//Connect FOUR 7-Segment Displays to 4 individual ports
//Display 9999 to 0 in loop with delay. Do not display the prefix 0

#include "register.h"
#include "functions.h"

#define LOWER_LIMIT 0
#define UPPER_LIMIT 9999

void setup()
{
  /*Display 3 is connected to PORTF.
    Display 2 is connected to PORTK.
    Display 1 is connected to PORTA.
    Display 0 is connected to PORTC.*/

  *dirf = 0xFF;//set PORT F as o/p port .
  *dirk = 0xFF;//set PORT K as o/p port .
  *dira = 0xFF;//set PORT F as o/p port .
  *dirc = 0xFF;//set PORT K as o/p port .

  int i;
  volatile long j = 0;
  int digits[5];

  while (1)
  {
    for (i = UPPER_LIMIT; i >= LOWER_LIMIT; i--)
    {
      int digits[5] = {(int)(i % 10), //ones digit
                       (int)(i  / 10) % 10, //tens degit
                       (int)(i / 100)  % 10, //hundreds digit
                       (int)(i / 1000) //thousands digit
                      };

      //prefix 0s should not be displayed

      *outc = display(digits[0]);//ones

      if (digits[3] != 0 || digits[2] != 0 || digits[1] != 0)
        *outa = display(digits[1]);//tens

      if (digits[3] != 0 || digits[2] != 0)
        *outk = display(digits[2]);//hundreds

      if (digits[3] != 0)
        *outf = display(digits[3]);//thousands

      for (j = 0; j < 150000; j++);//delay for the display
    }
  }
}