diff --git a/src/RowBase.cpp b/src/RowBase.cpp
index 75acab9..d2391ab 100644
--- a/src/RowBase.cpp
+++ b/src/RowBase.cpp
@@ -29,7 +29,7 @@ Polling I2C may slow the scan rate enough so that no additional delay is needed:
     const unsigned int Row::DELAY_MICROSECONDS = 0;
 
 Slow-scan trick for debug messages that print too fast and not aligned, add this to sketch loop():
-    delay(1000);
+    delay(500);
     Keyboard.println("");
 That way debug messages are printed at a managable rate, and each scan starts a new line.
 */
@@ -41,6 +41,7 @@ void RowBase::wait()
 /*
 pressRelease() calls key's press() or release() function if it was pressed or released.
 Both parameters are bitwise.
+rowEnd bit marks positioned immediatly after last key of row.
 */
 void RowBase::pressRelease(const uint16_t rowEnd, const uint8_t debouncedChanged)
 {
diff --git a/src/RowScanner_Arduino.cpp b/src/RowScanner_Arduino.cpp
index a31e4e8..4421a33 100644
--- a/src/RowScanner_Arduino.cpp
+++ b/src/RowScanner_Arduino.cpp
@@ -2,11 +2,15 @@
 
 /*
 Strobes the row and reads the columns.
+Sets rowEnd and returns rowState.
+rowEnd is a bitwise row mask, one col per bit, where active col bit is 1.
+At end of function, 1 bit marks place immediatly after last key of row.
+rowEnd is a larger type than portMask so that it can not overflow.
 */
 uint8_t RowScanner_Arduino::scan(uint16_t& rowEnd)
 {
     uint8_t rowState = 0;
-    uint8_t col = 1;
+    rowEnd = 1;
 
     //strobe row on
     if (activeHigh)
@@ -17,16 +21,16 @@ uint8_t RowScanner_Arduino::scan(uint16_t& rowEnd)
     {
         digitalWrite(strobePin, LOW);
     }
-    delayMicroseconds(3);  //time to stablize voltage
+    delayMicroseconds(3);                       //time to stablize voltage
 
     //read all the column ports
     for (uint8_t i=0; i < READ_PIN_COUNT; i++)
     {
         if ( digitalRead(readPins[i]) == activeHigh )
         {
-            rowState |= col;
+            rowState |= rowEnd;
         }
-        col <<= 1;
+        rowEnd <<= 1;
     }
 
     //strobe row off
@@ -38,7 +42,6 @@ uint8_t RowScanner_Arduino::scan(uint16_t& rowEnd)
     {
         digitalWrite(strobePin, HIGH);
     }
-   
-    rowEnd = col;
+
     return rowState;
 }
diff --git a/src/RowScanner_Arduino.h b/src/RowScanner_Arduino.h
index 3403751..39f2779 100644
--- a/src/RowScanner_Arduino.h
+++ b/src/RowScanner_Arduino.h
@@ -5,19 +5,16 @@
 #include <RowScannerInterface.h>
 #include <RowPort.h>
 #include <ColPort.h>
-/* rowPin > strobePins[]
-replace port calls with
-  x pass 1: hard code pins for row0 and col6, init in setup()
-  x pass 2: readPins[] array
-    pass 3: move calls to IC classes - Strobe_uC, Read_uC
-    pass 4: add IC classes Strobe_MCP23018, Read_MCP23018 */
+
+/* RowScanner_Arduino class uses Arduino pin numbers (no port name).
+*/
 class RowScanner_Arduino : public RowScannerInterface
 {
     private:
         static const bool activeHigh;           //logic level of strobe pin: 0=activeLow, 1=activeHigh
-        const uint8_t strobePin;                 //Arduino pin number connected to this row
-        const uint8_t* readPins;                //array of read pins
-        const uint8_t READ_PIN_COUNT;//todo READ_PIN_COUNT
+        const uint8_t strobePin;                //Arduino pin number connected to this row
+        const uint8_t* readPins;                //array of read pin numbers
+        const uint8_t READ_PIN_COUNT;           //number of read pins
     public:
         RowScanner_Arduino(const uint8_t strobePin,
                 const uint8_t readPins[], const uint8_t READ_PIN_COUNT)
diff --git a/src/RowScanner_BitManipulation.cpp b/src/RowScanner_BitManipulation.cpp
index 2599d70..068c58c 100644
--- a/src/RowScanner_BitManipulation.cpp
+++ b/src/RowScanner_BitManipulation.cpp
@@ -37,14 +37,16 @@ uint8_t RowScanner_BitManipulation::scan(uint16_t& rowEnd)
 /*
 Copies column pins to rowState.  Unused column pins are not copied.
 Sets rowEnd and returns rowState.
-rowEnd is bitwise, where 1 bit corrsiponds to place immediatly after last key of row.
-rowEnd and rowMask are larger type than portMask so that they can not overflow.
+rowEnd is a bitwise row mask, one col per bit, where active col bit is 1.
+At end of function, 1 bit marks place immediatly after last key of row.
+rowEnd is a larger type than portMask so that it can not overflow.
 */
 uint8_t RowScanner_BitManipulation::getRowState(uint16_t& rowEnd)
 {
-    uint16_t rowMask = 1;           //bitwise, one col per bit, active col bit is 1
     uint8_t rowState = 0;           //bitwise, one key per bit, 1 means key is pressed
 
+    rowEnd = 1;
+
     for (uint8_t i=0; i < colPortCount; i++)    //for each col port
     {
         //bitwise colPins, 1 means pin is connected to column
@@ -64,15 +66,13 @@ uint8_t RowScanner_BitManipulation::getRowState(uint16_t& rowEnd)
             {
                 if (portMask & ~colPortState)   //if pin detected a key press
                 {
-                    rowState |= rowMask;        //set rowState bit for that key
+                    rowState |= rowEnd;         //set rowState bit for that key
                 }
 
-                rowMask <<= 1;                  //shift rowMask to next key
+                rowEnd <<= 1;                   //shift rowEnd to next key
             }
         }
     }
 
-    rowEnd = rowMask;
-
     return rowState;
 }
diff --git a/src/RowScanner_BitManipulation.h b/src/RowScanner_BitManipulation.h
index 3db523d..f719505 100644
--- a/src/RowScanner_BitManipulation.h
+++ b/src/RowScanner_BitManipulation.h
@@ -6,6 +6,8 @@
 #include <RowPort.h>
 #include <ColPort.h>
 
+/* RowScanner_BitManipulation uses bit manipulation to read all pins of one port.
+*/
 class RowScanner_BitManipulation : public RowScannerInterface
 {
     private: