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.
We've had a breakout board version of this RTC for a while, but Adafruit want to make it even easier for folks to use, so now it comes with STEMMA QT connectors for plug-and-play simplicity.
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 data-logging and clocks, or anything where you need to really know the time. 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.
To make life easier so you can focus on your important work, Adafruit have taken the sensor and put it onto a breakout PCB along with support circuitry to let you use it with 3.3V (Feather/Raspberry Pi) or 5V (Arduino/ Metro328) logic levels. Additionally, since it speaks I2C you can easily connect it up with two wires (plus power and ground!). They've even included SparkFun qwiic compatible STEMMA QT connectors for the I2C bus so you don't even need to solder! QT Cable is not included, but we have a variety in the shop. Just wire up to your favorite micro and you can use the CircuitPython/Python or Arduino drivers to easily interface with the DS3231.
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.
Check out this detailed tutorial for pinouts, assembly, wiring & code for both Arduino and CircuitPython, and more!
As of January 9, 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. Additionally, this RTC breakout may come with black or tan STEMMA QT connectors. They work the same!
Datasheet, schematic, EagleCAD PCB files, and Fritzing available in the product tutorial
Product Dimensions: 25.4mm x 17.8mm x 7.8mm / 1.0" x 0.7" x 0.3"
Product Weight: 2.5g / 0.1oz