attemp to use a pll

lib/filters.h

@@ -3,6 +3,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include "constants.h"
+#include "oscillator.h"
 
 typedef struct
 {
@@ -13,4 +14,21 @@ typedef struct
 void init_preemphasis(ResistorCapacitor *filter, float tau, float sample_rate);
 float apply_preemphasis(ResistorCapacitor *filter, float sample);
 
-float hard_clip(float sample, float threshold);
+float hard_clip(float sample, float threshold);
+
+typedef struct {
+    float phase_error;
+    float loop_filter;
+    float vco_phase;
+    float vco_frequency;
+
+    float reference_frequency;
+    float target_frequency;
+    float multiplier;
+    float sample_rate;
+    float loop_gain;
+    float filter_coefficient;
+} PLL;
+
+void init_pll(PLL *pll, float reference_frequency, float target_frequency, float sample_rate);
+float update_pll(PLL *pll, float reference_signal);