Make DAC leakage adjustable (#10)

src/Dac.cpp

@@ -69,7 +69,7 @@ double Dac::getOutput(unsigned int input, bool saturate) const
     return dacValue;
 }
 
-void Dac::kinkedDac(ChipModel chipModel)
+void Dac::kinkedDac(ChipModel chipModel, double leakLevel)
 {
     constexpr double R_INFINITY = 1e6;
 
@@ -79,7 +79,7 @@ void Dac::kinkedDac(ChipModel chipModel)
     // 6581 DACs are not terminated by a 2R resistor
     const bool term = chipModel == CSG8580;
 
-    leakage = chipModel == MOS6581 ? MOSFET_LEAKAGE_6581 : MOSFET_LEAKAGE_8580;
+    leakage = leakLevel * (chipModel == MOS6581 ? MOSFET_LEAKAGE_6581 : MOSFET_LEAKAGE_8580);
 
     double Vsum = 0.;
 

src/Dac.h

@@ -108,8 +108,9 @@ class Dac
      * Build DAC model for specific chip.
      *
      * @param chipModel 6581 or 8580
+     * @param leakLevel the level of the transistor leakage
      */
-    void kinkedDac(ChipModel chipModel);
+    void kinkedDac(ChipModel chipModel, double leakLevel=1.0);
 
     /**
      * Get the Vo output for a  given combination of input bits.

src/SID.cpp

@@ -24,6 +24,7 @@
 
 #include "SID.h"
 
+#include <algorithm>
 #include <limits>
 
 #include "array.h"
@@ -142,6 +143,7 @@ SID::SID() :
     filter8580(new Filter8580()),
     resampler(nullptr),
     cws(AVERAGE),
+    dacLeakage(1.0),
     p(new Params)
 {
     voice[0].setOtherVoices(voice[2], voice[1]);
@@ -252,7 +254,7 @@ void SID::setChipModel(ChipModel new_model)
     // calculate envelope DAC table
     {
         Dac dacBuilder(ENV_DAC_BITS);
-        dacBuilder.kinkedDac(model);
+        dacBuilder.kinkedDac(model, dacLeakage);
 
         for (unsigned int i = 0; i < (1 << ENV_DAC_BITS); i++)
         {
@@ -265,7 +267,7 @@ void SID::setChipModel(ChipModel new_model)
 
     {
         Dac dacBuilder(OSC_DAC_BITS);
-        dacBuilder.kinkedDac(model);
+        dacBuilder.kinkedDac(model, dacLeakage);
 
         //const double offset = dacBuilder.getOutput(is6581 ? OFFSET_6581 : OFFSET_8580);
         const double offset = dacBuilder.getOutput(is6581 ? OFFSET_6581 : 0x7ff, is6581);
@@ -614,4 +616,15 @@ void SID::setPaddle(uint8_t x, uint8_t y)
     paddleY = y;
 }
 
+
+void SID::setDacLeakage(double level)
+{
+#ifdef HAVE_CXX17
+     dacLeakage = std::clamp(level, 0.0, 1.0);
+#else
+     dacLeakage = std::max(std::min(level, 1.0), 0.0);
+#endif
+    setChipModel(model);
+}
+
 } // namespace reSIDfp

src/SID.h

@@ -104,6 +104,9 @@ class SID
     /// Currently selected combined waveforms strength.
     CombinedWaveforms cws;
 
+    // Dac leakage
+    double dacLeakage;
+
     /// Last written value
     uint8_t busValue;
 
@@ -358,6 +361,11 @@ class SID
      * Set paddle coordinates.
      */
     void setPaddle(uint8_t x, uint8_t y);
+
+    /*
+     * Set the DAC leakage level.
+     */
+    void setDacLeakage(double level);
 };
 
 } // namespace reSIDfp

src/State.cpp

@@ -84,6 +84,7 @@ int State::saveState(SID &s, char* buffer, int size)
         state.env3[i] = envelope->env3;
     }
 
+    state.dacLeakage = s.dacLeakage;
     state.bus_value = s.busValue;
     state.bus_value_ttl = s.busValueTtl;
     state.nextVoiceSync = s.nextVoiceSync;
@@ -194,6 +195,7 @@ void State::restoreState(SID &s, char* buffer, int size)
     State state;
     std::memcpy(&state, buffer, cnt);
 
+    s.dacLeakage = state.dacLeakage;
     s.busValue = state.bus_value;
     s.busValueTtl = state.bus_value_ttl;
     s.nextVoiceSync = state.nextVoiceSync;

src/State.h

@@ -65,6 +65,7 @@ struct State
     unsigned int nextVoiceSync;
     ChipModel model;
     CombinedWaveforms cws;
+    double dacLeakage;
     uint8_t bus_value;
     uint8_t paddle_x;
     uint8_t paddle_y;

src/residfp/residfp.cpp

@@ -174,3 +174,8 @@ void residfp::restoreState(char* buffer, int size)
 {
     State::restoreState(sid, buffer, size);
 }
+
+void residfp::setDacLeakage(double level)
+{
+    sid.setDacLeakage(level);
+}

src/residfp/residfp.h

@@ -280,6 +280,16 @@ class RESIDFP_EXTERN residfp
      * @since 1.1
      */
     void restoreState(char* buffer, int size);
+
+    /**
+     * Set the DAC leakage level.
+     * Affects the envelope and waveforms.
+     *
+     * @param level the leakage level, between 0 (no leakage) and 1
+     *
+     * @since 1.2
+     */
+    void setDacLeakage(double level);
 };
 
 }