Datasheet

A reset button will reset the entire Arduino, handy for when you want to restart the board

Middle - A level shifter keeps the SD card safe from the potentially-damaging 5V signals

from the Arduino. It will work with 3V signals as well.

We also have some extra breakouts shown above, around the breakout board area

3V - this is the 3V out of the regulator. Its a good quality 3.3V reference which you

may want to power sensors. Up to 50mA is available

SQ - this is the optional Squarewave output from the RTC. You have to send the

command to turn this on but its a way of optionally getting a precision squarewave. We

use it primarily for testing

WP - this is the Write Protect pad on the SD card, you can use this to detect if the

write-protect tab is on the card by checking this pin

CD - this is the card detect pad on the SD card. When this is connected to ground, an

SD card is inserted. We suggest using the internal pullup on an Arduino pin if you want