scroll wheel is now done with a stochastic algorithm to make up for the inherent noise in the phototransistor

firmware/production/Scroller.cpp

@@ -17,6 +17,9 @@
  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#if defined(ARDUINO) && ARDUINO >= 100
+#include "Arduino.h"
+#endif
 #include "Scroller.h"
 
 Scroller::Scroller(void) {
@@ -25,15 +28,29 @@ Scroller::Scroller(void) {
   hilof = false;
   lowA = 1023;
   highA = 0;
+  cLowA = false;
+  cHighA = false;
+  lowIndexA = 0;
+  highIndexA = 0;
+  lowOverflowA = false;
+  highOverflowA = false;
   lowB = 1023;
   highB = 0;
+  cLowB = false;
+  cHighB = false;
+  lowIndexB = 0;
+  highIndexB = 0;
+  lowOverflowB = false;
+  highOverflowB = false;
   scrollThresholdA = 0;
   scrollThresholdB = 0;
 }
 
 int Scroller::scroll(int curA, int curB) {
-  calculateThresholdA(curA);
-  calculateThresholdB(curB);
+  if (lowOverflowA == false || highOverflowA == false)
+    calculateThresholdA(curA);
+  if (lowOverflowB == false || highOverflowB == false)
+    calculateThresholdB(curB);
 
   bool LO = false;
   bool HI = true;
@@ -109,36 +126,147 @@ int Scroller::scroll(int curA, int curB) {
   return ret;
 }
 
-int Scroller::getScrollThresholdA(void) {
-  return scrollThresholdA;
-}
-
-int Scroller::al(void) {
-  return lowA;
-}
-
-int Scroller::ah(void) {
-  return highA;
-}
-
-int Scroller::getScrollThresholdB(void) {
-  return scrollThresholdB;
-}
-
 int Scroller::calculateThresholdA(int curA) {
-  if (curA < lowA)
-    lowA = curA;
-  else if (curA > highA)
-    highA = curA;
-
-  scrollThresholdA = ((highA - lowA) / 3) + lowA;
+  scrollThresholdA = calculateThreshold(curA, lowA, highA,
+    cLowA, cHighA, arLowA, arHighA, lowIndexA, highIndexA,
+    lowOverflowA, highOverflowA);
 }
 
 int Scroller::calculateThresholdB(int curB) {
-  if (curB < lowB)
-    lowB = curB;
-  else if (curB > highB)
-    highB = curB;
-
-  scrollThresholdB = ((highB - lowB) / 3) + lowB;
+  scrollThresholdB = calculateThreshold(curB, lowB, highB,
+    cLowB, cHighB, arLowB, arHighB, lowIndexB, highIndexB,
+    lowOverflowB, highOverflowB);
+}
+
+int Scroller::calculateThreshold(int cur, int &low, int &high,
+    bool &cLow, bool &cHigh, int arLow[], int arHigh[],
+    int &lowIndex, int &highIndex, bool &lowOverflow,
+    bool &highOverflow) {
+
+  if (cur < low)
+    low = cur;
+  if (cur > high)
+    high = cur;
+
+  int curThresh = thresholdEquation(low, high);
+  int range = high - low;
+
+  // The range is enforced to be over a certain limit because noise
+  // can cause erroneous readings, making these calculations unstable.
+  if (range >= THRESH_RANGE_LIM) {
+    if (cur < curThresh) {
+      if (cHigh == true) {
+        // We were just high, and now we crossed to low.
+        // high reflects a sample of a high reading.
+        arHigh[highIndex] = high;
+        incrementIndex(highIndex, highOverflow);
+        int midpoint = ((high - low) / 2) + low;
+        low = midpoint;
+        high = midpoint;
+        cLow = false;
+        cHigh = false;
+      } else {
+        cLow = true;
+      }
+    } if (cur > curThresh) {
+      if (cLow == true) {
+        // We were just low, and now we crossed to high.
+        // low reflects a sample of a low reading.
+        arLow[lowIndex] = low;
+        incrementIndex(lowIndex, lowOverflow);
+        int midpoint = ((high - low) / 2) + low;
+        low = midpoint;
+        high = midpoint;
+        cLow = false;
+        cHigh = false;
+      } else {
+        cHigh = true;
+      }
+    }
+  }
+
+  int calcHigh = 0;
+  if (highOverflow == true) {
+    for (int i = 0; i < SCROLLER_AR_SIZE; i++) {
+      calcHigh += arHigh[i];
+    }
+    calcHigh = calcHigh / SCROLLER_AR_SIZE;
+  } else if (highIndex != 0) {
+    for (int i = 0; i < highIndex; i++) {
+      calcHigh += arHigh[i];
+    }
+    calcHigh = calcHigh / highIndex;
+  } else {
+    calcHigh = high;
+  }
+
+  int calcLow = 0;
+  if (lowOverflow == true) {
+    for (int i = 0; i < SCROLLER_AR_SIZE; i++) {
+      calcLow += arLow[i];
+    }
+    calcLow = calcLow / SCROLLER_AR_SIZE;
+  } else if (lowIndex != 0) {
+    for (int i = 0; i < lowIndex; i++) {
+      calcLow += arLow[i];
+    }
+    calcLow = calcLow / lowIndex;
+  } else {
+    calcLow = low;
+  }
+
+  return thresholdEquation(calcLow, calcHigh);
+}
+
+int Scroller::thresholdEquation(int lo, int hi) {
+  return ((hi - lo) / 3) + lo;
+}
+
+void Scroller::incrementIndex(int &index, bool &ovflw) {
+  if (index < SCROLLER_AR_SIZE - 1)
+    index++;
+  else {
+    index = 0;
+    ovflw = true;
+  }
+}
+
+void Scroller::debug(void) {
+  /*
+  Serial.print(F("lowA: "));
+  Serial.print(lowA);
+  Serial.print(F(", highA: "));
+  Serial.print(highA);
+  Serial.print(F(", cLowA: "));
+  Serial.print(cLowA ? "true" : "false");
+  Serial.print(F(", cHighA: "));
+  Serial.print(cHighA ? "true" : "false");
+  Serial.print(F(", lowIndexA: "));
+  Serial.print(lowIndexA);
+  Serial.print(F(", highIndexA: "));
+  Serial.print(highIndexA);
+  Serial.print(F(", lowOverflowA: "));
+  Serial.print(lowOverflowA ? "true" : "false");
+  Serial.print(F(", highOverflowA: "));
+  Serial.println(highOverflowA ? "true" : "false");
+
+  Serial.print(F("arLowA: "));
+  for (int i = 0; i < SCROLLER_AR_SIZE; i++) {
+    Serial.print(arLowA[i]);
+    Serial.print(F(","));
+  }
+  Serial.println(".");
+
+  Serial.print(F("arHighA: "));
+  for (int i = 0; i < SCROLLER_AR_SIZE; i++) {
+    Serial.print(arHighA[i]);
+    Serial.print(F(","));
+  }
+  Serial.println(".");
+  */
+  
+  Serial.print(F(", thB: "));
+  Serial.print(scrollThresholdB);
+  Serial.print(F(", thA: "));
+  Serial.print(scrollThresholdA);
 }

firmware/production/Scroller.h

@@ -17,30 +17,51 @@
  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#ifndef SCROLLER_AR_SIZE
+#define SCROLLER_AR_SIZE 40
+#endif
+
 #ifndef SCROLLER_h
 #define SCROLLER_h
 
 class Scroller {
   private:
+    const int THRESH_RANGE_LIM = 10;
     enum State { HIHI, HILO, LOLO, LOHI };
     State state;
     bool lohif;
     bool hilof;
     int lowA;
     int highA;
+    bool cLowA;
+    bool cHighA;
+    int lowIndexA;
+    int highIndexA;
+    bool lowOverflowA;
+    bool highOverflowA;
     int lowB;
     int highB;
+    bool cLowB;
+    bool cHighB;
+    int lowIndexB;
+    int highIndexB;
+    bool lowOverflowB;
+    bool highOverflowB;
     int scrollThresholdA;
     int scrollThresholdB;
+    int arLowA[SCROLLER_AR_SIZE];
+    int arHighA[SCROLLER_AR_SIZE];
+    int arLowB[SCROLLER_AR_SIZE];
+    int arHighB[SCROLLER_AR_SIZE];
     int calculateThresholdA(int);
     int calculateThresholdB(int);
+    int calculateThreshold(int, int&, int&, bool&, bool&, int*, int*, int&, int&, bool&, bool&);
+    int thresholdEquation(int, int);
+    void incrementIndex(int&, bool&);
   public:
     Scroller(void);
     int scroll(int, int);
-    int getScrollThresholdA(void);
-    int getScrollThresholdB(void);
-    int al(void);
-    int ah(void);
+    void debug(void);
 };
 
 #endif

firmware/production/production.ino

@@ -393,15 +393,14 @@ signed char moveWheel() {
   if (middleButtonPin == LOW) {
     return 0;
   }
-  
+
   lastScroll = micros();
-  
+
   int d1 = analogRead(OPT_ENC_PIN1);
   int d2 = analogRead(OPT_ENC_PIN2);
 
   if (debugMode) {
-    Serial.print(F("th: "));
-    Serial.print(scroller.getScrollThreshold());
+    scroller.debug();
     Serial.print(F(", d1: "));
     Serial.print(d1);
     Serial.print(F(", d2: "));