The TinyShield Real-Time Clock lets you keep track of time in seconds, minutes, hours, days, date, month and year with leap-year compensation (valid up to 2100). This TinyShield is based around the Maxim DS1339 Real-Time clock.
The Maxim DS1339 is a very low power real-time clock, drawing only 400 nA to maintain time keeping. Due to the low power, a coin cell battery is sufficient to run this board. This TinyShield can operate over the entire TinyDuino voltage range (2.7 - 5.5V) safely.
The Real-Time Clock TinyShield uses the I2C bus to communicate between the TinyDuino processor and the Maxim DS1339 RTC. Below is a sample sketch to get set and get the time values for the RTC on the USB serial port:
Plug in your TinyDuino to your computer with the USB TinyShield and the RTC TinyShield attached.
Upload the code using Codebender directly from this webpage. Alternatively, open the Arduino IDE and copy the source code above into it, and upload to the TinyDuino.
Open up the Serial Monitor, and you'll be able to configure and read out the time values (using options 4 & 5):
This example lets you configure the RTC Alarm Function to wakeup the TinyDuino Processor to perform a function - this particular example will turn on or off an IO pin, so you can turn on an LED or use a Relay to control an external light.