From cdca13f412ec840013aedd798d85591d9a4a57eb Mon Sep 17 00:00:00 2001
From: Gordon JC Pearce <gordonjcp@gmail.com>
Date: Thu, 12 Sep 2024 15:10:16 +0100
Subject: [PATCH] workingish highpass filter

---
 plugin/chassis.cpp    | 21 +++++++++++++++++++++
 plugin/parameters.cpp |  9 +++++----
 plugin/voice.hpp      |  1 +
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/plugin/chassis.cpp b/plugin/chassis.cpp
index 80ee5e1..ef92e13 100644
--- a/plugin/chassis.cpp
+++ b/plugin/chassis.cpp
@@ -159,6 +159,27 @@ void Chassis::run(const float **, float **outputs, uint32_t frames, const MidiEv
         s.blockLeft -= sizeThisTime;
     }
 
+    // highpass filter
+
+    float tmp = s.hptmp;
+    float smp, flt=0;
+    float cut_tbl[4] = {0.91245, 0.97097, 1, 0.99088};
+    float cut = cut_tbl[(s.patchRam.switch2 & 0x18) >> 3];
+    float gain_tbl[4] = {-1, -1, 0, 4};
+    float gain = gain_tbl[(s.patchRam.switch2 & 0x18) >> 3];
+
+   // printf("hp= %02x\n", (s.patchRam.switch2 & 0x18)>>3);
+    
+    for (uint32_t i = 0; i < frames; i++) {
+        smp = outputs[0][i];
+        
+        flt = ((tmp - smp) * cut) + smp;
+        tmp = flt;
+        outputs[0][i] = ((flt * gain) + smp);
+    }   
+    s.hptmp = flt;
+
+
     // copy left to right
     memmove(outputs[1], outputs[0], sizeof(float) * frames);
     // outputs[1][1]=1;
diff --git a/plugin/parameters.cpp b/plugin/parameters.cpp
index 2552df6..012adf1 100644
--- a/plugin/parameters.cpp
+++ b/plugin/parameters.cpp
@@ -149,7 +149,7 @@ void Chassis::initParameter(uint32_t index, Parameter& parameter) {
             parameter.name = "HPF";
             parameter.symbol = "ch_hpf";
             parameter.ranges.min = 0.0f;
-            parameter.ranges.max = 3.0f;
+            parameter.ranges.max = 3.9f;
             parameter.ranges.def = 0.0f;
             parameter.midiCC = 20;
             break;
@@ -397,9 +397,10 @@ void Chassis::setParameterValue(uint32_t index, float value) {
 
         case paramHPF:  // bits 3-4 of switch 2
             // doesn't look great in Carla because of odd behaviour with small integer knobs
+            printf("setPV %d %f\n", index, value);
             if (value > 3) value = 3;
-            s.patchRam.switch2 &= 0xf3;
-            s.patchRam.switch2 |= (int)value << 3;
+            s.patchRam.switch2 &= 0xe7;
+            s.patchRam.switch2 |= (3-(int)value )<< 3;
             break;
 
         case paramModWheel:
@@ -452,7 +453,7 @@ float Chassis::getParameterValue(uint32_t index) const {
             return s.patchRam.noise;
             break;
         case paramHPF:
-            return (s.patchRam.switch2 & 0x18) >> 3;
+            return 3-((s.patchRam.switch2 & 0x18) >> 3);
             break;
         case paramVCFFreq:
             return s.patchRam.vcfFreq;
diff --git a/plugin/voice.hpp b/plugin/voice.hpp
index 43f19b0..dce2768 100644
--- a/plugin/voice.hpp
+++ b/plugin/voice.hpp
@@ -133,6 +133,7 @@ class Synth {
     } patchRam;
 
     float pitchCV[104];
+    float hptmp;
 
     void runLFO();
     void lfoDelay();