Calunium with power adaptor fitted
Calunium board with 3.3V power adaptor fitted.
Note the polyfuse and onboard MCP1703 3.3V regulator have been omitted. For reliable operation at 3.3V a 12MHz crystal is used (16MHz would be outside the specifications for the ATmega1284P). The standard real-time clock, DS1307, will not operate at 3.3V and unfortunately I couldn't find a pin-compatible part capable of operating at 3.3V in a dual-inline package. In this instance it has been replaced by a DS1338 mounted on a SOIC8-DIP adaptor.