change pll settings

README.md

@@ -25,7 +25,7 @@ make
 Done!
 
 # CPU Usage?
-Should run completly fine on a pi 5, right now with the preemp, on a pi 3b, its 20%
+Should run completly fine on a pi 5, right now with the preemp, on a pi 3b, its 32%
 
 # Recommendations
 use a lpf, for example swh-plugins's lowpass_iir, for example:

lib/filters.c

@@ -14,12 +14,12 @@ float hard_clip(float sample, float threshold) {
 	return fmaxf(-threshold, fminf(threshold, sample));
 }
 
-void init_pll(PLL *pll, float freq, float loop_filter_bandwidth, int quadrature_mode, int sample_rate) {
+void init_pll(PLL *pll, float freq, float loop_filter_bandwidth, float damping, int quadrature_mode, int sample_rate) {
 	pll->phase = 0.0f;
 	pll->freq = freq;
 	pll->loop_filter_state = 0.0f;
 	pll->kp = M_2PI * loop_filter_bandwidth;
-	pll->ki = 0.25f * pll->kp * pll->kp;
+	pll->ki = (4.0f*damping*damping) * pll->kp * pll->kp;
 	pll->last_output = 0.0f;
 	pll->sample_rate = sample_rate;
 	pll->quadrature_mode = quadrature_mode;
@@ -29,7 +29,7 @@ float apply_pll(PLL *pll, float ref_sample) {
 	float phase_error;
 
 	float vco_output = sinf(pll->phase);
-	if (pll->quadrature_mode) vco_output = sinf(pll->phase + (M_PI / 2.0f)); // 90 degrees
+	if (pll->quadrature_mode) vco_output = sinf(pll->phase + (M_PI / 2.0f));
 
 	phase_error = ref_sample * pll->last_output;
 

lib/filters.h

@@ -26,5 +26,5 @@ typedef struct {
 	int sample_rate;
 	int quadrature_mode;
 } PLL;
-void init_pll(PLL *pll, float freq, float loop_filter_bandwidth, int quadrature_mode, int sample_rate);
+void init_pll(PLL *pll, float freq, float loop_filter_bandwidth, float damping, int quadrature_mode, int sample_rate);
 float apply_pll(PLL *pll, float ref_sample);

src/fm95.c

@@ -416,7 +416,7 @@ int main(int argc, char **argv) {
 	init_preemphasis(&preemp_r, preemphasis_tau, sample_rate);
 
 	PLL rds2_pll;
-	init_pll(&rds2_pll, 66500, 1, 10000, sample_rate);
+	init_pll(&rds2_pll, 66500, 4000, 2, 1, sample_rate);
 	// #endregion
 
 	signal(SIGINT, stop);