/* ======================================================================== */ /* TEXAS INSTRUMENTS, INC. */ /* */ /* NAME */ /* tw_fftSPxSP_C67 */ /* */ /* USAGE */ /* This is a stand-alone program intended to generate twiddle-factor */ /* arrays for the C67x DSPF_sp_fftSPxSP library routine. */ /* It is called as follows: */ /* */ /* tw_fftSPxSP_C67 N > outputfile.c */ /* */ /* The argument 'N' specifies the size of the FFT. This value */ /* must be a power of 2. */ /* */ /* This program will generate the twiddle factor array 'w' and */ /* output the result to the display. Redirect the output to */ /* a file as shown above. */ /* */ /* DESCRIPTION */ /* This program contains the twiddle-factor generation routine */ /* that is described within the source code for the C67x DSPLIB */ /* FFT functions DSPF_sp_fftSPxSP It does not */ /* produce appropriate twiddle-factor arrays for the other FFT */ /* implementations. */ /* */ /* Please consult the specific FFT that you are using for details. */ /* */ /* The final twiddle-factor array generated by the routine will */ /* be 2 * N elements long. */ /* */ /* NOTES */ /* The code below may be adapted to run directly on the target, */ /* rather than running as a separate program running off-line. */ /* Such adaptation is not recommended for time-critical applications. */ /* To adapt this program, remove the 'usage' and 'main' functions, */ /* and call 'gen_twiddle' directly. */ /* */ /* ------------------------------------------------------------------------ */ /* Copyright (c) 2001 Texas Instruments, Incorporated. */ /* All Rights Reserved. */ /* ======================================================================== */ #include #include #include #include #include #ifndef PI # ifdef M_PI # define PI M_PI # else # define PI 3.14159265358979323846 # endif #endif /* ======================================================================== */ /* GEN_TWIDDLE -- Generate twiddle factors for TI's custom FFTs. */ /* */ /* USAGE */ /* This routine is called as follows: */ /* */ /* int gen_twiddle(float *w, int n) */ /* */ /* short *w Pointer to twiddle-factor array */ /* int n Size of FFT */ /* */ /* The routine will generate the twiddle-factors directly into the */ /* array you specify. The array needs to be approximately 2*N */ /* elements long. (The actual size, which is slightly smaller, is */ /* returned by the function.) */ /* ======================================================================== */ int gen_twiddle(float *w, int n) { int i, j, k; for (j = 1, k = 0; j < n >> 2; j = j << 2) { for (i = 0; i < n >> 2; i += j) { w[k + 5] = sin(6.0 * PI * i / n); w[k + 4] = cos(6.0 * PI * i / n); w[k + 3] = sin(4.0 * PI * i / n); w[k + 2] = cos(4.0 * PI * i / n); w[k + 1] = sin(2.0 * PI * i / n); w[k + 0] = cos(2.0 * PI * i / n); k += 6; } } return k; } /* ======================================================================== */ /* USAGE -- Print usage information and optionally an error message. */ /* ======================================================================== */ void usage(char *error) { fprintf(stderr, " \n" "USAGE \n" " This is a stand-alone program intended to generate twiddle-factor \n" " arrays for the C67x DSPF_sp_fftSPxSP FFT library routines. \n" " It is called as follows: \n" " \n" " tw_fftSPxSP_C67 N > outputfile.c \n" " \n" " The argument 'N' specifies the size of the FFT. This value \n" " must be a power of 2. \n" " \n" " This program will generate the twiddle factor array 'w' and \n" " output the result to the display. Redirect the output to \n" " a file as shown above. \n" " \n"); if (error) fprintf(stderr, "ERROR: %s\n", error); exit(1); } /* ======================================================================== */ /* MAIN -- Where the action happens. */ /* ======================================================================== */ int main(int argc, char *argv[]) { int i, n = -1, size; int is_pow_2 = 0; float *w; char *s; char buf[80]; /* -------------------------------------------------------------------- */ /* Parse the arguments. */ /* -------------------------------------------------------------------- */ if (argc < 2) { usage(NULL); } while (argc-->1) { if (!isdigit(argv[1][0]) || sscanf(argv[1], "%d", &n) != 1) { sprintf(buf, "Unrecognized argument: %-.32s\n", argv[1][0]); usage(buf); } if (n < 16 || n > 32768) usage("FFT size must be between 16 and 32768 points."); for (i = 2; i < 24; i++) if ((1 << i) == n) break; is_pow_2 = !(i & 1); if (i >= 24) { usage("FFT size must be a power of 2\n"); exit(1); } } if (n == -1) usage("Must specify FFT size."); /* -------------------------------------------------------------------- */ /* Allocate memory for the FFT twiddle factors. */ /* -------------------------------------------------------------------- */ w = calloc(2 * sizeof(float), n); if (!w) { fprintf(stderr, "ERROR: Unable to allocate memory for " "twiddle factors\n"); exit(1); } /* -------------------------------------------------------------------- */ /* Generate the twiddle-factor array. */ /* -------------------------------------------------------------------- */ size = gen_twiddle(w, n); /* -------------------------------------------------------------------- */ /* Print out the resulting twiddle factors. */ /* -------------------------------------------------------------------- */ printf( "/* -------------------------------------------------------------------- */\n" "/* Automatically generated twiddle-factor array. */\n" "/* Number of points: %-5d */\n" "/* Appropriate FFTs: C67x DSPF_sp_fftSPxSP */\n" "/* Required alignment: 8 byte (double-word) */\n" "/* -------------------------------------------------------------------- */\n", n); printf("#pragma DATA_ALIGN(w, 8);\n"); printf("const float w[2 * %d] =\n{", size / 2); for (i = 0; i < size; i++) { printf("%s%c%f", i == 0 ? "\n " : (i & 7) == 0 ? ",\n " : ", ", w[i] < 0 ? '-' : ' ', fabs(w[i])); } printf("\n};\n"); return 0; }