Datasheet

#5 - GPIO #5, can also do PWM output

#6 - GPIO #6, can also do PWM output and analog input A7

#9 - GPIO #9, also analog input A9 and can do PWM output. This analog input is connected to a voltage divider

for the lipoly battery so be aware that this pin naturally 'sits' at around 2VDC due to the resistor divider

#10 - GPIO #10, also analog input A10 and can do PWM output.

#11 - GPIO #11, can do PWM output.

#12 - GPIO #12, also analog input A11

#13 - GPIO #13, can do PWM output and is connected to the red LED next to the USB jack

A0 thru A5 - These are each analog input as well as digital I/O pins.

SCK/MOSI/MISO - These are the hardware SPI pins, used by the Bluefruit LE module too! You can use them as

everyday GPIO pins if you don't activate the Bluefruit and keep the BLE CS pin high. However, we really

recommend keeping them free as they should be kept available for the Bluefruit. If they are used, make sure its

with a device that will kindly share the SPI bus! Also used to reprogram the chip with an AVR programmer if you

need.

Bluefruit LE Module + Indicator LEDs

Since not all pins can be brought out to breakouts, due to the small size of the Feather, we use these to control the

BLE module

#8 - used as the Bluefruit CS (chip select) pin

#7 - used as the Bluefruit IRQ (interrupt request) pin.

#4 - used as the Bluefruit Reset pin

Since these are not brought out there should be no risk of using them by accident!

Other Pins!

Top Side

RST - this is the Reset pin, tie to ground to manually reset the AVR, as well as launch the bootloader manually

ARef - the analog reference pin. Normally the reference voltage is the same as the chip logic voltage (3.3V) but if

you need an alternative analog reference, connect it to this pin and select the external AREF in your firmware.

Can't go higher than 3.3V!

DFU - this is the force-DFU (device firmware upgrade) pin for over-the-air updates to the Bluefruit module. You

probably don't need to use this but its available if you need to upgrade! Check out the DFU Bluefruit Upgrades

page for how to use it. Otherwise, keep it disconnected.