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7.3 Lab 4: extension (Page 3/3)

Appendix e: additional routines for psd estimator

/* ECE420, Lab 4, Reference PN Generator Implementation (Non-Optimized) */
/* Matt Kleffner 08/04                                                  */
/* Original by Michael Frutiger 02/24/04                                */
/* Use governed by the Creative Commons Attribution License             */

#include "lab4b.h"

extern unsigned int *iseed;
extern int autocorr_in[N];

/* Returns as an integer a random bit, based on the 15 lowest significant
   bits in iseed (which is modified for the next call). */
int randbit()
{
   int newbit;
   /* XOR bits 15, 1 and 0 of iseed */
   newbit =  (*iseed >> 15) & 1 ^ (*iseed >> 1) & 1 ^ *iseed & 1;
   /* Leftshift the seed and put the result of the XOR's in bit 1. */
   *iseed=(*iseed << 1) | newbit;  
   return(newbit);
}

void rand_fillbuffer(void)
{
   int i;

   for (i = 0; i < N; ++i)
   {
      if (randbit()) autocorr_in[i] =  32767;
      else           autocorr_in[i] = -32767;
   }
}

/* Simple, unoptimized IIR filter (feedback only) */
/* for TMS320C54X series DSPs                     */
/* Copyright September 2005 by Matt Kleffner      */
/* under the Creative Commons Attribution License */
/* Works for TMS320C55X series as well			  */

#include "lab4b.h"
#include "intrinsics.h"

/* IIR values and buffers (declared in c_fft_given_iirc.asm) */
#define IIR_order 4
extern int scale;
extern int coef[IIR_order];
extern int state[IIR_order];

/* Arrays declared in main routine */
extern int autocorr_in[N];
extern int autocorr_out[N];

/* Pointer to state buffer location */
extern int iirptr;

void iirfilt()
{
    int i, j;

    _set_fract_bit();
    /* Filter PN input */
    for (i = 0; i < N; ++i)
    {
       int sum = 0;
       /* Calculate and sum all feedback terms except the "oldest" one */
       for (j = 0; j < (IIR_order-1); ++j)
       {
          sum += _i_mul_fract_fb1_ii(coef[j],state[iirptr]);
          /* Avoid usage of "modulo" routine */
          iirptr++;
          if (iirptr == IIR_order) iirptr = 0;
       }
       /* Calculate and sum oldest feedback term without incrementing iirptr */
       sum += _i_mul_fract_fb1_ii(coef[IIR_order-1],state[iirptr]);

       /* Calculate direct input contribution */
       sum += _i_mul_fract_fb1_ii(scale,autocorr_in[i]);
       autocorr_in[i] = sum;
       state[iirptr] = autocorr_in[i];
    }
    _reset_fract_bit();
}

/***********************************************************/
/* autocorr.c                                              */
/* Copyright August 2004 by Matt Kleffner                  */
/* under the Creative Commons Attribution License          */
/*                                                         */
/* Simple, unoptimized autocorrelation function            */
/* for ECE 420 (TMS320C54X series)                         */
/*                                                         */
/* #defines expected in lab4b.h                            */
/*    L: length of data in autocorr_in buffer              */
/*    N: length of data in autocorr_out buffer             */
/* logL: log base 2 of L (used for scaling output)         */
/*    M: Largest positive lag of autocorrelation desired   */
/*       (must be < L and < N/2)                           */
/*                                                         */
/* 16-bit-limited input/output (must be defined elsewhere) */
/*  autocorr_in: buffer for input data  (L pts)            */
/* autocorr_out: buffer for output data (N pts)            */
/*               N must be >= 2*M+1                        */
/*               assumed to be full of zeros at start      */
/*               output in zero-phase form                 */
/***********************************************************/
/* Works for TMS320C55X series 							   */

#include "lab4b.h"
#include "intrinsics.h"

extern int autocorr_in[L];
extern int autocorr_out[N];

void autocorr(void)
{
   int i,j,temp;

   _set_fract_bit();
   for(i=0;i<=M;++i)
   {
      long int sum=0;
      for(j=0;j<(L-i);++j)
      {
         temp = _i_mul_fract_fb1_ii(autocorr_in[j],autocorr_in[j+i]);
         sum += temp;
      }
      autocorr_out[i]=(int)(sum >> logL);
   }
   _reset_fract_bit();

   /* Copy values for negative indeces at end of buffer */
   for(i=1,j=N-1;i<=M;++i,--j)
   {  autocorr_out[j]=autocorr_out[i]; }
}

; c_fft_given_iirc.asm
; Designed for use in lab4b for ECE420



      .ARMS_off                     ;enable assembler for ARMS=0
      .CPL_on                       ;enable assembler for CPL=1
      .mmregs                       ;enable mem mapped register names

	.global _bit_rev_data
	.global _fft_data
	.global _state
	.global _scale
	.global _coef

	.copy "macro.asm"

	.sect ".data"

N	.set 1024


	.align 4*N
_bit_rev_data .space 16*2*N

	.align 4*N
_fft_data .space 16*2*N


; IIR filter
	.align 4
_coef
	.word	0
	.word	0
	.word	0
	.word	-13421

_state
	.space 16*4

_scale
	.word	19345

	.sect ".text"

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