added tests with lpf

tests/gensin1.c

@@ -0,0 +1,86 @@
+/*
+ *
+ * Copyright 2022 Oleg Borodin  <borodin@unix7.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ *
+ */
+
+
+#include <stdio.h>
+#include <math.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+
+
+typedef struct {
+    double x0;
+    double x1;
+    double rc;
+} lpf_t;
+
+void lpf_init(lpf_t *lpf, double freq) {
+    lpf->x0 = 0.0;
+    lpf->x1 = 0.0;
+
+    double order = 1.5;
+    double n = 1 / sqrt(pow(2, 1.0 / order) - 1);
+    lpf->rc = 1 / (2 * n * M_PI * freq);
+}
+
+
+double lpf_next(lpf_t *lpf, double x, double dt) {
+
+    double k = dt / (lpf->rc + dt);
+
+    lpf->x1 = lpf->x1 + k * (x - lpf->x1);
+    lpf->x0 = lpf->x0 + k * (lpf->x1 - lpf->x0);
+    return lpf->x0;
+}
+
+int main(int argc, char **argv) {
+
+    double t = 0;
+    double s = 0;
+    double freq1 = 10;
+    double freq2 = 50;
+    double freq3 = 200;
+    double dt = 0.0001;
+    double l = 0.5;
+
+    int fd = open("freq.dat", O_WRONLY | O_TRUNC | O_CREAT, 0666);
+    printf("start\n");
+
+    if (fd < 0) { return 1; };
+
+    lpf_t lpf;
+    lpf_init(&lpf, 30.0);
+
+
+    for (int i = 0; i < (l / dt); i++) {
+        t = i * dt;
+        double s1 = sin(2 * M_PI * freq1 * t);
+        double s2 = cos(2 * M_PI * freq2 * t);
+        double s3 = sin(2 * M_PI * freq3 * t);
+        s = (s1 + s2 + s3) / 3.0;
+        s = lpf_next(&lpf, s, dt);
+        dprintf(fd, "%e\t%e\n", t, s);
+    }
+    fsync(fd);
+    close(fd);
+    return 0;
+}

tests/gensin3.c

@@ -0,0 +1,185 @@
+/*
+ * Copyright 2022 Oleg Borodin  <borodin@unix7.org>
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <complex.h>
+
+typedef struct {
+    double x0;
+    double x1;
+    double rc;
+} lpf_t;
+
+void lpf_init(lpf_t * lpf, double freq) {
+    lpf->x0 = 0.0;
+    lpf->x1 = 0.0;
+
+    double order = 1.5;
+    double n = 1 / sqrt(pow(2, 1.0 / order) - 1);
+
+    lpf->rc = 1 / (2 * n * M_PI * freq);
+}
+
+double lpf_next(lpf_t * lpf, double x, double dt) {
+
+    double k = dt / (lpf->rc + dt);
+
+    lpf->x1 = lpf->x1 + k * (x - lpf->x1);
+    lpf->x0 = lpf->x0 + k * (lpf->x1 - lpf->x0);
+    return lpf->x0;
+}
+
+void dft(double* x1, double* y1, int m, int dir) {
+    long i, k;
+    double arg;
+    double cosarg, sinarg;
+
+    double x2[m];
+    double y2[m];
+
+    for (i = 0; i < m; i++) {
+        x2[i] = 0;
+        y2[i] = 0;
+        arg = -dir * 2.0 * M_PI * (double)i / (double)m;
+        for (k = 0; k < m; k++) {
+            cosarg = cos(k * arg);
+            sinarg = sin(k * arg);
+            x2[i] += (x1[k] * cosarg - y1[k] * sinarg);
+            y2[i] += (x1[k] * sinarg + y1[k] * cosarg);
+        }
+    }
+    if (dir == 1) {
+        for (i = 0; i < m; i++) {
+            x1[i] = x2[i] / (double)m;
+            y1[i] = y2[i] / (double)m;
+        }
+    } else {
+        for (i = 0; i < m; i++) {
+            x1[i] = x2[i];
+            y1[i] = y2[i];
+        }
+    }
+}
+
+
+int main(int argc, char** argv) {
+
+    double t = 0;
+    double s = 0;
+    double freq1 = 20;
+    double freq2 = 70;
+    double freq3 = 150;
+    double dt = 0.001;
+
+    lpf_t lpf;
+
+    lpf_init(&lpf, 20.0);
+
+    int c = 1024 * 4;
+    double xa[c];
+    double xb[c];
+    double y[c];
+
+    for (int i = 0; i < c; i++) {
+        t = i * dt;
+        double s1 = sin(2 * M_PI * freq1 * t);
+        double s2 = cos(2 * M_PI * freq2 * t);
+        double s3 = sin(2 * M_PI * freq3 * t);
+
+        s = (s1 + s2 + s3) / 3.0;
+        xa[i] = s;
+        xb[i] = lpf_next(&lpf, s, dt);;
+    }
+
+    for (int i = 0; i < c; i++) {
+        y[i] = 0;
+    }
+
+    double rate = 1.0 / dt;
+
+
+    FILE * fd;
+
+    fd = popen ("gnuplot -persistent", "w");
+
+    fprintf(fd, "set terminal png size 1600,1200\n");
+    fprintf(fd, "set output \"gensin3a.png\"\n");
+    fprintf(fd, "plot '-' with lines\n");
+
+    dft(xa, y, c, -1);
+    for (int i = 0; i < c; i++) {
+        double freq = rate * (double)i / (double)c;
+        double amp = sqrt(xa[i]*xa[i] + y[i]*y[i]) ;
+        if (freq < rate / 2) {
+            fprintf(fd, "%e %e\n", freq, amp);
+        }
+    }
+    fflush(fd);
+    fprintf(fd, "e");
+    fclose(fd);
+
+    for (int i = 0; i < c; i++) {
+        y[i] = 0;
+    }
+
+
+    fd = popen ("gnuplot -persistent", "w");
+
+    fprintf(fd, "set terminal png size 1600,1200\n");
+    fprintf(fd, "set output \"gensin3b.png\"\n");
+    fprintf(fd, "plot '-' with lines\n");
+
+    dft(xb, y, c, -1);
+    for (int i = 0; i < c; i++) {
+        double freq = rate * (double)i / (double)c;
+        double amp = sqrt(xb[i]*xb[i] + y[i]*y[i]) ;
+        if (freq < rate / 2) {
+            fprintf(fd, "%e %e\n", freq, amp);
+        }
+    }
+    fflush(fd);
+    fprintf(fd, "e");
+    fclose(fd);
+
+
+
+#if 0
+    FILE* fd = fopen("freq1.dat", "w");
+
+    dft(xa, y, c, -1);
+    for (int i = 0; i < c; i++) {
+        double freq = rate * (double)i / (double)c;
+        double amp = sqrt(xa[i]*xa[i] + y[i]*y[i]) ;
+        if (freq < rate / 2) {
+            fprintf(fd, "%e %e\n", freq, amp);
+        }
+    }
+
+    fclose(fd);
+
+    for (int i = 0; i < c; i++) {
+        y[i] = 0;
+    }
+
+    fd = fopen("freq2.dat", "w");
+
+    dft(xb, y, c, -1);
+    for (int i = 0; i < c; i++) {
+        double freq = rate * (double)i / (double)c;
+        double amp = sqrt(xb[i]*xb[i] + y[i]*y[i]);
+        if (freq < rate / 2) {
+            fprintf(fd, "%e %e\n", freq, amp);
+        }
+    }
+
+    fclose(fd);
+#endif
+
+    return 0;
+}