More LED's: Binary Counter

In this example we will display the binary values to LEDs connected to PORT2. P2_0 represents the least significant bit (LSB) and P2_3 represents the most significant bit (MSB).

For example, if we want to display binary count from 0(0x00) to 15(0x0F), we can hard code the values or another approach is use a variable and increment its value by 1 and display its value to PORT2.


Example 1: Hard Coded values

#include <at89x52.h>

void delay (void)
{
    unsigned int i;
     for(i=0; i<0x7FFF; i++);
}

void main (void)
{
   P2 = 0; //initially turn LEDS off

      while(1)
         {
                P2 = 0x00;
                delay();
                P2 = 0x01;
                delay();
                P2 = 0x02;
                delay();
                P2 = 0x03;
                delay();
                P2 = 0x04;
                delay();
                P2 = 0x05;
                delay();
                P2 = 0x06;
                delay();
                P2 = 0x07;
                delay();
                P2 = 0x08;
                delay();
                P2 = 0x09;
                delay();
                P2 = 0x0A;
                delay();
                P2 = 0x0B;
                delay();
                P2 = 0x0C;
                delay();
                P2 = 0x0D;
                delay();
                P2 = 0x0E;
                delay();
                P2 = 0x0F;
                delay();
         } 
}

Example 2: Improved version

#include <at89x52.h>

void delay (void)
{
    unsigned int i;
     for(i=0; i<0x7FFF; i++);

}

void main (void)
{
   unsigned char val = 0  //the value of this variable will be transferred to P2
   P2 = 0; //initially turn off all LEDs


    while(1)
       {
            P2 = val;  //transfer val to P2
                 val++; //increment val by 1
            if(val>=0x0F) //if we reach 0x0F then reset value
               val = 0;

             delay();

       }

}