Arduino clone with real-time clock, microSD socket and radio module. The layout is designed for easy assembly and maximum compatibility with the Arduino Uno, with additional functionality being compatible with the Arduino Mega2560. The optional LM61 temperature sensor is not fitted. As this particular board is intended to be powered by a boost regulator fitted to a shield the 3.3V and 5V regulators, and power LED, have not been fitted.
Version 2 features a number of improvements: there are footprints for SOIC and DIP package real-time clocks and a 5V regulator has been added. The PCB now supports the latest Arduino shield layout, with dedicated pins for I2C and IOREF signals, and 3.3V or 5V operation is possible via a jumper. An RFM12B radio module and microSD socket have been added, both are restricted to 3.3V operation. The microcontroller can be clocked from either an external crystal or ceramic oscillator. The analogue supply is smoothed with an inductor as recommended in the Atmel datasheet.
For more information see blog.stevemarple.co.uk/2012/12/calunium-version-2.html.
Eagle PCB design files available under Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) licence, github.com/stevemarple/Calunium