Add ability to change response curve of volume CV and volume pot

stereo_mix/makefile

@@ -32,6 +32,7 @@ FAMILY            = f0xx
 #APPLICATION       = true
 #BOOTLOADER        = midi2cv_bootloader
 OPTIMIZE          = TRUE
+OPTIMIZE_FLAG     = 1
 # Preferred upload command
 UPLOAD_COMMAND  = upload_jtag
 

stereo_mix/processor.cc

@@ -1,10 +1,12 @@
 #include "processor.h"
 #include "stmlib/stmlib.h"
+#include "stmlib/utils/dsp.h"
 #include <math.h>
 
 using namespace stereo_mix;
+using namespace stmlib;
 
-const int kVolumeFilterValue = 4095;
+const int kVolumeFilterValue = 65535;
 
 void Processor::Process(int16_t cvs[], uint16_t* outs)
 {
@@ -16,28 +18,33 @@ void Processor::Process(int16_t cvs[], uint16_t* outs)
   int16_t pan_cv = cvs[0] >> (16 - 12);
   int16_t vol_cv = cvs[1] >> (16 - 12);
   int32_t pan = pan_pot + pan_cv;
-  int32_t vol = vol_pot + vol_cv;
+  int32_t lin = volume_offset + (cvs[1] * 2);
-  CONSTRAIN(pan, 0, (1 << 12) - 1);
+  CONSTRAIN(lin, 0, 65535);
-  CONSTRAIN(vol, 0, (1 << 12) - 1);
+  lin *= !mute;
+  linear_vol = lin;
 
-  if (mute) {
+  uint16_t vol_pot_exp = lut_linear_to_exp[vol_pot];
-    vol = 0;
+  uint16_t vol_pot_log = 65535 - lut_linear_to_exp[LUT_LINEAR_TO_EXP_SIZE - 1 - vol_pot];
-  }
 
-  if (vol > previous_vol + kVolumeFilterValue) {
+  vol_pot = Mix(vol_pot_exp, vol_pot_log, log_exp_mix_pot);
-    vol = previous_vol + kVolumeFilterValue;
-  } else if (vol < previous_vol - kVolumeFilterValue) {
-    vol = previous_vol - kVolumeFilterValue;
-  }
 
-  CONSTRAIN(pan, 0, (1 << 12) - 1);
+  uint16_t vol_cv_absu16 = abs(vol_cv) << 1;
-  CONSTRAIN(vol, 0, (1 << 12) - 1);
+  uint16_t vol_cv_exp = lut_linear_to_exp[vol_cv_absu16];
+  uint16_t vol_cv_log = 65535 - lut_linear_to_exp[LUT_LINEAR_TO_EXP_SIZE - 1 - vol_cv_absu16];
+  uint16_t vol_cv_pre = Mix(vol_cv_exp, vol_cv_log, log_exp_mix_cv);
+  int32_t vol = vol_pot;
+  vol += vol_cv > 0 ? vol_cv_pre : -vol_cv_pre;
+
+  vol *= !mute;
+
+  CONSTRAIN(pan, 0, (1 << 16) - 1);
+  CONSTRAIN(vol, 0, (1 << 16) - 1);
 
   previous_vol = vol;
 
   // leds.set_intensity(i, vol >> 4);
-  value_l = (lut_left_sin_pan[pan] * lut_linear_to_exp[vol]) >> 16;
+  value_l = (lut_left_sin_pan[pan] * vol) >> 16;
-  value_r = (lut_right_cos_pan[pan] * lut_linear_to_exp[vol]) >> 16;
+  value_r = (lut_right_cos_pan[pan] * vol) >> 16;
 
   outs[0] = value_r;
   outs[1] = value_l;

stereo_mix/processor.h

@@ -22,13 +22,18 @@ class Processor {
     mute = m;
   }
 
-  uint16_t previous_volume() {
+  uint16_t linear_volume() {
-    return previous_vol;
+    return linear_vol;
   }
 
   private:
   uint16_t volume_offset = 0;
   int16_t pan_offset = 0;
   uint16_t previous_vol;
+  uint16_t linear_vol;
+
+  uint16_t log_exp_mix_cv  = 32767; // -> linear
+  uint16_t log_exp_mix_pot = 0;
+
   bool mute = false;
 };

stereo_mix/resources/lookup_tables.py

@@ -1,4 +1,7 @@
 import numpy as np
+import matplotlib
+import matplotlib.pyplot as plt
+
 lookup_tables_u16 = []
 lookup_tables_u8 = []
 
@@ -7,11 +10,22 @@ OUTPUT_RESOLUTION = 2 ** 16 - 1
 
 # linear to exponential conversion
 
-values = np.linspace(0, 1, num=ADC_RESOLUTION)
+space = np.linspace(0, 1, num=ADC_RESOLUTION)
-values = np.power(values, 2) * OUTPUT_RESOLUTION
+values = np.power(space, 2) * OUTPUT_RESOLUTION
 
 lookup_tables_u16.append(('linear_to_exp', values))
 
+fig, ax = plt.subplots()
+ax.plot(space, values)
+other_values = OUTPUT_RESOLUTION - np.flip(values)
+ax.plot(space, OUTPUT_RESOLUTION - (np.flip(values)))
+ax.plot(space, values / 2 + other_values / 2)
+
+ax.set(xlabel='space', ylabel='values')
+ax.grid()
+
+#plt.show()
+
 
 # Left pan Lookup table
 
@@ -34,4 +48,3 @@ max_out = 511
 input_vals = np.linspace(0, max_in, num=max_in + 1)
 gamma_correction = ((input_vals / max_in) ** gamma) * max_out + 0.5
 lookup_tables_u16.append(('led_gamma', np.floor(gamma_correction)))
-

stereo_mix/resources/resources.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python2.5
+#!/usr/bin/python
 #
 # Copyright 2016 Emilie Gillet.
 #

stereo_mix/stereo_mix.cc

@@ -145,7 +145,7 @@ void Init(void)
   HAL_NVIC_EnableIRQ(TIM6_IRQn);
   htim6.Init.Prescaler = 64;
   htim6.Init.CounterMode = TIM_COUNTERMODE_UP;
-  htim6.Init.Period = 96; //128; //256; //512;
+  htim6.Init.Period = 96; // 512 without optimize
   htim6.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
   htim6.Init.RepetitionCounter = 0;
   HAL_TIM_Base_Init(&htim6);

stereo_mix/ui.cc

@@ -113,7 +113,7 @@ void UI::TaskDrawLeds()
         leds->set_blinking(i, pan_pots[i] - 32767 < 0);
       } else {
         // show volume if not muted
-        leds->set_intensity(i, processors[i].previous_volume() >> (4));
+        leds->set_intensity(i, processors[i].linear_volume() >> (8));
         leds->set_blinking(i, false);
       }
     }