From afae00a6544de9f80bb8e3e69040f34938109e9b Mon Sep 17 00:00:00 2001
From: Christian Speckner <christian.speckner@mayflower.de>
Date: Thu, 8 Dec 2016 00:37:12 +0100
Subject: [PATCH] Fix analog I/O:

    * Premature optimization killed the cat --- approximated exponentioal does
      not converge fast enough, replace with real thing
    * Make sure that the readout circuit is updated before read
---
 src/emucore/tia/core_6502ts/PaddleReader.cxx | 12 +-----
 src/emucore/tia/core_6502ts/TIA.cxx          | 41 ++++++++++++++------
 src/emucore/tia/core_6502ts/TIA.hxx          |  2 +-
 3 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/src/emucore/tia/core_6502ts/PaddleReader.cxx b/src/emucore/tia/core_6502ts/PaddleReader.cxx
index 8ec60e91c..111b557fe 100644
--- a/src/emucore/tia/core_6502ts/PaddleReader.cxx
+++ b/src/emucore/tia/core_6502ts/PaddleReader.cxx
@@ -21,16 +21,6 @@
 
 #include "PaddleReader.hxx"
 
-
-static double expApprox(double x)
-{
-  double  x2 = x  * x / 2,
-          x3 = x2 * x / 3,
-          x4 = x3 * x / 4;
-
-  return 1 + x + x2 + x3 + x4;
-}
-
 static constexpr double
   C = 68e-9,
   RPOT = 1e6,
@@ -112,7 +102,7 @@ void PaddleReader::updateCharge(double timestamp)
   if (myIsDumped) return;
 
   myU = USUPP * (1 - (1 - myU / USUPP) *
-    expApprox(-(timestamp - myTimestamp) / (myValue * RPOT + R0) / C / myClockFreq));
+    exp(-(timestamp - myTimestamp) / (myValue * RPOT + R0) / C / myClockFreq));
 
   myTimestamp = timestamp;
 }
diff --git a/src/emucore/tia/core_6502ts/TIA.cxx b/src/emucore/tia/core_6502ts/TIA.cxx
index 0d21c5f7d..9bc261fc6 100644
--- a/src/emucore/tia/core_6502ts/TIA.cxx
+++ b/src/emucore/tia/core_6502ts/TIA.cxx
@@ -72,7 +72,9 @@ TIA::TIA(Console& console, Sound& sound, Settings& settings)
   myFrameManager.setHandlers(
     [this] () {
       myCurrentFrameBuffer.swap(myPreviousFrameBuffer);
-      updatePaddles();
+
+      for (uInt8 i = 0; i < 4; i++)
+        updatePaddle(i);
     },
     [this] () {
       mySystem->m6502().stop();
@@ -300,18 +302,22 @@ uInt8 TIA::peek(uInt16 address)
       break;
 
     case INPT0:
+      updatePaddle(0);
       result = myPaddleReaders[0].inpt(myTimestamp);
       break;
 
     case INPT1:
+      updatePaddle(1);
       result = myPaddleReaders[1].inpt(myTimestamp);
       break;
 
     case INPT2:
+      updatePaddle(2);
       result = myPaddleReaders[2].inpt(myTimestamp);
       break;
 
     case INPT3:
+      updatePaddle(3);
       result = myPaddleReaders[3].inpt(myTimestamp);
       break;
 
@@ -1194,20 +1200,33 @@ void TIA::delayedWrite(uInt8 address, uInt8 value)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void TIA::updatePaddles()
+void TIA::updatePaddle(uInt8 idx)
 {
   static constexpr double MAX_RESISTANCE = 1400000;
 
-  TvMode tvMode = myFrameManager.tvMode();
-  Int32 resistances[] = {
-    myConsole.leftController().read(Controller::Nine),
-    myConsole.leftController().read(Controller::Five),
-    myConsole.rightController().read(Controller::Nine),
-    myConsole.rightController().read(Controller::Five),
-  };
+  Int32 resistance;
+  switch (idx) {
+    case 0:
+      resistance = myConsole.leftController().read(Controller::Nine);
+      break;
 
-  for (uInt8 i = 0; i < 4; i++)
-    myPaddleReaders[i].update(double(resistances[i]) / MAX_RESISTANCE, myTimestamp, tvMode);
+    case 1:
+      resistance = myConsole.leftController().read(Controller::Five);
+      break;
+
+    case 2:
+      resistance = myConsole.rightController().read(Controller::Nine);
+      break;
+
+    case 3:
+      resistance = myConsole.rightController().read(Controller::Five);
+      break;
+
+    default:
+      throw runtime_error("invalid paddle index");
+  }
+
+  myPaddleReaders[idx].update(double(resistance) / MAX_RESISTANCE, myTimestamp, myFrameManager.tvMode());
 }
 
 } // namespace TIA6502tsCore
diff --git a/src/emucore/tia/core_6502ts/TIA.hxx b/src/emucore/tia/core_6502ts/TIA.hxx
index 544aab00a..6c71f139a 100644
--- a/src/emucore/tia/core_6502ts/TIA.hxx
+++ b/src/emucore/tia/core_6502ts/TIA.hxx
@@ -244,7 +244,7 @@ class TIA : public AbstractTIA
 
     void delayedWrite(uInt8 address, uInt8 value);
 
-    void updatePaddles();
+    void updatePaddle(uInt8 idx);
 
   private: