This TinyShield lets you add a battery-backed real-time clock (RTC) to your TinyDuino projects. This lets your project keep accurate time even through the TinyDuino being reprogrammed or power losses. It is based around the Maxim DS1339 RTC and supports counting in seconds, minutes, hours, days, date, month and year with leap-year compensation (valid up to 2100).
The RTC has two time-of-day alarms that can be set to wake up the main TinyDuino processor from sleep (very useful in long term data logging applications) and will automatically switch to using the backup battery upon power loss. The backup battery is a rechargeable Lithium coin cell which is soldered onto the TinyShield and will keep the RTC time for 2.5 years before being recharged. Trickle charging of the backup battery can be enabled using a software command.