Precision RTC Plug

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 CR1220 3V lithium battery inserted).
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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.

Add a CR1220 3V lithium battery for continuous time keeping without power to the board.


There is no configuration required. The RTC chip on this plug responds to I2C address 0x68.

Header Pinouts

Design Info

Dimensions: 21.1 x 31.8 mm
CadSoft EAGLE design files: see below.
This plug can be operated at 5V as well as 3.3V.

This board uses the conventions of a JeePlug and can be used with the ports on a JeeNode. It can also be used with other boards and MCU’s, if you hook it up properly and adapt the interface code for it.

How to Get It


  • None

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