/* 
Project activity timer (and clock) with EEPROM wear-levelling
Mark Wilson 2012
                                 +-----------------------------------+
                                 |            ARDUINO                |
                                 |                             [REF] |     
                                 |                             [GND] |           
                                 |                          LED [13] |            _ switch N/O (Green)
                                 | [RST]                        [12] +-----------+ +---<GND>
                                 | [3V3]                        [11] +---[R220]---{12}       
                       <5.0V>----+ [5V0]                        [10] +------------{11}
                       <GND>-----+ [GND]                        [ 9] +------------{10}
                                 | [GND]                        [ 8] +---[R220]---{9}
                                 | [Vin]                        [ 7] +---[R220]---{8}
                                 |                              [ 6] +------------{7}
    +------------+         {1}---+ [A0]                         [ 5] +------------{5}
    |  DS1307    |         {2}---+ [A1]                         [ 4] +---[R220]---{6}
    |      [VCC] +-<5.0V>  {3}---+ [A2]                         [ 3] +-----[Piezo]-----<GND>
    |      [GND] +-<GND>   {4}---+ [A3]                         [ 2] +-----------+ +---<GND>
    |      [SDA] +---------------+ [A4] SDA                  TX ( 1) |            - switch N/O (Red)
    |      [SCL] +---------------+ [A5] SCL                  RX ( 0) |
    +------------+               |                                   |
                                 +-----------------------------------+ 
  Where {n} is pin n on a common-anode 4-digit 7-segment display (eg LDQ-M3604RI)
*/