c2000 fft代码

以下是C2000的FFT代码示例：

#include "F28x_Project.h"
#include "math.h"

#define N 32
#define PI 3.14159265358979323846

#pragma DATA_SECTION(x, "ramgs0")
#pragma DATA_SECTION(y, "ramgs1")
#pragma DATA_SECTION(w, "ramgs2")

float x[N], y[N];
float w[N];

int main(void)
{
    InitSysCtrl();
    InitGpio();
    
    int i;

    // Generate input signal
    for (i = 0; i < N; i++)
    {
        x[i] = sin(2 * PI * i / N) + 0.5 * sin(4 * PI * i / N);
        y[i] = 0;
    }

    // Generate twiddle factors
    for (i = 0; i < N; i++)
    {
        w[i] = cos(2 * PI * i / N) - sin(2 * PI * i / N) * I;
    }

    // Perform FFT
    fft(x, y, w, N);

    // Print output
    for (i = 0; i < N; i++)
    {
        printf("X[%d] = %.4f + %.4fj\n", i, x[i], y[i]);
    }

    while(1) {}
}

void fft(float *x, float *y, float *w, int n)
{
    int i, j, k, n1, n2;
    float xr, xi, yr, yi;

    // Bit-reverse the input
    j = 0;
    for (i = 0; i < n - 1; i++)
    {
        if (i < j)
        {
            xr = x[j];
            xi = y[j];
            x[j] = x[i];
            y[j] = y[i];
            x[i] = xr;
            y[i] = xi;
        }
        k = n / 2;
        while (k <= j)
        {
            j -= k;
            k /= 2;
        }
        j += k;
    }

    // Perform the FFT
    n1 = 0;
    n2 = 1;
    for (i = 0; i < log2(n); i++)
    {
        n1 = n2;
        n2 *= 2;
        for (j = 0; j < n1; j++)
        {
            for (k = j; k < n; k += n2)
            {
                xr = x[k];
                xi = y[k];
                yr = creal(w[i * n / n2]) * x[k + n1] - cimag(w[i * n / n2]) * y[k + n1];
                yi = creal(w[i * n / n2]) * y[k + n1] + cimag(w[i * n / n2]) * x[k + n1];
                x[k] = xr + yr;
                y[k] = xi + yi;
                x[k + n1] = xr - yr;
                y[k + n1] = xi - yi;
            }
        }
    }
}

这个代码使用了C语言标准库和C2000的DSP库来实现FFT。输入信号是一个长度为N的实数数组，输出是一个长度为N的复数数组。在代码中，`fft`函数实现了FFT算法，`x`和`y`数组存储输入和输出数据，`w`数组存储旋转因子。在主函数中，先生成输入信号，然后调用`fft`函数计算FFT，最后输出结果。