Datasheet

#20 / SDA - GPIO #20, also the I2C (Wire) data pin. There's no pull up on this pin by default so when using

with I2C, you may need a 2.2K-10K pullup.

#21 / SCL - GPIO #21, also the I2C (Wire) clock pin. There's no pull up on this pin by default so when using

with I2C, you may need a 2.2K-10K pullup.

#5 - GPIO #5

#6 - GPIO #6

#9 - GPIO #9, also analog input A7. 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

#11 - GPIO #11

#12 - GPIO #12

#13 - GPIO #13 and is connected to the red LED next to the USB jack

A0 - This pin is analog input A0 but is also an analog output due to having a DAC (digital-to-analog converter).

You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output

A1 thru A5 - These are each analog input as well as digital I/O pins.

SCK/MOSI/MISO (GPIO 24/23/22)- These are the hardware SPI pins, you can use them as everyday GPIO

pins (but recommend keeping them free as they are best used for hardware SPI connections for high speed.

Micro SD Card + Green LED

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

SD card!

#4 - used as the MicroSD card CS (chip select) pin

#7 - used as the MicroSD card CD (card detect) pin. If you want to detect when a card is inserted/removed,

configure this pin as an input with a pullup. When the pin reads low (0V) then there is no card inserted. When

the pin reads high, then a card is in place. It will not tell you if the card is valid, its just a mechanical switch

#8 - This pin was also left over, so we tied it to a green LED, its next to the SD card. It might be handy to blink

this LED when writing / reading valid data or some other user-alert!

Other Pins!

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