board-specific changes



  • Fix BLE advertising timeout and slowdown. #9395. Thanks @dhalbert.
  • Fix several BLE bugs. #9374. Thanks @dhalbert.
  • Provide a setting for maximum wifi power and adjust on several boards. #9369, #9364. Thanks @bill88t and @karlfl.
  • Prevent errors when using ping by adding a delay when necessary. #9350. Thanks @dhalbert.
  • Start BLE for workflow only when desired. #9344. Thanks @tannewt.
  • Finish BLE GATT server support. #9325. Thanks @tannewt.
  • Upgrade to ESP-IDF v5.2.2. #9325. Thanks @tannewt.
  • Enable deep sleep on all supported Espressif chips. #9324. Thanks @tannewt.
  • Support BLE pairing and bonding. #9289. Thanks @tannewt.
  • Enable _eve on Espressif boards with more than 4MB flash. #9243. Thanks @Bridgetek.



  • Fix BLE event handler garbage collection. #9285. Thanks @dhalbert.



  • Fix off-by-one errors affecting PWM frequeny. #9398. Thanks @timchinowsky.
  • Fix accuracy of ADC sample rate for analogbufio. #9396. Thanks @timchinowsky.
  • Pico W: turn off USB host and DVI support to regain RAM space. #9303. Thanks @dhalbert.


  • Fix PWM delays and rounding. #9343. Thanks @timchinowsky.




Individual boards

  • Adafruit Feather ESP32-S2 and ESP32-S3 Reverse Feathers: use correct display power pin. #9346. Thanks @lewinski.
  • Bradan Lane RP2040 Explorer Badge: reassign UART pins to IR; add frozen modules. #9389. Thanks @bradanlane.
  • Espressif ESP32-S3-DevKitM-1: Add missing pins. #9287. Thanks @fetsnleds.
  • M5Stack Cardputer improvements: #9280, #9273. Thanks @bill88t.
  • Seeed WIO Terminal: add explanatory comments in pins.c. #9371. Thanks @stonehippo.
  • Sunton ESP32 2432S028: rotate display. #9340. Thanks @occasional-contributor.

Documentation changes

  • Update espressif README. #9309. Thanks @bill88t.
  • Update AnalogIn limitations for Espressif. #9272. Thanks @dhalbert.

Build and infrastructure changes

  • Use macOS 12 for mpy-cross builds. #9388, #9329. Thanks @jepler.
  • Use Python 3.9 or higher for circuitpython_setboard. #9368. Thanks @FoamyGuy.
  • Fix custom board build available via GitHub web. #9298, #9293. Thanks @tyeth.
  • Use uncrustify from PyPi micropython-uncrustify. #9295. Thanks @dhalbert.
  • Remove unused global board_display_obj. #9294. Thanks @bablokb.
  • Generate CSV tables of board details. #9278. Thanks @timchinowsky.

Translation additions and improvements

  • Thanks for translations:
    • @andibing (English – UK)
    • @hacimuhammed (Turkish)
    • @hexthat (Chinese – Pinyin)
    • @johnnohj (English – UK, German)
    • @kerem3338 (Turkish)
    • @wtuemura (Portuguese – Brazil)
    • @Xfox20 (German)

New boards since 9.1.0-beta.3

  • 8086 USB Interposer. #9401. Thanks @burtyb
  • Adafruit Feather RP2040 Adalogger. #9290. Thanks @dhalbert.
  • ARCHI NEWSAN: #9387, #9353. Thanks @EricAlmendras.
  • Arduino Nano 33 BLE Rev2. #9347. Thanks @applecuckoo.
  • AutosportLabs ESP32-CAN-X2. #9281. Thanks @autosportlabs.
  • Espressif ESP32 TTGO T8 v1.7. #9391. Thanks @aguaviva.
  • NodeMcu ESP32-C2. #9300. Thanks @bill88t.
  • Oak Dev Tech RPGA Feather. #9292. THanks @skerr92.
  • Seeed Xiao ESP32C6. #9326. Thanks @MatthewJeffson.
  • Sunton ESP32 2432S032C with 3.2in display. #9316. Thanks @bablokb.
  • ThingPulse Pendrive S3. #9296. Thanks @squix78.
  • UnexpectedMaker FeatherS3 Neo. #9307. Thanks @UnexpectedMaker.
  • Waveshare ESP32-S3-Tiny. #9274. Thanks @kylefmohr.

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.3, including the contributors above, and many others on GitHub and Discord. Join us on the Discord chat to collaborate.

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