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Appendix e: additional routines for psd estimator
1 /* ECE420, Lab 4, Reference PN Generator Implementation (Non-Optimized) */
2 /* Matt Kleffner 08/04 */
3 /* Original by Michael Frutiger 02/24/04 */
4 /* Use governed by the Creative Commons Attribution License */
5
6 #include "lab4b.h"
7
8 extern unsigned int *iseed;
9 extern int autocorr_in[N];
10
11 /* Returns as an integer a random bit, based on the 15 lowest significant
12 bits in iseed (which is modified for the next call). */
13 int randbit()
14 {
15 int newbit;
16 /* XOR bits 15, 1 and 0 of iseed */
17 newbit = (*iseed >> 15) & 1 ^ (*iseed >> 1) & 1 ^ *iseed & 1;
18 /* Leftshift the seed and put the result of the XOR's in bit 1. */
19 *iseed=(*iseed << 1) | newbit;
20 return(newbit);
21 }
22
23 void rand_fillbuffer(void)
24 {
25 int i;
26
27 for (i = 0; i < N; ++i)
28 {
29 if (randbit()) autocorr_in[i] = 32767;
30 else autocorr_in[i] = -32767;
31 }
32 }
1 /* Simple, unoptimized IIR filter (feedback only) */
2 /* for TMS320C54X series DSPs */
3 /* Copyright September 2005 by Matt Kleffner */
4 /* under the Creative Commons Attribution License */
5
6 #include "lab4b.h"
7 #include "intrinsics.h"
8
9 /* IIR values and buffers (declared in c_fft_given_iirc.asm) */
10 #define IIR_order 4
11 extern int scale;
12 extern int coef[IIR_order];
13 extern int state[IIR_order];
14
15 /* Arrays declared in main routine */
16 extern int autocorr_in[N];
17 extern int autocorr_out[N];
18
19 /* Pointer to state buffer location */
20 extern int iirptr;
21
22 void iirfilt()
23 {
24 int i, j;
25
26 _set_fract_bit();
27 /* Filter PN input */
28 for (i = 0; i < N; ++i)
29 {
30 int sum = 0;
31 /* Calculate and sum all feedback terms except the "oldest" one */
32 for (j = 0; j < (IIR_order-1); ++j)
33 {
34 sum += _i_mul_fract_fb1_ii(coef[j],state[iirptr]);
35 /* Avoid usage of "modulo" routine */
36 iirptr++;
37 if (iirptr == IIR_order) iirptr = 0;
38 }
39 /* Calculate and sum oldest feedback term without incrementing iirptr */
40 sum += _i_mul_fract_fb1_ii(coef[IIR_order-1],state[iirptr]);
41
42 /* Calculate direct input contribution */
43 sum += _i_mul_fract_fb1_ii(scale,autocorr_in[i]);
44 autocorr_in[i] = sum;
45 state[iirptr] = autocorr_in[i];
46 }
47 _reset_fract_bit();
48 }
1 /***********************************************************/
2 /* autocorr.c */
3 /* Copyright August 2004 by Matt Kleffner */
4 /* under the Creative Commons Attribution License */
5 /* */
6 /* Simple, unoptimized autocorrelation function */
7 /* for ECE 420 (TMS320C54X series) */
8 /* */
9 /* #defines expected in lab4b.h */
10 /* L: length of data in autocorr_in buffer */
11 /* N: length of data in autocorr_out buffer */
12 /* logL: log base 2 of L (used for scaling output) */
13 /* M: Largest positive lag of autocorrelation desired */
14 /* (must be < L and < N/2) */
15 /* */
16 /* 16-bit-limited input/output (must be defined elsewhere) */
17 /* autocorr_in: buffer for input data (L pts) */
18 /* autocorr_out: buffer for output data (N pts) */
19 /* N must be >= 2*M+1 */
20 /* assumed to be full of zeros at start */
21 /* output in zero-phase form */
22 /***********************************************************/
23
24 #include "lab4b.h"
25 #include "intrinsics.h"
26
27 extern int autocorr_in[L];
28 extern int autocorr_out[N];
29
30 void autocorr(void)
31 {
32 int i,j,temp;
33
34 _set_fract_bit();
35 for(i=0;i<=M;++i)
36 {
37 long int sum=0;
38 for(j=0;j<(L-i);++j)
39 {
40 temp = _i_mul_fract_fb1_ii(autocorr_in[j],autocorr_in[j+i]);
41 sum += temp;
42 }
43 autocorr_out[i]=(int)(sum >> logL);
44 }
45 _reset_fract_bit();
46
47 /* Copy values for negative indeces at end of buffer */
48 for(i=1,j=N-1;i<=M;++i,--j)
49 { autocorr_out[j]=autocorr_out[i]; }
50 }
Read also:
OpenStax, Digital signal processing laboratory (ece 420). OpenStax CNX. Sep 27, 2006 Download for free at http://cnx.org/content/col10236/1.14
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