TI DSP FFT库函数

sick

在目录c64plus\dsplib_v210\src\DSP_fft16x16，包含了三个层次的FFT库函数，分别是natural C version， intrinsic C version， serial SA version，最后一个是汇编级。在DSP_fft16x16_d.c中有三个测试用例对比耗时。三个函数用法差不多，例如：

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1. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">void DSP_fft16x16_cn (</span>
   
2. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    const short * ptr_w,</span>
   
3. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    int npoints,</span>
   
4. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    short * ptr_x,</span>
   
5. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    short * ptr_y</span>
   
6. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">);</span>
   
7. 
   
8. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">void test_fft(void)</span>
   
9. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">{</span>
   
10. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    const int N = 512;</span>
    
11. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    short x[2*N], y[2*N], w[2*N];</span>
    
12. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    gen_twiddle_fft16x16(w, N);</span>
    
13. 
    
14. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    double fs = 8000.0, f1 = 114.8, f2 = 186.2;</span>
    
15. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    short x8k[8000];</span>
    
16. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    for (int i=0; i<8000; ++i)</span>
    
17. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x8k[i] = 1800.0 * (cos(2*PI*f1*i/fs) + cos(2*PI*f2*i/fs));</span>
    
18. 
    
19. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    short x5[500]; // downsample</span>
    
20. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    for (int i=0; i<500; ++i)</span>
    
21. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x5[i] = x8k[16*i];</span>
    
22. 
    
23. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    int k = 0;</span>
    
24. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    for (; k<6; k++) {</span>
    
25. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x[2*k + 0] = 0;</span>
    
26. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x[2*k + 1] = 0;</span>
    
27. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    }</span>
    
28. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    for (; k<106; k++) {</span>
    
29. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x[2*k + 0] = x5[k-6];</span>
    
30. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">        x[2*k + 1] = 0;</span>
    
31. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    }</span>
    
32. <span style="color: rgb(51, 51, 51); font-family: " microsoft="" yahei";"="">    for (; k</span><n; k++)="" {
    
33.          x[2*k + 0] = 0;
    
34.         x[2*k + 1] = 0;
    
35.     }
    
36. 
    
37.     DSP_fft16x16_cn(w, N, x, y);
    
38.     for (int i=0; i<n; ++i)="" {
    
39.          printf("%d\n", y[2*i]);
    
40.         printf("%d\n", y[2*i+1]);
    
41.     }
    
42. }</n;></n;>

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