Adafruit Feather STM32F405 Express

Feather-format STM32F405 Cortex-M4 board at 168 MHz with 1 MB flash, 192 KB RAM, 2 MB SPI flash, SD socket (SDIO), STEMMA QT, USB-C, and LiPo charger. Uses DFU bootloader instead of UF2; Arduino IDE setup requires manual BOOT0 steps.

Logical pinout · physical placement not verified

GND
Common ground for all power and logic on the Feather STM32F405 Express board.
Type · GroundVoltage · 0V reference; source states common ground for power and logic.
BAT
Positive voltage to/from the JST jack for the optional LiPoly battery.
Type · PowerVoltage · Battery input/output; exact battery voltage not restated on pinouts page.
USB
Positive voltage to/from the USB-C jack when connected.
Type · USBVoltage · USB bus voltage; source identifies it as the USB-C positive voltage.
EN
3.3V regulator enable pin; pulled up, connect to ground to disable the 3.3V regulator.
Type · ControlVoltage · 3.3V regulator enable control; pulled up per source.
3V
Output from the 3.3V regulator for board/peripheral power.
Type · PowerVoltage · 3.3V output, source states it can supply 500mA peak.
RXGPIO 0PB11
UART receive pin for Serial3; also general-purpose 3.3V logic I/O.
Type · GPIO, UARTVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
TXGPIO 1PB10
UART transmit pin for Serial3; also general-purpose 3.3V logic I/O.
Type · GPIO, UARTVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
SDAGPIO 14PB7
I2C Wire data pin with 10K pull-up to 3.3V; hardware I2C1.
Type · GPIO, I2CVoltage · 3.3V pull-up on SDA per source.
SCLGPIO 15PB6
I2C Wire clock pin with 10K pull-up to 3.3V; hardware I2C1.
Type · GPIO, I2CVoltage · 3.3V pull-up on SCL per source.
SCKGPIO 23
Main SPI bus clock pin, hardware SPI2.
Type · GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MISOGPIO 24
Main SPI bus input data pin, hardware SPI2.
Type · GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MOSIGPIO 25
Main SPI bus output data pin, hardware SPI2.
Type · GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
A0GPIO 16PA4
Analogue input and DAC OUT1 true analogue output.
Type · GPIO, AnalogVoltage · Analogue output can be set from 0V to 3.3V per source.
A1GPIO 17PA5
Analogue input and DAC OUT2 true analogue output.
Type · GPIO, AnalogVoltage · Analogue output can be set from 0V to 3.3V per source.
A2GPIO 18PA6
Analogue input; alternate use SPI1 SCK.
Type · GPIO, AnalogVoltage · 3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
A3GPIO 19PA7
Analogue input; alternate use SPI1 MISO.
Type · GPIO, AnalogVoltage · 3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
STEMMA QTQwiic 3.3V
JST SH STEMMA QT/Qwiic connector power rail.
Type · PowerVoltage · 3.3V on STEMMA QT/Qwiic connector per source.
STEMMA QTQwiic GND
JST SH STEMMA QT/Qwiic connector ground.
Type · GroundVoltage · 0V reference.
STEMMA QTQwiic SDA
STEMMA QT/Qwiic connector I2C data, usable as board.SDA.
Type · I2CVoltage · 3.3V I2C connector rail per source.
STEMMA QTQwiic SCL
STEMMA QT/Qwiic connector I2C clock, usable as board.SCL.
Type · I2CVoltage · 3.3V I2C connector rail per source.
NeoPixelGPIO 8
On-board single NeoPixel data connection, Arduino pin #8 / board.NEOPIXEL.
Type · GPIOVoltage · NeoPixel powered by the 3.3V supply per source.

Pin	Type	Function	Voltage
GND	Ground	Common ground for all power and logic on the Feather STM32F405 Express board.	0V reference; source states common ground for power and logic.
BAT	Power	Positive voltage to/from the JST jack for the optional LiPoly battery.	Battery input/output; exact battery voltage not restated on pinouts page.
USB	USB	Positive voltage to/from the USB-C jack when connected.	USB bus voltage; source identifies it as the USB-C positive voltage.
EN	Control	3.3V regulator enable pin; pulled up, connect to ground to disable the 3.3V regulator.	3.3V regulator enable control; pulled up per source.
3V	Power	Output from the 3.3V regulator for board/peripheral power.	3.3V output, source states it can supply 500mA peak.
RXGPIO 0PB11	GPIO, UART	UART receive pin for Serial3; also general-purpose 3.3V logic I/O.	3.3V logic; source notes nearly all GPIO pins are 5V compliant.
TXGPIO 1PB10	GPIO, UART	UART transmit pin for Serial3; also general-purpose 3.3V logic I/O.	3.3V logic; source notes nearly all GPIO pins are 5V compliant.
SDAGPIO 14PB7	GPIO, I2C	I2C Wire data pin with 10K pull-up to 3.3V; hardware I2C1.	3.3V pull-up on SDA per source.
SCLGPIO 15PB6	GPIO, I2C	I2C Wire clock pin with 10K pull-up to 3.3V; hardware I2C1.	3.3V pull-up on SCL per source.
SCKGPIO 23	GPIO, SPI	Main SPI bus clock pin, hardware SPI2.	3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MISOGPIO 24	GPIO, SPI	Main SPI bus input data pin, hardware SPI2.	3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MOSIGPIO 25	GPIO, SPI	Main SPI bus output data pin, hardware SPI2.	3.3V logic; source notes nearly all GPIO pins are 5V compliant.
A0GPIO 16PA4	GPIO, Analog	Analogue input and DAC OUT1 true analogue output.	Analogue output can be set from 0V to 3.3V per source.
A1GPIO 17PA5	GPIO, Analog	Analogue input and DAC OUT2 true analogue output.	Analogue output can be set from 0V to 3.3V per source.
A2GPIO 18PA6	GPIO, Analog	Analogue input; alternate use SPI1 SCK.	3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
A3GPIO 19PA7	GPIO, Analog	Analogue input; alternate use SPI1 MISO.	3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
STEMMA QTQwiic 3.3V	Power	JST SH STEMMA QT/Qwiic connector power rail.	3.3V on STEMMA QT/Qwiic connector per source.
STEMMA QTQwiic GND	Ground	JST SH STEMMA QT/Qwiic connector ground.	0V reference.
STEMMA QTQwiic SDA	I2C	STEMMA QT/Qwiic connector I2C data, usable as board.SDA.	3.3V I2C connector rail per source.
STEMMA QTQwiic SCL	I2C	STEMMA QT/Qwiic connector I2C clock, usable as board.SCL.	3.3V I2C connector rail per source.
NeoPixelGPIO 8	GPIO	On-board single NeoPixel data connection, Arduino pin #8 / board.NEOPIXEL.	NeoPixel powered by the 3.3V supply per source.

Logical pinout · physical placement not verified

Pin details

21 connections

GND
Common ground for all power and logic on the Feather STM32F405 Express board.
GroundVoltage · 0V reference; source states common ground for power and logic.
BAT
Positive voltage to/from the JST jack for the optional LiPoly battery.
PowerVoltage · Battery input/output; exact battery voltage not restated on pinouts page.
USB
Positive voltage to/from the USB-C jack when connected.
USBVoltage · USB bus voltage; source identifies it as the USB-C positive voltage.
EN
3.3V regulator enable pin; pulled up, connect to ground to disable the 3.3V regulator.
ControlVoltage · 3.3V regulator enable control; pulled up per source.
3V
Output from the 3.3V regulator for board/peripheral power.
PowerVoltage · 3.3V output, source states it can supply 500mA peak.
RXGPIO 0PB11
UART receive pin for Serial3; also general-purpose 3.3V logic I/O.
GPIO, UARTVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
TXGPIO 1PB10
UART transmit pin for Serial3; also general-purpose 3.3V logic I/O.
GPIO, UARTVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
SDAGPIO 14PB7
I2C Wire data pin with 10K pull-up to 3.3V; hardware I2C1.
GPIO, I2CVoltage · 3.3V pull-up on SDA per source.
SCLGPIO 15PB6
I2C Wire clock pin with 10K pull-up to 3.3V; hardware I2C1.
GPIO, I2CVoltage · 3.3V pull-up on SCL per source.
SCKGPIO 23
Main SPI bus clock pin, hardware SPI2.
GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MISOGPIO 24
Main SPI bus input data pin, hardware SPI2.
GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
MOSIGPIO 25
Main SPI bus output data pin, hardware SPI2.
GPIO, SPIVoltage · 3.3V logic; source notes nearly all GPIO pins are 5V compliant.
A0GPIO 16PA4
Analogue input and DAC OUT1 true analogue output.
GPIO, AnalogVoltage · Analogue output can be set from 0V to 3.3V per source.
A1GPIO 17PA5
Analogue input and DAC OUT2 true analogue output.
GPIO, AnalogVoltage · Analogue output can be set from 0V to 3.3V per source.
A2GPIO 18PA6
Analogue input; alternate use SPI1 SCK.
GPIO, AnalogVoltage · 3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
A3GPIO 19PA7
Analogue input; alternate use SPI1 MISO.
GPIO, AnalogVoltage · 3.3V analogue/GPIO domain; source notes general GPIO logic is 3.3V.
STEMMA QTQwiic 3.3V
JST SH STEMMA QT/Qwiic connector power rail.
PowerVoltage · 3.3V on STEMMA QT/Qwiic connector per source.
STEMMA QTQwiic GND
JST SH STEMMA QT/Qwiic connector ground.
GroundVoltage · 0V reference.
STEMMA QTQwiic SDA
STEMMA QT/Qwiic connector I2C data, usable as board.SDA.
I2CVoltage · 3.3V I2C connector rail per source.
STEMMA QTQwiic SCL
STEMMA QT/Qwiic connector I2C clock, usable as board.SCL.
I2CVoltage · 3.3V I2C connector rail per source.
NeoPixelGPIO 8
On-board single NeoPixel data connection, Arduino pin #8 / board.NEOPIXEL.
GPIOVoltage · NeoPixel powered by the 3.3V supply per source.

Start wiring

USB · 3.3 V

Confirm the data interface matches your host board.

Module pins: BAT, USB, 3V, STEMMA QT / Qwiic 3.3V, GND, STEMMA QT / Qwiic GND, SDA / GPIO 14 / PB7, SCL / GPIO 15 / PB6. Schematik maps them to your board in the app.

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