di3080.txt
;************************************************************************************************
;
; LISTING 1 - C PROGRAM FOR PC-CONFIGURABLE FILTER
;
; "PC-based configurable filter uses no digital potentiometers," EDN, January 23, 2003, pg 76
;
;************************************************************************************************

#include<dos.h>
#include<conio.h>
#include<stdio.h>
#include<process.h>
#define LPT 0x378        /* Data Port Address    */
#define CONT 0x37A       /* Control Port Address */
#define ESC 27
typedef unsigned char u08;
enum boolean {false,true};

/* Funtion Declarations */
void Chip_Program(u08);  /* To set the analog switches */
void showbits(u08);      /* To see bit pattern */
void DrLine(void);       /* Draw a Line */
void init(void);         /* Initializes the Parallel Port */

void main()
{
 int fch,ctr,qch;
 u08 pdat,tdat;
 float freq,qlty;
 init();
 do{
 clrscr();
 printf("RECONFIGURABLE UNIVERSAL FILTER  By Saurav Gupta & Tejinder Singh\n");
 DrLine();
 printf("  Select Frequency(in Hz/sec)\n");
 DrLine();
 printf("\t(1) 159 \t(6)  8110.0\n");
 printf("\t(2) 1591.5\t(7)  30.68 K\n");
 printf("\t(3) 1750.7\t(8)  32.20 K\n");
 printf("\t(4) 6366.0\t(9)  37.00 K\n");
 printf("\t(5) 7957.0\t(10) 38.70 K\n");
 DrLine();
 printf("Your Choice :");
 scanf("%d",&fch);
 }while(fch<1 || fch>10); /* Loop until a valid choice is entered*/

  switch(fch)
 {
  case 1 : freq=159; pdat=0x08; break;
  case 2 : freq=1591.5; pdat=0x04; break;
  case 3 : freq=1750.7; pdat=0x0C; break;
  case 4 : freq=6366; pdat=0x02; break;
  case 5 : freq=7957; pdat=0x06; break;
  case 6 : freq=8110; pdat=0x0E; break;
  case 7 : freq=30680; pdat=0x01; break;
  case 8 : freq=32200; pdat=0x05; break;
  case 9 : freq=37000; pdat=0x03; break;
  case 10: freq=38000; pdat=0x0F; break;
 }


 do{
 clrscr();
 printf("Filter with Reconfigurable Characteristics\n");
 DrLine();
 printf("   Select Q (The Quality Factor)\n");
 DrLine();
 printf("\t(1) 2.24\t(9)  4.70\n");
 printf("\t(2) 2.50\t(10)  5.36\n");
 printf("\t(3) 2.35\t(11)  6.00\n");
 printf("\t(4) 2.65\t(12)  6.38\n");
 printf("\t(5) 2.90\t(13) 7.72\n");
 printf("\t(6) 3.12\t(14) 11.01\n");
 printf("\t(7) 3.40\t(15) 33.72\n");
 printf("\t(8) 3.72\n");
 DrLine();
 printf("Your Choice :");
 scanf("%d",&qch);

 }while(qch<1 || qch>15);
  switch(qch)
 {
  case 1 : qlty=2.24; tdat=0xF0; break;
  case 2 : qlty=2.50; tdat=0xB0; break;
  case 3 : qlty=2.35; tdat=0x70; break;
  case 4 : qlty=2.65; tdat=0x30; break;
  case 5 : qlty=2.90; tdat=0xD0; break;
  case 6 : qlty=3.12; tdat=0x50; break;
  case 7 : qlty=3.40; tdat=0x90; break;
  case 8 : qlty=3.72; tdat=0x10; break;
  case 9 : qlty=4.70; tdat=0xE0; break;
  case 10: qlty=5.36; tdat=0x60; break;
  case 11: qlty=6.00; tdat=0x40; break;
  case 12: qlty=6.38; tdat=0xA0; break;
  case 13: qlty=7.72; tdat=0x20; break;
  case 14: qlty=11.01; tdat=0xC0; break;
  case 15: qlty=33.72; tdat=0x80; break;
 }
 pdat=pdat|tdat;
 printf("\nYou Have Selected the Filter with\n");
 printf("Frequency : %6.2f Hz/sec\nQuality Factor : %3.2f\n",freq,qlty);
 printf("Bit Pattern : ");
 showbits(pdat);
 printf("\n");
 DrLine();
 printf("\nPress \nEnter : To Set the Switches\nEsc   : To Exit");
 if(getch()==ESC)
 exit(0);
 Chip_Program(pdat);
 printf("\n");
 DrLine();
 printf("Chip Programmed Successfully!!\nPress any key to exit");
 getch();
}

void DrLine(void)
{
 int ctr;
 for(ctr=0;ctr<50;ctr++)
  printf("%c",205);
  printf("\n");
}

void init(void)
{
 outport(CONT,0xFF);
 delay(100);
 outport(LPT,0x00);
 delay(100);
}

void Chip_Program(u08 pdat)
{
 outport(CONT,0x00);
 delay(200);
 outport(LPT,pdat);
 delay(200);
 outport(CONT,0xFF);
 delay(200);
}

void showbits(u08 num)
{
 int i,k,mask;
 printf("%x (Hex),\t\t",num);
 for(i=7;i>=0;i--)
 {
  if(i==3 || i==7 || i==11)
  printf(" ");
  mask=0x0001<<i;
  k=num & mask;
  k==0 ? printf("0"):printf("1");
 }
 printf(" (Binary)");

}