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We provide for you in Appendix
D and
E a complete C implementation
of a PSD estimator. The input is an IIR-filtered pseudo-noise (PN)sequence generator and the PSD estimate is based on windowing the
autocorrelation with a rectangular window.The code consists of the files
lab4b.c ,
lab4b.h ,
intrinsics.h ,
pn.c ,
iirfilt.c ,
autocorr.c ,
c_fft_given_iirc.asm , and the previously-given TI FFT
routine. The assembly file
c_fft_given_iirc.asm differs
from
c_fft_given.asm in that the window array has been
removed and variables and arrays associated with IIR filtering havebeen added. Note that the multiply functions in the functions are
actually compiler directives contained in
intrinsics.h .
Make sure you know which ones are used and why; note that
VPO is not defined by the TI compiler, therefore the
corresponding section of the
#ifdef statement is not used.
Open up the lab4b.pjt project and
Rebuild All .
Load
lab4b.out onto the DSP and
run the code. Make sure that anIIR-filtered PN sequence appears on channel 1 and its PSD estimate
appears on channel 2.
Does the output match your expectations based on the theory? Does this application illustrate any limitations of the FFT implementation?(Hint: note that most of the values in the FFT input are zero.) The previously-given C implementation uses a similar algorithm as theTI FFT; take a look at the C code for help. What are the limitation(s) of the FFT that show up in this application?
In
lab4b.h
M sets the number of
autocorrelation points that are calculated. What is the maximum valueof
M that allows the reference routines to run in real
time? In determining this value you may find it useful to connect awave-function generator to the input and copy input on that channel
into channel 1 of output. You may limit
M to
powers of
2 minus
1 .
1 #define N 1024 /* Length of output buffers */
2 #define L N /* Length of input data */
3 #define logL 10 /* log base 2 of L */
4 #define M 31 /* Compute 2*M+1 autocorrelation points */
5
6 /* #define M (L/2-1) */ /* Be sure to use ()'s in this case */
7 /* or algebraic substitution bugs */
8 /* can be introduced */
/* Compiler intrinsics for the TI compiler */
/* and the Very Portable Optimizer (VPO) port */
/* to TMS320C54X series DSPs */
/* */
/* Use compile option -DVPO when using VPO */
/* */
/* Copyright September 2005 by Matt Kleffner */
/* under the Creative Commons Attribution License */
/* Works with TMS320C55X series */
#ifndef INTRINSICS_H
#define INTRINSICS_H
#ifdef VPO
long int vpo_l_mul_ii(int w0, int w1);
/* fractional multiply without fractional mode (long result) */
#define _l_mul_fract_fb0_ii(w0,w1) \
(vpo_l_mul_ii(w0,w1) << 1)
/* fractional multiply with fractional mode already on (long result) */
#define _l_mul_fract_fb1_ii(w0,w1) \
(vpo_l_mul_ii(w0,w1))
/* fractional multiply without fractional mode (int result) */
#define _i_mul_fract_fb0_ii(w0,w1) \
(vpo_l_mul_ii(w0,w1) >> 15)
/* fractional multiply with fractional mode already on (int result) */
#define _i_mul_fract_fb1_ii(w0,w1) \
(vpo_l_mul_ii(w0,w1) >> 16)
#define _set_fract_bit() vpo_set_fract()
#define _reset_fract_bit() vpo_reset_fract()
#define _set_ovm_bit() vpo_set_ovm()
#define _reset_ovm_bit() vpo_reset_ovm()
#define _l_add_shiftl_li(w0,w1) (((int32)(w0))+(((int32)(int16)(w1))<<16) )
#define _l_sub_shiftl_li(w0,w1) (((int32)(w0))-(((int32)(int16)(w1))<<16) )
#else
/* fractional multiply without fractional mode (long result) */
#define _l_mul_fract_fb0_ii(w0,w1) \
(((long int)w0 * (long int)w1) << 1)
/* fractional multiply with fractional mode already on (long result) */
#define _l_mul_fract_fb1_ii(w0,w1) \
(((long int)w0 * (long int)w1))
/* fractional multiply without fractional mode (int result) */
#define _i_mul_fract_fb0_ii(w0,w1) \
(((long int)w0 * (long int)w1) >> 15)
/* fractional multiply with fractional mode already on (int result) */
#define _i_mul_fract_fb1_ii(w0,w1) \
(((long int)w0 * (long int)w1) >> 16)
#define _set_fract_bit() asm(" ssbx frct")
#define _reset_fract_bit() asm(" rsbx frct")
#define _set_ovm_bit() asm(" ssbx ovm")
#define _reset_ovm_bit() asm(" rsbx ovm")
#endif /* VPO */
#endif /* INTRINSICS_H */
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