The datasheet for the DS3231 explains that this part is an "Extremely Accurate I²C-Integrated RTC/TCXO/Crystal". And, hey, it does exactly what it says on the tin! This Real Time Clock (RTC) is the most precise you can get in a small, low power package.

Most RTCs use an external 32kHz timing crystal that is used to keep time with low current draw. And that's all well and good, but those crystals have slight drift, particularly when the temperature changes (the temperature changes the oscillation frequency very very very slightly but it does add up!) This RTC is in a beefy package because the crystal is inside the chip! And right next to the integrated crystal is a temperature sensor. That sensor compensates for the frequency changes by adding or removing clock ticks so that the timekeeping stays on schedule.

This is the finest RTC you can get, and now we have it in a compact, breadboard-friendly breakout. With a coin cell plugged into the back, you can get years of precision timekeeping, even when main power is lost. Great for datalogging and clocks, or anything where you need to really know the time.

Comes as a fully assembled and tested breakout plus a small piece of header. You can solder header in to plug it into a breadboard, or solder wires directly.

A coin cell is required to use the battery-backup capabilities! We don't include one by default, to make shipping easier for those abroad, but you can use any CR1220 you have handy!

Check out Adafruits detailed tutorial for pinouts, assembly, wiring & testing, and more!

TECHNICAL DETAILS

Revision History:

• As of January 19, 2023 – Adafruit have updated this PCB with Adafruit Pinguin to make a lovely and legible silkscreen - you may get the new PCB or the older version with vector fonts - both are identical other than the fancy silkscreen.

Specifications

• 23mm x 17.6mm x 7.2mm / 0.9" x 0.7" x 0.28"
• Weight: 2.1g
• Datasheet, schematic, EagleCAD PCB files, and Fritzing available in the product tutorial