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The Precision RTC Plug is a small (21x35mm) board containing a low power real-time clock with battery backup. It continues to track the time with second by second resolution while the attached node is sleeping or even powered off (with optional battery inserted).

An I2C bus running at 3.3V is used as interconnect, with all the power and signal lines brought out to to both sides of the board to allow daisy-chaining with other I2C-conformant boards.

The support library is the same as for the lower specification RTC plug. This board achieves an order of magnitude better apparent drift error by  internal compensation techniques that automatically adjust for temperature changes and crystal ageing.

The pre-assembled version comes with the SMD-sized DS3231 chip, crystal, battery holder, and decoupling capacitor already soldered onto the board. There is a 6-pin male plug header to solder with the orientation you want but note that No CR1220 coin cell battery is included.

The PCB only variant contains just the board for the Precision RTC Plug. No parts, no headers, no battery.

Add a 3 V Coin Cell Lithium Battery for continuous time keeping without power to the board.

As connectors you can use a Plug Headers set with 10 male and 10 female 6-pin headers, which makes it easy to connect multiple plugs and JeeNodes in a “standard” way. Or you can solder the board directly in place for more permanent use.

The documentation and full design details are freely available.

This board announced in this Weblog, documentation is under revision now