====== Adafruit 7 Segment Clock Type Display ======
The Adafruit 7 segment clock display provides a four digit display with colons with an ''i2c'' interface. It is used by including the ''Wire.h'', ''Adafruit_LEDBackpack.h'' and ''Adafruit_GFX.h'' libraries.
===== Library Functions =====
=== digit ====
Digits 0 and 1 are the left had pair if the display, digit 2 is the colon collection and digits 3 qnd 4 are the right hand pair.
==== .clear() ====
This clears the display buffer. Don't forget to call .writeDisplay() subsequently to update the display from the display buffer.
==== .writeDigitNum(digit, value) ====
This writes the value to the digit position specified on the display. The value can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, b, C, d, E and F. Values outside this range are displayed as spurious symbols. **CHECK THIS**
==== .writeDigitRaw(digit, bitmask) ====
The bitmask for normal digits is assembled by adding the values of the segments you want to effect thus...

           __1__
          |     |
          32    2
          |     |
           __64_ 
          |     |
          16    4
          |     |
           __8__   . 128

E.g. to display the letter S the bitmask should be 1 + 4 + 8 + 32 + 64 = 109 so the call to the function should be ''.writeDigitRaw(digit, 109);''
==== .writeDisplay() ====
This updates the physical display from the display buffer. It must be called after chaging the contents of the display buffer before any changes can be seen.