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 theMaxim DS1339 RTCand 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.

Specifications:

Ultra compact size and weight (smaller than a US Quarter!)
- Square Version: 20mm x 20mm (.787 inches x .787 inches)
- Max Height (from lower bottom TinyShield Connector to upper top TinyShield Connector): 7.81mm (0.307 inches)
Maxim DS1339 Real-Time Clock (RTC)
- Real-Time Clock (RTC) Counts Seconds, Minutes, Hours, Day, Date, Month, and Year with Leap-Year Compensation Valid Up to 2100
- Two Time-of-Day Alarms
- Oscillator Stop Flag
- Automatic Power-Fail Detect and Switch Circuitry
- Backup battery trickle charge (software controlled)
I2C Mode used
- Arduino pins A4 and A5 are used by this shield
Power
- 11mAh rechargeable Lithium 3.0V battery Provides 2.5 years of timekeeping backup
- Backup battery trickle charging under software control
- TinyShield will work across the entire TinyDuino voltage range of 2.7 - 5.5V.