Adafruit Feather STM32F405 Express

The Adafruit Feather STM32F405 takes the Feather family to new heights with ST’s powerful 168 MHz Cortex-M4 processor — the fastest CircuitPython board from Adafruit yet!

ST takes flight in this Feather board. The new STM32F405 Feather that we designed runs CircuitPython at a blistering 168MHz – our fastest CircuitPython board ever! We put a STEMMA QT / Qwiic port on the end, so you can really easily plug and play I2C sensors. With CircuitPython basics running on this board, it's fast to get all our drivers working, then use the built-in plotter in Mu to instantly get sensor data displaying within 3 minutes of unboxing. You can use MicroPython, CircuitPython or Arduino IDE with this board, with some caveats. This board and chipset is new, so expect rapid developments and updates! CircuitPython support is in a good spot. We have digital IO, analogue in/out, I2C, SPI, PWM, SDIO, displays, RGB matrices working so far and more on the way. Arduino is supported through STM32duino. There's no auto-reset bootloader support yet so you have to pull the BOOT0 pin high and manually reset before uploading. That said, STM32 support is fantastic, and we were able to run just about every sketch we tried. MicroPython support is very solid, but Adafruit does not provide MicroPython libraries for sensors! We tested this in Arduino STM32duino with all our FeatherWings and only the RFM69/RFM9x libraries did not work (they are very platform specific). It's an extraordinarily fast Feather, and our first foray into STM32 - very exciting!

Features

* STM32F405 Cortex M4 with FPU and 1MB Flash, 168MHz speed

* 192KB RAM total - 128 KB RAM for general usage + 64 KB program-only/cache RAM

* 3.3V logic, but almost all pins are 5V compliant!

* USB-C power and data - our first USB-C Feather!

* LiPo connector and charger

* SD socket on the bottom, connected to SDIO port

* 2 MB SPI Flash chip

* Built in NeoPixel indicator

* I2C, UART, GPIO, ADCs, DACs

* Qwiic/STEMMA-QT connector for fast I2C connectivity

* We use the built-in USB DFU bootloader to load firmware. It does not come with a UF2 bootloader.

Specifications

* Dimensions: 52.0mm x 23.0mm x 10.0mm

* Weight: 6.2g

Revision History

*

* As of October 29, 2025 The SD cardholder has changed to have 'opposite' connection polarity - so if you're using STM32SD.h in Arduino, just don't pass in the SD card detect pin. (You can always use the SD detect pin separately)

Resources

* Schematic

Package Contents

* 1x Adafruit Feather STM32F405 Express

* 2x 16-pin headers