Datasheet

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

To the right of the SD card holder:

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

SD card is inserted. It is open-drain, use a pullup (either physical resistor or enabled

in software)

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. It is open-drain, use a pullup

(either physical resistor or enabled in software)

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. The output is open drain so a pullup (either physical

resistor or enabled in software)

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