Several fixes.

Hopefully working interpolation (Catmull currently does not work because of too high CPU usage and xruns).

MicroMDAEPiano.ino

@@ -150,6 +150,10 @@ elapsedMillis eeprom_master_volume_update_timer;
 elapsedMillis cpu_mem_millis;
 #endif
 
+#ifdef DEBUG_AUDIO
+elapsedMillis debug_audio_timer;
+#endif
+
 // Allocate the delay lines for left and right channels
 short l_delayline[CHORUS_DELAY_LENGTH_SAMPLES];
 short r_delayline[CHORUS_DELAY_LENGTH_SAMPLES];
@@ -232,6 +236,10 @@ void setup()
   modulator.offset(0.0);
   modulator_filter.setLowpass(0, CHORUS_MODULATOR_FILTER_FRQ, CHORUS_MODULATOR_FILTER_Q);
   inverter.gain(-1.0); // change phase for second modulated delay (faked stereo mode)
+  modchorus_r.offset(15.0);
+  modchorus_r.intensity(1.0);
+  modchorus_l.offset(15.0);
+  modchorus_l.intensity(1.0);
 
   // internal mixing of original signal(0), reverb(1) and chorus(2)
   mixer_r.gain(VOL_MAIN, 0.5);
@@ -244,6 +252,9 @@ void setup()
   // set master volume
   set_master_volume(master_volume);
 
+  // init random generator
+  srand(analogRead(A0));
+
         Serial.println(F("<setup end>"));
 
 #if defined (SHOW_DEBUG) && defined (SHOW_CPU_LOAD_MSEC)
@@ -319,9 +330,17 @@ void loop()
     if ( eeprom_config_update_flag > 0 && ep->getActiveVoices() == 0) // write only to eeprom when no voice is active
       eeprom_config_update();
 
-    if (eeprom_master_volume_update_flag == true && eeprom_master_volume_update_timer > STORE_MASTER_VOLUME_MS)
+    if (eeprom_master_volume_update_flag == true && eeprom_master_volume_update_timer > STORE_MASTER_VOLUME_MS && ep->getActiveVoices() == 0)
       eeprom_master_volume_update();
   }
+
+#ifdef DEBUG_AUDIO
+  if (debug_audio_timer > DEBUG_AUDIO)
+  {
+    ep->noteOn(60 + rand() % 108, rand() % 128);
+    debug_audio_timer = 0;
+  }
+#endif
 }
 
 //*************************************************************************************************

UI.hpp

@@ -45,6 +45,7 @@
 #define UI_HPP_INCLUDED
 #include <LiquidCrystal_I2C.h>
 #include <LiquidMenu.h>
+#define BOUNCE_WITH_PROMPT_DETECTION
 #include <Bounce.h>
 #include "Encoder4.h"
 #include "config.h"
@@ -2046,8 +2047,8 @@ void set_chorus_delay(uint8_t value)
   Serial.print(F("Set CHORUS_DELAY "));
   Serial.println(value);
 #endif
-  modchorus_r.setDelay(float(value / 10));
-  modchorus_l.setDelay(float(value / 10));
+  modchorus_r.offset(20.0);
+  modchorus_l.intensity(1.0);
   configuration.chorus_delay = value;
 }
 

config.h

@@ -60,8 +60,10 @@
 #define CHORUS_WAVEFORM WAVEFORM_TRIANGLE // WAVEFORM_SINE WAVEFORM_TRIANGLE WAVEFORM_SAWTOOTH WAVEFORM_SAWTOOTH_REVERSE
 #define CHORUS_MODULATOR_FILTER_FRQ 1000
 #define CHORUS_MODULATOR_FILTER_Q 0.7
-#define CHORUS_INTERPOLATION_MODE Catmull
-#define CHORUS_INTERPOLATION_WINDOW_SIZE 11
+//#define CHORUS_INTERPOLATION_MODE 0       // no interpolation
+#define CHORUS_INTERPOLATION_MODE 1       // linear interpolation
+//#define CHORUS_INTERPOLATION_MODE Catmull   // spline interpolation
+#define CHORUS_INTERPOLATION_WINDOW_SIZE 3  // only uneven numbers bigger than 3!!!
 
 //*************************************************************************************************
 //* DEBUG OUTPUT SETTINGS
@@ -71,6 +73,7 @@
 #define SERIAL_SPEED 38400
 #define SHOW_XRUN 1
 #define SHOW_CPU_LOAD_MSEC 5000
+#define DEBUG_AUDIO 50
 
 //*************************************************************************************************
 //* HARDWARE SETTINGS
@@ -138,7 +141,7 @@
 //* DO NO CHANGE ANYTHING BEYOND IF YOU DON'T KNOW WHAT YOU ARE DOING !!!
 //*************************************************************************************************
 
-#define MICRO_MDAEPIANO_VERSION "0.9.4"
+#define MICRO_MDAEPIANO_VERSION "0.9.5"
 
 #define MAX_SOUNDS min(99,int((4096-EEPROM_CONFIGURATIONS)/sizeof(config_t)))
 
@@ -301,7 +304,7 @@
 // Engine
 #if defined(__MK66FX1M0__)
 // Teensy-3.6 settings
-#define NVOICES 48
+#define NVOICES 40
 #else
 #define NVOICES 32
 #endif

effect_modulated_delay.cpp

@@ -46,6 +46,8 @@ boolean AudioEffectModulatedDelay::begin(short *delayline, int d_length)
 
   _delayline = NULL;
   _delay_length = 0;
+  _delay_offset = 0.0;
+  _modulation_intensity = 0.0;
   _circ_idx = 0;
 
   if (delayline == NULL) {
@@ -56,7 +58,13 @@ boolean AudioEffectModulatedDelay::begin(short *delayline, int d_length)
   }
 
   _delayline = delayline;
-  _delay_length = _max_delay_length = d_length;
+  _delay_length = d_length;
+
+#ifdef CHORUS_INTERPOLATION_MODE
+  spline = new Spline;
+  spline->setPoints(x, y, int(CHORUS_INTERPOLATION_WINDOW_SIZE));
+  spline->setDegree(CHORUS_INTERPOLATION_MODE);
+#endif
 
   return (true);
 }
@@ -81,9 +89,7 @@ void AudioEffectModulatedDelay::update(void)
     float mod_fraction;
 #ifdef CHORUS_INTERPOLATION_MODE
     int8_t j;
-    float x[CHORUS_INTERPOLATION_WINDOW_SIZE];
-    float y[CHORUS_INTERPOLATION_WINDOW_SIZE];
-    Spline spline(x, y, CHORUS_INTERPOLATION_WINDOW_SIZE, CHORUS_INTERPOLATION_MODE);
+    uint8_t c;
 #endif
 
     bp = block->data;
@@ -96,16 +102,15 @@ void AudioEffectModulatedDelay::update(void)
         _circ_idx = 0;
       _delayline[_circ_idx] = *bp;
 
-      // Calculate modulation index as a float, for interpolation later.
+      // Calculate the modulation index as a float in the interval [-1.0,1.0] for interpolation later.
       // The index is located around the half of the delay length multiplied by the current amount of the modulator
-      mod_idx = *mp * float(_delay_length >> 1);
+      mod_idx = _delay_offset + ((float(*mp) / SHRT_MAX) * _modulation_intensity);
       mod_fraction = modff(mod_idx, &mod_number);
 #ifdef CHORUS_INTERPOLATION_MODE
       // Spline interpolation
       // Generate a an array with the size of CHORUS_INTERPOLATION_WINDOW_SIZE of x/y values around mod_idx for interpolation
-      uint8_t c = 0;
       int16_t c_mod_idx = _circ_idx - int(round(mod_idx)); // This is the pointer to the value in the circular buffer at the current modulation index
-      for (j = (CHORUS_INTERPOLATION_WINDOW_SIZE / -2); j <= (CHORUS_INTERPOLATION_WINDOW_SIZE / 2); j++)
+      for (j = (CHORUS_INTERPOLATION_WINDOW_SIZE / -2), c = 0; j <= (CHORUS_INTERPOLATION_WINDOW_SIZE / 2); j++, c++)
       {
         int16_t jc_mod_idx = (c_mod_idx + j) % _delay_length; // The modulation index pointer plus the value of the current window pointer
         if (jc_mod_idx < 0) // check for negative offsets and correct them
@@ -113,9 +118,8 @@ void AudioEffectModulatedDelay::update(void)
         else
           y[c] = float(_delayline[jc_mod_idx]);
         x[c] = float(j);
-        c++;
       }
-      *bp = int(round(spline.value(mod_fraction))); // use spline interpolated value
+      *bp = int(round(spline->value(mod_fraction))); // use spline interpolated value
 #else
       // Simple interpolation
       int16_t c_mod_idx = (_circ_idx + int(round(mod_idx))) % _delay_length;
@@ -131,7 +135,12 @@ void AudioEffectModulatedDelay::update(void)
         value1 = _delayline[c_mod_idx - 1];
         value2 = _delayline[c_mod_idx];
       }
+
+      if (mod_fraction < 0)
+        *bp = int(round((1.0 + mod_fraction) * value1 + fabs(mod_fraction) * value2));
+      else
         *bp = int(round(mod_fraction * value1 + (1.0 - mod_fraction) * value2));
+
 #endif
       bp++; // next audio data
       mp++; // next modulation data
@@ -149,7 +158,25 @@ void AudioEffectModulatedDelay::update(void)
   }
 }
 
-void AudioEffectModulatedDelay::setDelay(float milliseconds)
+float AudioEffectModulatedDelay::offset(float offset_value)
 {
-  _delay_length = min(AUDIO_SAMPLE_RATE * milliseconds / 500, _max_delay_length);
+  uint16_t offset_frames = (offset_value / 1000) * AUDIO_SAMPLE_RATE;
+  if (offset_frames > _delay_length * MODULATION_MAX_FACTOR)
+    _delay_offset = _delay_length * MODULATION_MAX_FACTOR;
+  else if (offset_frames <= _delay_length * (1 - MODULATION_MAX_FACTOR))
+    _delay_offset = _delay_length * (1 - MODULATION_MAX_FACTOR);
+  else
+    _delay_offset = offset_frames;
+
+  return (offset_frames / AUDIO_SAMPLE_RATE * 1000);
+}
+
+void AudioEffectModulatedDelay::intensity(float intensity_value)
+{
+  if (intensity_value > 1.0)
+    intensity_value = 1.0;
+  else if (intensity_value < 0.0)
+    intensity_value = 0.0;
+
+  _modulation_intensity = intensity_value * (1 - MODULATION_MAX_FACTOR) * 2 * _delay_length;
 }

effect_modulated_delay.h

@@ -28,6 +28,8 @@
 #include "AudioStream.h"
 #include "config.h"
 
+#define MODULATION_MAX_FACTOR 0.75
+
 /*************************************************************************/
 //                A u d i o E f f e c t M o d u l a t e d D e l a y
 // Written by Pete (El Supremo) Jan 2014
@@ -44,14 +46,21 @@ class AudioEffectModulatedDelay :
 
     boolean begin(short *delayline, int delay_length);
     virtual void update(void);
-    virtual void setDelay(float milliseconds);
+    virtual float offset(float offset_value);
+    virtual void intensity(float intensity_value);
 
   private:
     audio_block_t *inputQueueArray[2];
     int16_t *_delayline;
     uint16_t _circ_idx;
-    uint16_t _max_delay_length;
+    uint16_t _delay_offset;
+    uint16_t _modulation_intensity;
     uint16_t _delay_length;
+#ifdef CHORUS_INTERPOLATION_MODE
+    float x[CHORUS_INTERPOLATION_WINDOW_SIZE];
+    float y[CHORUS_INTERPOLATION_WINDOW_SIZE];
+    Spline* spline;
+#endif
 };
 
 #endif

mdaEPiano.cpp

@@ -57,7 +57,7 @@ mdaEPiano::mdaEPiano() // mdaEPiano::mdaEPiano(audioMasterCallback audioMaster)
   setPanLFO(0.650f);
   setVelocitySense(0.250f);
   setStereo(0.500f);
-  setMaxPolyphony(1.0f);
+  setMaxPolyphony(NVOICES);
   setTune(0.500f);
   setDetune(0.146f);
   setOverdrive(0.000f);
@@ -232,6 +232,10 @@ void mdaEPiano::setStereo(float value)
 
 void mdaEPiano::setMaxPolyphony(uint8_t value)
 {
+  if (value > NVOICES)
+    value = NVOICES;
+  if (value <= 0)
+    value = 1;
   max_polyphony = value;
 }