Feather / FeatherWing Specification

Introduction

Adafruit makes Feather devices that generally have a microcontroller (MCU). They also make FeatherWings that stack on the Feather and add additional functionality such as GPS, sensor, etc. The link below to the Adafruit Feather/FeatherWing specification provides a lot of information. I will only summarize what I find most helpful, or missing.

Afafruit's Feather Specification

Pinout Reference
Feather Spec.	Feather M0 Basic	Feather M4 Express	\|	Feather Spec.	Feather M0 Basic	Feather M4 Express
RST	RST	RST	\|	---	---	---
3V3	3V3	3V3	\|	---	---	---
ARf	ARf	ARf	\|	---	---	---
GND	GND	GND	\|	---	---	---
A0	A0 D14	A0 D14	\|	Vbat	Vbat	Vbat
A1	A1 D15	A1 D15	\|	EN	EN	EN
A2	A2 D16	A2 D16	\|	Vbus	Vbus	Vbus
A3	A3 D17	A3 D17	\|	D13	D13 LED	D13 LED
A4 or D24 (2)	A4 D18	A4 D18	\|	D12	D12	D12
A5 or D25 (2)	A5 D19	A5 D19	\|	D11	D11	D11
SCK	D24 SCK	D25 SCK	\|	D10	D10	D10
MO	D23 MOSI	D24 MOSI	\|	D9	A7 D9	D9
MI	22 MISO	23 MISO	\|	D6	D6	D6
Rx D0	0	0	\|	D5	D5	D5
Tx D1	D1	D1	\|	SCL	D21 SCL	D21 SCL
(1)	GND	D4	\|	SDA	D20 SDA	D22 SDA

Color Key: SPI I2C (I2C pullup on FeatherWing, not Feather) GPIO free

(1) free pin that varies in use from one board to the next.

(2) D24 and D25 can be used in place of A4 and A5 when the pins do not feature any analog capabilities.

RST Pull to ground to reset the Feather. A tactile button to reset must be on the Feather.

The EN pin is an input to the Feather and must depower the 3.3V output. Typically connected to the Enable pin on the 3.3V regulator, with a 100K pullup. It does not disable VBAT/VUSB.

All GPIO are 3.3V logic. 7 mA per pin recommended (10 mA max).

Digital input HIGH when > 2.31 V, LOW < 0.99 V.

Input power to the Feather

USB port The USB port with at least 500 mA supply is the primary power connection. The USB port input power is regulated down to 3.3 VDC by the Feather and is available on pin '3V3'. It also charges any connected 3.7 V LiPoly battery (LiPo battery output is 4.2 V fully charged).

Vusb You may provide at least 500 mA @ 4.5 to 5.0 VDC directly to the Vusb pin, rather than using the USB port (WARNING: don't use both!). When Vusb is is supplied power, it will provide power to the device, and charge any connected LiPo battery.

3V3 pin You can provide at least 500 mA @ 3.3 VDC directly to the '3V3' pin (max 3.6 V), provided you disable the XC9258A on board regulator by connecting the 'EN' pin to ground, and then never connect power to the USB port or the LiPo connector. When you disable the on board regulator (EN to gnd), the output drops to about ~0.8 V (not 0).

Li+ pin You may provide at least 500 mA @ 3.6 to 4.2 VDC directly to the Li+ pin, rather than using the LiPo connector. This will charge the LiPo battery and provide power to the Feather. Do not disable the on board regulator XC9258A).

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