FFT works

.gitignore

@@ -1,2 +1,3 @@
 *.raw
 *.py
+*.csv

fft-beacon-finder/.gitignore

@@ -0,0 +1,2 @@
+finder
+!plot.py

fft-beacon-finder/finder.c

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+#include <stdlib.h>
+#include <liquid/liquid.h>
+#include <math.h>
+#include <complex.h>
+#include <stdio.h>
+
+const float SAMPLINGRATE = 1000000.0;
+const float FFT_LEN = 256;
+
+int main() {
+    FILE* output = fopen("output.csv", "w");
+    FILE* input = fopen("input.raw", "r");
+
+    float complex * fft_in = (float complex*) malloc(FFT_LEN * sizeof(float complex));
+    float complex * fft_out = (float complex*) malloc(FFT_LEN * sizeof(float complex));
+
+    // create FFT plan
+    fftplan fft = fft_create_plan(FFT_LEN, fft_in, fft_out, LIQUID_FFT_FORWARD, 0);
+
+    int pos = 0;
+    float in[2];
+    while(fread(in, sizeof(float), 2, input) == 2) {
+        fft_in[pos] = (in[1] + I * in[0]);
+        pos += 1;
+        if(pos == FFT_LEN) {
+            pos = 0;
+            fft_execute(fft);
+
+            float fft_min = cabsf(fft_out[0]);
+            float fft_max = cabsf(fft_out[0]);
+            for(int i = 0; i < FFT_LEN; i++) {
+                float mag = cabsf(fft_out[i]);
+                if(mag < fft_min) {
+                    fft_min = mag;
+                }
+                if(mag > fft_max) {
+                    fft_max = mag;
+                }
+            }
+            //printf("Min: %f Max: %f\n", fft_min, fft_max);
+
+            for(int i = FFT_LEN / 2; i < FFT_LEN; i++) {
+                float mag = cabsf(fft_out[i]);
+                mag = (mag - fft_min) / (fft_max - fft_min);
+                fprintf(output, "%f;", mag);
+            }
+
+            for(int i = 0; i < FFT_LEN / 2; i++) {
+                float mag = cabsf(fft_out[i]);
+                mag = (mag - fft_min) / (fft_max - fft_min);
+                fprintf(output, "%f;", mag);
+            }
+
+
+            fprintf(output, "\n");
+        }
+    }
+
+    fft_destroy_plan(fft);
+    free(fft_in);
+    free(fft_out);
+
+    fclose(output);
+    fclose(input);
+
+    return 0;
+}

fft-beacon-finder/plot.py

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+#!/usr/bin/env python3
+
+from numpy import genfromtxt
+import matplotlib
+import matplotlib.pyplot as plt
+
+def main():
+    data = genfromtxt('output.csv', delimiter=';')
+
+    fig, ax = plt.subplots()
+    im = ax.imshow(data)
+    plt.show()
+
+
+if __name__ == '__main__':
+    main()