// *********dftest.c ***************

// FIR digital filer example

// y(n) = (x(n) + x(n-K))/2

// ICC12 compiler generates efficient code for K = 3,7,15,31 etc

// Last modified 12/15/02 by Jonathan W. Valvano

 

// Copyright 2003 by Jonathan W. Valvano, valvano@uts.cc.utexas.edu 

//    You may use, edit, run or distribute this file 

//    as long as the above copyright notice remains 



#include "HC12.h"

#include "SCI12.H"

#define K 3

#define N (K+1)

int Xdata[N];    // MACQ

unsigned int n;  // index into MACQ

#define x(m) Xdata[(n+m)%N]

   

//******** msecwait *************** 

// wait for a variable amount of time

// uses output compare 5

void msecwait(unsigned int msec){ unsigned int i,j;

  for(i=0; i<msec; i++){

    TC5 = TCNT+2000;  // 1ms wait

    TFLG1 = 0x20;     // clear C5F

    while((TFLG1&0x20)==0){};

  }

}



//******** InitFilter *************** 

// initialize Timer, disable COP, clear MACQ

void InitFilter(void){int i;

  n=0;

  for(i=0;i<=K;i++){

    Xdata[i]=0;

  }

  COPCTL = 0x00;    // disable COP 

  DDRT |= 0x40;     // PortT bit 6 is output to LED

  TSCR = 0x80;      // TEN(enable)

  TIOS |= 0x20;     // enable OC5

}



//******** Filter ***************

// implement FIR y(n) = (x(n) + x(n-K))/2

int Filter(int data){ int y;

  if(n==0){  // update index into MACQ

    n = K;  

  }

  else{

    n--;

  }

  Xdata[n] = data;

  y = (x(0)+x(K))>>1;  

  return y;

}



void main(void){ int in,out;

  InitFilter();     // initialize Filter, COP, Port T 

  SCI_Init(13);

  SCI_OutString("Adapt812 Digital Filer test 12/15/02 -JWV"); SCI_OutChar(CR);

  SCI_OutString("x(n) y(n)"); SCI_OutChar(CR);

  while(1){

    for(in=10; in<=90; in=in+5) { // simulated triangle wave data

      PORTT ^= 0x40;   // toggle LED, for debugging

      SCI_OutUDec(in);     

      SCI_OutChar(SP);

      out = Filter(in);    

      SCI_OutUDec(out);     

      SCI_OutChar(CR);

      msecwait(2000);

    }

    for(in=85; in>10; in=in-5) { // simulated data

      PORTT ^= 0x40;   // toggle LED

      SCI_OutUDec(in);

      out = Filter(in);   

      SCI_OutChar(SP); 

      SCI_OutUDec(out);     

      SCI_OutChar(CR);

      msecwait(2000);

 	}

  }

}



extern void _start();	

#pragma abs_address:0xfffe

void (*reset_vector[])() = { _start };

#pragma end_abs_address



#include "SCI12.C"