From bdd8c21fcfff8041ea94a972903ce42e58c2a5c2 Mon Sep 17 00:00:00 2001
From: ozpv <39195175+ozpv@users.noreply.github.com>
Date: Sat, 29 Aug 2026 23:04:49 -0500
Subject: add retain

---
 Core/Src/Effects/ringmod.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

(limited to 'Core/Src/Effects/ringmod.c')

diff --git a/Core/Src/Effects/ringmod.c b/Core/Src/Effects/ringmod.c
index 1b411dc..be58c11 100755
--- a/Core/Src/Effects/ringmod.c
+++ b/Core/Src/Effects/ringmod.c
@@ -7,11 +7,17 @@
 
 #include "cs4272.h"
 #include "ringmod.h"
-#include <math.h>
-#include <float.h>
+#include "arm_math.h"
 
 /* MF-102S ring modulator */
-void ringmod(float *samples, const size_t range_min, const size_t range_max, const struct RingModParams *params) {
+void ringmod(
+    const struct RingModParams *params,
+    const int32_t *samples_in,
+    int32_t *samples_out,
+    const size_t range_min,
+    const size_t range_max,
+    const enum Channel channel
+) {
     static float lfo_phase = 0.0f;
     static float carrier_phase = 0.0f;
 
@@ -19,23 +25,30 @@ void ringmod(float *samples, const size_t range_min, const size_t range_max, con
     const float inverse_sample_rate = 1.0f / sample_rate;
 
     /* samples are interleaved */
-    for (size_t i = range_min; i < range_max; i += 2) {
+    for (size_t i = range_min + channel; i < range_max; i += 2) {
+        float sample = int24_t_to_f32(samples_in[i]);
+
         float frequency_lfo = 0.0f;
 
         if (params->square_lfo) {
             frequency_lfo = (lfo_phase < 0.5f) ? params->lfo_amount : -params->lfo_amount;
         } else {
-            frequency_lfo = params->lfo_amount * sinf(M_TWOPI * lfo_phase);
+            frequency_lfo = params->lfo_amount * arm_sin_f32(M_TWOPI * lfo_phase);
         }
 
-        float carrier = sinf(M_TWOPI * carrier_phase);
+        float carrier = arm_sin_f32(M_TWOPI * carrier_phase);
 
-        samples[i] = (samples[i] * (1.0f - params->mix)) + (samples[i] * carrier * params->mix);
+        float output_sample = (sample * (1.0f - params->mix)) + (sample * carrier * params->mix);
+        samples_out[i] = f32_to_int24_t(output_sample);
 
         lfo_phase += params->lfo_rate * inverse_sample_rate;
-        lfo_phase = fmod(lfo_phase, 1.0f);
+        while (lfo_phase >= 1.0f) {
+            lfo_phase -= 1.0f;
+        }
 
         carrier_phase += (params->frequency + frequency_lfo) * inverse_sample_rate;
-        carrier_phase = fmod(carrier_phase, 1.0f);
+        while (carrier_phase >= 1.0f) {
+            carrier_phase -= 1.0f;
+        }
     }
 }
-- 
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