//Toggling PE3 to activate the optoisolator for Dragon12 Plus Trainer Board 
//PE3 of PORTE actiavtes the Base of Optoisolator (CNY75GB) on Dragon12+ board
//This program toggles PE3 to turn on and off the optoisolator. 
//The collector (COL) and emittter (EMT) pins of the Optoisolator are available to user (see bottom of the Dragon12 board).
//For Optoisolator See Chapter 15 of HCS12 book by Mazidi & Causey
//The Optoisolator used in the Dragon12 is CNY75GB. Google it to get the data sheet

//Connect +5V pin on Dragon12 to positive side of an LED (long leg)
//Connect the negative side of the LED (short leg) to COL pin of Opto on Dragon12+ board
//Connect the EMT pin of Opto (on Dragon12) to GND pin. Now by running this program the lED goes on and off.
//If you use this optoisolator to control an external device such as horn and lamp use external power as shown in chapter 15.  

#include <hidef.h>      /* common defines and macros */
#include "derivative.h"      /* derivative-specific definitions */


void MSDelay(unsigned int);
void main(void) 
{
  /* put your own code here */
  
       
    DDRE = DDRE | 0b00001000;    // PE3 as output 
     
    for (;;) 			
      {
       PORTE = PORTE | 0b00001000;     //make PE3=1 to turn on Optoislator
      MSDelay(500);         //change the delay size to see what happens
       PORTE = PORTE & 0b11110111;      //Make PE3=0 to turn off Optoisolator
      MSDelay(500);         //change delay size.

      }

}

void MSDelay(unsigned int itime)  //msec delay
  {
    unsigned int i; unsigned int j;
    for(i=0;i<itime;i++)
      for(j=0;j<4000;j++);
  }