diff --git a/examples/debounce_unit_test.cpp b/examples/debounce_unit_test.cpp
index d0eaee6..9090fe1 100644
--- a/examples/debounce_unit_test.cpp
+++ b/examples/debounce_unit_test.cpp
@@ -12,14 +12,18 @@ to run test:
 
 uint8_t samples[SAMPLE_COUNT];                  //bitwise, one bit per key, most recent readings
 uint8_t samplesIndex = 0;                       //samples[] current write index
-uint8_t debounced = 0;                          //bitwise, one bit per key
+uint8_t previousDebounced = 0;                  //bitwise, one bit per key
 
-uint8_t debounce(const uint8_t rowState)
+uint8_t isFallingEdge;                          //1 means falling edge
+uint8_t isRisingEdge;                           //1 means rising edge
+
+uint8_t debounce(const uint8_t rowState, uint8_t& debounced)
 {
+    uint8_t debouncedChanged;                   //bitwise
     uint8_t all_1 = ~0;                         //bitwise
     uint8_t all_0 = 0;                          //bitwise
 
-    //delayMicroseconds(DELAY_MICROSECONDS);    //delay between Row scans to debounce key
+    //delayMicroseconds(DELAY_MICROSECONDS);      //delay between Row scans to debounce key
 
     samples[samplesIndex] = rowState;           //insert rowState into samples[] ring buffer
 
@@ -35,42 +39,82 @@ uint8_t debounce(const uint8_t rowState)
     }
 
     // update newDebounce if all the samples agree with one another
-    // if all samples=1 then newDebounced=1
-    //     elseif all samples=0 then newDebounced=0
-    //         else newDebounced=debounced i.e. no change
-    //return all_1 | (all_0 & debounced);
-    debounced = all_1 | (all_0 & debounced);
-    return debounced;
+    // if all samples=1 then debounced=1
+    //     elseif all samples=0 then debounced=0
+    //         else debounced=previousDebounced i.e. no change
+    debounced = all_1 | (all_0 & previousDebounced);
+
+    debouncedChanged = debounced xor previousDebounced;
+    previousDebounced = debounced;
+    return debouncedChanged;
+}
+
+void pressRelease(const uint8_t debouncedChanged)
+{
+    //bit=1 if last debounced changed from 1 to 0, else bit=0
+    isFallingEdge = debouncedChanged & ~previousDebounced;
+
+    //bit=1 if last debounced changed from 0 to 1, else bit=0
+    isRisingEdge = debouncedChanged & previousDebounced;
 }
 
 int main()
 {
     //Test input and output only shows first bit of each byte.
-    const uint8_t pressed[] = {1,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,0,0,0};
-    const uint8_t bouncy[]  = {1,0,0,0,0,1,0,0,1,1,1,1,0,1,1,1,1,0,0,0,0};
+    const uint8_t pressed[]        = {1,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,0,0,0};
+    const uint8_t bouncy[]         = {1,0,0,0,0,1,0,0,1,1,1,1,0,1,1,1,1,0,0,0,0};
+    const uint8_t expectDebounced[]= {0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0};
     const uint8_t SCAN_COUNT = sizeof(bouncy)/sizeof(*bouncy);
     uint8_t i;
-    uint8_t newDebounced;
+    uint8_t debounced;                          //1 means pressed, 0 means released
+    uint8_t debouncedChanged;                   //1 means debounced changed
 
-    std::cout << "button pressed:   ";
+    std::cout << "button pressed:            ";
     for (i=0; i<SCAN_COUNT; i++)
     {
         std::cout << (int)pressed[i];
     }
     std::cout << std::endl;
 
-    std::cout << "bouncy signal:    ";
+    std::cout << "bouncy signal:             ";
     for (i=0; i<SCAN_COUNT; i++)
     {
         std::cout << (int)bouncy[i];
     }
     std::cout << std::endl;
 
-    std::cout << "debounced signal: ";
+    std::cout << "debounced signal:          ";
     for (i=0; i<SCAN_COUNT; i++)
     {
-        newDebounced = debounce(bouncy[i]);
-        std::cout << (int)newDebounced;
+        debouncedChanged = debounce(bouncy[i], debounced);
+        //pressRelease(debouncedChanged);
+        std::cout << (int)debounced;
+    }
+    std::cout << std::endl;
+
+    std::cout << "expected debounced signal: ";
+    for (i=0; i<SCAN_COUNT; i++)
+    {
+        std::cout << (int)expectDebounced[i];
+    }
+    std::cout << std::endl;
+
+
+    std::cout << "isFallingEdge:             ";
+    for (i=0; i<SCAN_COUNT; i++)
+    {
+        debouncedChanged = debounce(bouncy[i], debounced);
+        pressRelease(debouncedChanged);
+        std::cout << (int)isFallingEdge;
+    }
+    std::cout << std::endl;
+
+    std::cout << "isRisingEdge:              ";
+    for (i=0; i<SCAN_COUNT; i++)
+    {
+        debouncedChanged = debounce(bouncy[i], debounced);
+        pressRelease(debouncedChanged);
+        std::cout << (int)isRisingEdge;
     }
     std::cout << std::endl;
 }
diff --git a/src/RowBase.cpp b/src/RowBase.cpp
index bf17f48..b8e84d5 100644
--- a/src/RowBase.cpp
+++ b/src/RowBase.cpp
@@ -7,15 +7,13 @@ void RowBase::process(const bool activeHigh)
     //these variables are all bitwise, one bit per key
     uint8_t rowState;                           //1 means pressed, 0 means released
     uint16_t rowEnd;                            //1 bit marks positioned after last key of row
-    uint8_t debounced;                       //1 means pressed, 0 means released
-    uint8_t isFallingEdge;                      //1 means falling edge
-    uint8_t isRisingEdge;                       //1 means rising edge
+    uint8_t debounced;                          //1 means pressed, 0 means released
+    uint8_t debouncedChanged;                   //1 means debounced changed
 
     scan(activeHigh);                           //save column-port-pin values to portState
     rowState = getRowState(rowEnd, activeHigh);
-    debounced = debounce(rowState);
-    detectEdge(debounced, isFallingEdge, isRisingEdge);
-    pressRelease(rowEnd, isFallingEdge, isRisingEdge);
+    debouncedChanged = debounce(rowState, debounced);
+    pressRelease(rowEnd, debouncedChanged);
 }
 
 /*
@@ -95,32 +93,21 @@ uint8_t RowBase::getRowState(uint16_t& rowEnd, const bool activeHigh)
 }
 
 /*
-Computes isFallingEdge and isRisingEdge.
-All 3 parameters are bitwise.
+pressRelease() calls key's press() or release() function if it was pressed or released.
+Both parameters are bitwise.
 */
-void RowBase::detectEdge(uint8_t debounced, uint8_t& isFallingEdge, uint8_t& isRisingEdge)
+void RowBase::pressRelease(const uint16_t rowEnd, const uint8_t debouncedChanged)
 {
-    uint8_t debouncedChanged;                   //bitwise
-
-    debouncedChanged = debounced xor previousDebounced;
-    previousDebounced = debounced;
+    uint8_t isFallingEdge;                      //1 means falling edge
+    uint8_t isRisingEdge;                       //1 means rising edge
+    uint8_t rowMask;                            //bitwise, active col bit is 1
+    uint8_t col;                                //index for ptrsKeys[col] array
 
     //bit=1 if last debounced changed from 1 to 0, else bit=0
     isFallingEdge = debouncedChanged & ~previousDebounced;
 
     //bit=1 if last debounced changed from 0 to 1, else bit=0
     isRisingEdge = debouncedChanged & previousDebounced;
-}
-
-/*
-calls key's press() or release() function if it was pressed or released.
-All 3 parameters are bitwise.
-*/
-void RowBase::pressRelease(const uint16_t rowEnd, const uint8_t isFallingEdge,
-                       const uint8_t isRisingEdge)
-{
-    uint8_t rowMask;                            //bitwise, active col bit is 1
-    uint8_t col;                                //index for ptrsKeys[col] array
 
     for (rowMask=1, col=0; rowMask<rowEnd; rowMask<<=1, col++) //for each key in row
     {
diff --git a/src/RowBase.h b/src/RowBase.h
index 98ab1ff..dbbf601 100644
--- a/src/RowBase.h
+++ b/src/RowBase.h
@@ -57,10 +57,9 @@ class RowBase
 
         void scan(const bool activeHigh);
         uint8_t getRowState(uint16_t& rowEnd, const bool activeHigh);
-        virtual uint8_t debounce(const uint8_t rowState)=0; //debouncer and I2C error correction
-        void detectEdge(uint8_t debounced, uint8_t& isFallingEdge, uint8_t& isRisingEdge);
-        void pressRelease(const uint16_t rowEnd,
-                const uint8_t isFallingEdge, const uint8_t isRisingEdge);
+        virtual uint8_t debounce(const uint8_t rowState, uint8_t& debounced)=0;
+        //void detectEdge(uint8_t debounced, uint8_t& isFallingEdge, uint8_t& isRisingEdge);
+        void pressRelease(const uint16_t rowEnd, const uint8_t debouncedChanged);
         virtual void keyWasPressed();
     protected:
         uint8_t previousDebounced;              //bitwise, one bit per key