Adafruit Launches STM32F405 Feather Express, Its Fastest CircuitPython Dev Board Yet

STMicro STM32F405 running at 168MHz in a Feather form factor makes for a very quick CircuitPython board, Adafruit boasts.

Gareth Halfacree
a month ago β€’ Hardware 101

Adafruit has begun sales of its fastest CircuitPython-compatible development board yet, the Adafruit STM32F405 Feather Express which runs the popular programming environment at 168MHz.

Unveiled earlier this month and now on sale both through Adafruit itself and its international reseller community, the Adafruit STM32F405 Feather Express takes the breadboard-friendly Feather form factor and adds an STMicroelectronics STM32F405 32-bit Arm Cortex-M4 processor running at 168MHz, 1MB of flash memory, a 2MB SPI flash module, on-board NeoPixel indicator, and a Qwiiic/STEMMA-QT compatible connector for solderless hardware interfacing over I2C.

The Feather board breaks out the STM32F405's various pins, including I2C, UART, analogue-to-digital converters (ADCs), digital-to-analogue converters (DACs), and general-purpose input/output (GPIO), all of which use 3.3V logic but are 5V-safe. In another departure from the norm, the board also uses USB Type-C for data and power β€” making it the first Adafruit Feather board to make the switch - while a microSD socket with SDIO compatibility is included at the bottom as well as a connector and integrated charging circuitry for an optional lithium-polymer battery.

There are a handful of caveats to use of the new board, however. The CircuitPython port is under active development, and cannot yet support DisplayIO or SDIO SD cards; the board can be programmed using the Arduino IDE, but lacks an auto-reset bootloader necessitating manual boot-mode toggling and resetting; and while the board boasts "very solid" MicroPython support, Adafruit doesn't provide compatible sensor libraries.

Hardware compatibility with Adafruit's FeatherWings add-ons, meanwhile, is claimed to be good β€” only the RFM69/RFM9x libraries failed to operate.

More information on the board can be found on Adafruit's learning portal.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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