Datasheet

Pinouts

Power Pins:

Vin - this is the power pin. Since the RTC can be powered from 2.3V to 5.5V power, you do not need a regulator

or level shifter for 3.3V or 5V logic/power. To power the board, give it the same power as the logic level of your

microcontroller - e.g. for a 5V micro like Arduino, use 5V

GND - common ground for power and logic

I2C Logic pins:

SCL - I2C clock pin, connect to your microcontrollers I2C clock line. This pin has a 10K pullup resistor to Vin

SDA - I2C data pin, connect to your microcontrollers I2C data line. This pin has a 10K pullup resistor to Vin

Other Pins:

BAT - this is the same connection as the positive pad of the battery. You can use this if you want to power

something else from the coin cell, or provide battery backup from a different separate batery. VBat can be

between 2.3V and 5.5V and the DS3231 will switch over when main Vin power is lost

32K - 32KHz oscillator output. Open drain, you need to attach a pullup to read this signal from a microcontroller

SQW - optional square wave or interrupt output. Open drain, you need to attach a pullup to read this signal from

a microcontroller pin

RST - This one is a little different than most RST pins, rather than being just an input, it is designed to be used to

reset an external device or indicate when main power is lost. Open drain, but has an internal 50K pullup. The

pullup keeps this pin voltage high as long as Vin is present. When Vin drops and the chip switches to battery

backup, the pin goes low.