/**************************************************/
/*  Software control function generator           */
/*  Using the printer port                        */
/*  Free running Square wave generator            */
/*  Frequency depends on the loop value entered   */
/**************************************************/

#include<stdio.h>
#include<conio.h>
#include<dos.h>
#include<math.h>
#include<time.h>

unsigned char    inval, top, topcnt, printcontrol ;

int              loop, base, angle ;
float            maxv, minv ;

/***********************************************/
/*       Reads the input data                  */
/***********************************************/

unsigned char readport()
{
 unsigned char dummy ;

 dummy = inp(base + 2) ;
 outp((base + 2), (dummy & 0X0D)) ;
 inval = (inp(base + 1) & 0XF0) >> 4 ;
 outp((base + 2), (dummy | 0X02)) ;
 inval = (inval | inp(base + 1) & 0XF0) ^ 0X88 ;
 return inval ;
}

/***********************************************/
/*      Reads a port and prints the value      */
/***********************************************/

unsigned char readwrite()
{
 inval = readport() ;
 gotoxy(10, 17) ;
 printf("%d",inval) ;
 return inval ;
}

/*************************************************/
/*  output a test waveform                       */
/*************************************************/

void out_test()
{
 unsigned int  cnt, cntmax, cntmin, bincode ;
 unsigned char pol, inprt ;
 int           dummy, int_vout, hilo ;
 float         vout, hvout, lvout ;
 time_t t, end_t ;

 if (maxv >= 0 )
   {
    pol = 1 ;
    hvout = maxv ;
   }
  else
   {
     pol = 0 ;
     hvout = maxv * -1 ;
   }

 vout = 511.0 * (hvout / 5.0) ;
 int_vout = vout ;
 if (pol == 1) bincode = int_vout + 0X0200 ;
  else         bincode = 0X0200 - int_vout ;


 cntmax = bincode & 0X3FF ;

 if (minv >= 0 )
   {
    pol = 1 ;
    lvout = minv ;
   }
  else
   {
     pol = 0 ;
     lvout = minv * -1 ;
   }

 vout = 511.0 * (lvout / 5.0) ;
 int_vout = vout ;
 if (pol == 1) bincode = int_vout + 0X0200 ;
  else         bincode = 0X0200 - int_vout ;


 cntmin = bincode & 0X3FF ;


 for (hilo = 0 ; hilo < 2 ; ++hilo)
  {
    if (hilo == 1 ) cnt = cntmax ;
     else           cnt = cntmin ;


    inprt = cnt ;
    topcnt = cnt >> 8 ;
    topcnt = topcnt & 0X03 ;

    if (topcnt == 0X00) top = (top & 0X02) | 0X01 ;

    if (topcnt == 0X01) top = top & 0X02 ;

    if (topcnt == 0X02) top = top | 0X05 ;

    if (topcnt == 0X03) top = (top & 0X02) | 0X04 ;

    gotoxy(10, 12) ;
    printf("Hilo %4d  maxv %4.1f  minv %4.1f  ",hilo, maxv, minv) ;
    outp(base, inprt) ;
    outp(base + 2, top) ;

    t = time(NULL) ;
    end_t = t + (loop / 2) ;
    while (t < end_t)
     {
      t = time(NULL) ;
     }

/*     for (dummy = 0 ; dummy < loop ; ++dummy) delay(500) ;*/
  }
}

/*****************************************************/
/*              Main Program                         */
/*****************************************************/

int main(void)
 {
   int LPT1 = 0X378 ;
   int LPT2 = 0X278 ;
   int LPT3 = 0X3BC ;

   int dummy ;

   clrscr() ;

   base   = LPT2 ;
   top    = 0 ;
   printf ("FREE RUNNING SQUARE WAVE GENERATOR \n\n") ;

   printf ("Enter Period in seconds ") ;
   scanf("%d", &loop) ;
   fflush(stdin) ;

   printf ("Enter max Voltage ") ;
   scanf("%f", &maxv) ;
   fflush(stdin) ;

   printf ("Enter min Voltage ") ;
   scanf("%f", &minv) ;
   fflush(stdin) ;

   while (!kbhit()) out_test() ;
   return 0 ;
 }