not totally happy with the mixing but saw and square are now switchable

plugin/DistrhoPluginInfo.h

@@ -23,7 +23,7 @@
 #define DISTRHO_PLUGIN_URI "https://gjcp.net/plugins/alphaosc"
 
 #define DISTRHO_PLUGIN_NUM_INPUTS 0
-#define DISTRHO_PLUGIN_NUM_OUTPUTS 2
+#define DISTRHO_PLUGIN_NUM_OUTPUTS 1
 #define DISTRHO_PLUGIN_IS_SYNTH 1
 #define DISTRHO_PLUGIN_IS_RT_SAFE 1
 

plugin/Makefile

@@ -10,6 +10,7 @@
 NAME = alphaosc
 
 FILES_DSP = \
+	parameters.cpp \
 	alphaosc.cpp
 
 

plugin/alphaosc.cpp

@@ -38,6 +38,9 @@ void AlphaOsc::initAudioPort(bool input, uint32_t index, AudioPort &port) {
 void AlphaOsc::activate() {
     // calculate filter coefficients and stuff
     printf("called activate()\n");
+    omega = (1 << 31) / sampleRate * 130;
+    lfoOmega = (1 << 31) / sampleRate * 3.51;
+    omega = (130 / sampleRate) * (1 << 23);
 }
 
 void AlphaOsc::deactivate() {
@@ -48,8 +51,109 @@ void AlphaOsc::run(const float **, float **outputs, uint32_t frames, const MidiE
     bzero(outputs[0], sizeof(float) * frames);
 
     // cast unused parameters to void for now to stop the compiler complaining
-    (void) midiEventCount;
+    (void)midiEventCount;
-    (void) midiEvents;
+    (void)midiEvents;
+
+    uint16_t i;
+    uint32_t osc;
+    uint8_t lfo;
+    float saw, sqr, sub, wave;
+    float oct1, oct3, pwg;
+
+    float out, in;
+
+    // calculate an entire block of samples
+
+    for (i = 0; i < frames; i++) {
+        // increment phase of saw counter
+        // phase is a 32-bit counter because we're on a PC and we can afford to be profligate with silicon
+        // the actual Alpha Juno oscillators might well have been 8-bit for reasons loosely explained in the README
+
+        phase += omega;
+        lfoPhase += lfoOmega;
+
+        // now osc is a ten-bit counter, to give room for the sub osc outputs
+        // square output will be bit 7 of osc, 25% will be bit 7 & bit 6
+        // PWM square will be bit 7 & comparator, with the PWM being compared against bits 0-6
+        osc = phase >> 14;
+
+        // LFO is 7-bit triangle
+        lfo = (lfoPhase >> 24) & 0x7f;
+        lfo = (lfoPhase & 0x80000000) ? lfo : 127 - lfo;
+
+        pw = 0;
+
+        // the oscillator outputs in the chip are probably digital signals
+        // with the saw being the 8-bit outputs of the counter
+        // the square and sub signals picked off the counter bits
+        // and a couple of flipflops to generate the sub osc signals
+
+        // 8-bit saw scaled
+        saw = (osc & 0xff) / 256.0f;
+
+        // square scaled to 0-1, along with one and three octaves up
+        sqr = (float)(osc & 0x80) != 0;
+        oct1 = (float)(osc & 0x40) != 0;
+        oct3 = (float)(osc & 0x10) != 0;
+
+        // pulse width gate
+        // lower seven bits of the saw osc, compared with PW setting
+        pw = lfo*0.5;
+        pwg = (float)((osc & 0x7f) >= pw) != 0;
+
+        // calculate the oscillator output
+        in = wave = 0;
+        switch (sqrmode) {
+            case 0:
+            case 4:
+                wave = 0;
+                break;    // oscillator is off
+            case 1:
+                wave = sqr;
+                break;
+            case 2:
+                wave = sqr * oct1;   // 25% pulse
+                break;
+            case 3:
+                wave = sqr * pwg;    // pwm
+                break;
+        }
+
+        in += (wave * 0.63); // scaled similarly to Juno 106
+
+        switch (sawmode) {
+            case 0:
+                wave = 0;
+                break;    // oscillator is off
+            case 1:
+                wave = saw;
+                break;
+            case 2:
+                wave = saw * oct1;   // pulsed
+                break;
+            case 3:
+                wave = saw * pwg;    // pwm
+                break;
+            case 4:
+                wave = saw * oct3;   // oct3 pulse
+                break;
+            case 5:
+                wave = saw * oct1 * oct3;    // both pulse
+                break;
+        }
+
+        in += (wave * 0.8); // scaled similarly to Juno 106
+
+        // DC removal highpass filter
+        // this is very approximately 6Hz at 44.1kHz and 48kHz
+        // honestly it doesn't matter all that much if it's wrong at higher sample rates
+        out = in - hpfx + .99915 * hpfy;
+        hpfx = in;
+        hpfy = out;
+
+        outputs[0][i] = out;
+    }
+   // printf("%f %f\n", sqr, saw);
 }
 
 // create the plugin

plugin/alphaosc.hpp

@@ -25,8 +25,12 @@ START_NAMESPACE_DISTRHO
 class AlphaOsc : public Plugin {
    public:
     enum Parameters {
-        paramLFORate,
+        pSqrMode,
-        paramLFODelay,
+        pSawMode,
+        //pSubMode,
+
+        //pLFORate,
+        //pLFODepth,
 
         parameterCount
     };
@@ -45,10 +49,10 @@ class AlphaOsc : public Plugin {
 
     // Initialisation
     void initAudioPort(bool input, uint32_t index, AudioPort &port) override;
-    //void initParameter(uint32_t index, Parameter &parameter) override;
 
-    //void setParameterValue(uint32_t index, float value) override;
+    void initParameter(uint32_t index, Parameter &parameter) override;
-    //float getParameterValue(uint32_t index) const override;
+    void setParameterValue(uint32_t index, float value) override;
+    float getParameterValue(uint32_t index) const override;
 
     // Processing
     void activate() override;
@@ -58,11 +62,16 @@ class AlphaOsc : public Plugin {
 
    private:
     double sampleRate;
-    uint32_t omega;
+    uint32_t omega, lfoOmega;
-    uint32_t phase;
+    uint32_t phase, lfoPhase;
+
+    uint8_t pw;
+
+    uint8_t sqrmode, sawmode, submode;
+
+    float hpfx, hpfy;
 
     DISTRHO_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR(AlphaOsc);
 };
 
-END_NAMESPACE_DISTRHO
+END_NAMESPACE_DISTRHO
-  

plugin/parameters.cpp

@@ -0,0 +1,103 @@
+/*
+   Alpha Oscillator POC
+
+   Copyright 2024 Gordon JC Pearce <gordonjcp@gjcp.net>
+
+   Permission to use, copy, modify, and/or distribute this software for any
+   purpose with or without fee is hereby granted, provided that the above
+   copyright notice and this permission notice appear in all copies.
+
+   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+   SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+   OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+   CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "alphaosc.hpp"
+
+void AlphaOsc::initParameter(uint32_t index, Parameter& parameter) {
+    // define all the different control input parameters
+    switch (index) {
+        case pSqrMode:
+            // set up Square slider
+            parameter.hints = kParameterIsAutomatable | kParameterIsInteger;
+            parameter.name = "Square";
+            parameter.symbol = "ao_sqr";
+            parameter.ranges.min = 0.0f;
+            parameter.ranges.max = 4.0f;
+            parameter.ranges.def = 1.0f;
+            parameter.enumValues.count = 5;
+            parameter.enumValues.restrictedMode = true;
+            {
+                ParameterEnumerationValue* const enumValues = new ParameterEnumerationValue[5];
+                enumValues[0].value = 0;
+                enumValues[0].label = "Off";
+                enumValues[1].value = 1;
+                enumValues[1].label = "50%";
+                enumValues[2].value = 2;
+                enumValues[2].label = "25%";
+                enumValues[3].value = 3;
+                enumValues[3].label = "PWM";
+                // dummy value because Carla won't display integer knobs with less than 5 steps
+                enumValues[4].value = 3;
+                enumValues[4].label = "Off";
+                parameter.enumValues.values = enumValues;
+            }
+            break;
+        case pSawMode:
+            // set up Saw slider
+            parameter.hints = kParameterIsAutomatable | kParameterIsInteger;
+            parameter.name = "Saw";
+            parameter.symbol = "ao_saw";
+            parameter.ranges.min = 0.0f;
+            parameter.ranges.max = 5.0f;
+            parameter.ranges.def = 1.0f;
+            parameter.enumValues.count = 6;
+            parameter.enumValues.restrictedMode = true;
+            {
+                ParameterEnumerationValue* const enumValues = new ParameterEnumerationValue[6];
+                enumValues[0].value = 0;
+                enumValues[0].label = "Off";
+                enumValues[1].value = 1;
+                enumValues[1].label = "On";
+                enumValues[2].value = 2;
+                enumValues[2].label = "Oct1";
+                enumValues[3].value = 3;
+                enumValues[3].label = "PWM";
+                enumValues[3].value = 4;
+                enumValues[3].label = "Oct3";
+                enumValues[3].value = 5;
+                enumValues[3].label = "Oct1+3";
+                parameter.enumValues.values = enumValues;
+            }
+            break;
+    }
+}
+
+void AlphaOsc::setParameterValue(uint32_t index, float value) {
+    switch (index) {
+        case pSqrMode:
+            sqrmode = value;
+            break;
+        case pSawMode:
+            sawmode = value;
+            break;
+    }
+    // we don't need to handle a default condition
+    // if there's a parameter left unhandled, it's probably
+    // a mistake by the plugin host, and we don't much care
+}
+
+float AlphaOsc::getParameterValue(uint32_t index) const {
+    switch (index) {
+        case pSqrMode:
+            return sqrmode;
+        case pSawMode:
+            return sawmode;
+    }
+    // if we fall all the way through...
+    return 0;
+}