qam edits

FFT/ffttp.c

@@ -0,0 +1,79 @@
+#include <math.h>
+#include <stdio.h>
+#include <complex.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+complex float* fft(complex float* p, uint32_t N) {
+    complex float w = cexpf(-2 * I * M_PI / N);
+
+    if (N == 1)
+        return p;
+
+    complex float* pe = (complex float*)malloc(sizeof(complex float) * (N / 2));
+    complex float* po = (complex float*)malloc(sizeof(complex float) * (N / 2));
+    for (int i = 0; i < N - 1; i += 2) {
+       pe[i / 2] = p[i];
+       po[i / 2] = p[i + 1];
+    }
+
+    complex float* xe = fft(pe, N / 2);
+    complex float* xo = fft(po, N / 2);
+
+    complex float* ps = (complex float*)malloc(sizeof(complex float) * N);
+
+    for (int i = 0; i < N / 2; i++) {
+        ps[i] = xe[i] + cpowf(w, (complex float)i) * xo[i];
+        ps[i + N / 2] = xe[i] - cpowf(w, (complex float)i) * xo[i];
+    }
+    
+    return ps;
+}
+
+int main() {
+    FILE *f = fopen("signal.csv","r");
+    if (!f) { perror("signal.csv"); return 1; }
+
+    double t, a;
+    int capacity = 1024, n = 0;
+    complex float *samples = malloc(sizeof(complex float) * capacity);
+
+    while (fscanf(f, "%lf;%lf", &t, &a) == 2) {
+        if (n >= capacity) {
+            capacity *= 2;
+            samples = realloc(samples, sizeof(complex float)*capacity);
+        }
+        samples[n++] = a; 
+    }
+    fclose(f);
+
+    int fsize = 1 << (int)floorf(log2f((float)n));
+
+    complex float* cwav_data = (complex float*)malloc(sizeof(complex float) * fsize);
+    for (int i = 0; i < fsize; i++)
+        cwav_data[i] = samples[i];
+
+    complex float* ft = fft(cwav_data, fsize);
+
+    double Fe = 400.0; 
+
+    FILE *gnuplot = popen("gnuplot -persistent", "w");
+    fprintf(gnuplot, "set title 'fft'\n");
+    fprintf(gnuplot, "set logscale x\n");
+    fprintf(gnuplot, "set logscale y\n");
+    fprintf(gnuplot, "plot '-' with linespoints title 'fft'\n");
+
+    for (int i = 0; i < fsize/2; i++) {
+        double freq = (double)i * Fe / fsize;
+        fprintf(gnuplot, "%f %f\n", freq ,cabsf(ft[i])); 
+    }
+    fprintf(gnuplot, "e\n");
+    pclose(gnuplot);
+
+    free(samples);
+    free(cwav_data);
+    free(ft);
+
+    return 0;
+}
+