diff --git a/doc/keybrd_library_developer_guide.md b/doc/keybrd_library_developer_guide.md
index fca3ec1..0959c0c 100644
--- a/doc/keybrd_library_developer_guide.md
+++ b/doc/keybrd_library_developer_guide.md
@@ -204,16 +204,15 @@ Example Code_Layered class names:
 
 ## Style guide
 Following the style guide makes it easier for the next programmer to understand your code.
-* For class names, see above section "Class naming conventions"
-* For member names, use camelCase starting with lowercase letter.
+* For class names, see above section "Class naming conventions".
+* Member names use camelCase starting with lowercase letter.
 * Use constants rather than macros, except for header guards.
-* For constant names that could be macros, use ALL_CAPS_AND_UNDERSCORE.
-    * **ITEM_COUNT** is a constant number of items.
-    * **itemCount** is a variable number of items.
-* Use header guards CLASS_NAME_H.
-* Prefix pointer name with "ptr" e.g. ptrRow =  &row;
-* Name arrays using the plural of element name e.g. Row* const = ptrsRows { &row0,  &row1 };
-* Pass arrays using array notation rather than pointer notation.  Use
+* Global const names and static const names use ALL_CAPS_AND_UNDERSCORE.
+* Macros use ALL_CAPS_AND_UNDERSCORE and have _MACRO suffix e.g. SAMPLE_COUNT_MACRO
+* Header guards have _H suffix e.g. #ifndef FILE_NAME_H
+* Pointer names are prefixed with "ptr" e.g. ptrRow =  &row;
+* Arrays names use the plural of element name e.g. Row* const = ptrsRows { &row0,  &row1 };
+* Pass arrays using array notation rather than pointer notation:
 ```
         void printArray(char[] array);
     not
@@ -222,8 +221,8 @@ Following the style guide makes it easier for the next programmer to understand
 * In constructor's initialization list, use same names for fields and constructor parameters.
 * Do not use new or malloc (making memory leaks impossible).
 * Document class interface in .h file, above the class declaration.
-* Code should be self-documenting.  The only comments should be things that may need clarification.  A simple function with a good name needs no comment.
-* Code is automatically formated before being pushed to the keybrd repository.
+* Code should be self-documenting.  A simple function with a good name needs no comment.
+* Code is automatically formatted before being pushed to the keybrd repository.
   The [astyle_cpp](astyle_cpp) file specifies the format:
     * Allman style indentation
     * indent 4 spaces
diff --git a/examples/keybrd_shift_register/keybrd_shift_register.ino b/examples/keybrd_shift_register/keybrd_shift_register.ino
index f559269..fa3d8b4 100644
--- a/examples/keybrd_shift_register/keybrd_shift_register.ino
+++ b/examples/keybrd_shift_register/keybrd_shift_register.ino
@@ -17,7 +17,8 @@ Unused input pins are not grounded, so add this line to Scanner_ShiftRegs74HC165
 // ================= INCLUDES ==================
 #include <Debug.h>
 #include <ScanDelay.h>
-#include <LED_PinNumber.h>
+#include <LED_uC.h>
+#include <SPI.h>
 
 //Codes
 #include <Code_Sc.h>
@@ -25,7 +26,6 @@ Unused input pins are not grounded, so add this line to Scanner_ShiftRegs74HC165
 
 //Matrix
 #include <Row_uC.h>
-#include <SPI.h>
 #include <Row_ShiftRegisters.h>
 
 // =============== CONFIGURATION ===============
@@ -48,7 +48,7 @@ uint8_t readPins[] = {14, 15};
 uint8_t READ_PIN_COUNT = sizeof(readPins)/sizeof(*readPins);
 
 // ==================== LEDs ===================
-LED_PinNumber LED1(16);
+LED_uC LED1(16);
 
 //sometimes OS takes 6 seconds to recongnize keyboard, LED blinks from the begining
 void wait()
@@ -111,26 +111,26 @@ Row_uC row_L1(1, readPins, READ_PIN_COUNT, ptrsKeys_L1);
 /*
 //prints 0 1
 Key* ptrsKeys_R0[] = { &s_0, &s_z, &s_z, &s_z, &s_1, &s_z, &s_z, &s_z };
-const uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
+uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
 Row_ShiftRegisters row_R0(8, READ_PIN_COUNT_R0, ptrsKeys_R0);
 
 //prints a b
 Key* ptrsKeys_R1[] = { &s_a, &s_z, &s_z, &s_z, &s_b, &s_z, &s_z, &s_z };
-const uint8_t READ_PIN_COUNT_R1 = sizeof(ptrsKeys_R1)/sizeof(*ptrsKeys_R1);
+uint8_t READ_PIN_COUNT_R1 = sizeof(ptrsKeys_R1)/sizeof(*ptrsKeys_R1);
 Row_ShiftRegisters row_R1(9, READ_PIN_COUNT_R1, ptrsKeys_R1);
 */
 /*
 //prints 0 1 2
 Key* ptrsKeys_R0[] = { &s_0, &s_z, &s_z, &s_z, &s_1, &s_z, &s_z, &s_z,
                        &s_2, &s_z, &s_z, &s_z };
-const uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
+uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
 Row_ShiftRegisters row_R0(8, READ_PIN_COUNT_R0, ptrsKeys_R0);
 */
 /*
 //prints 0 1 2 3
 Key* ptrsKeys_R0[] = { &s_0, &s_z, &s_z, &s_z, &s_1, &s_z, &s_z, &s_z,
                        &s_2, &s_z, &s_z, &s_z, &s_3, &s_z, &s_z, &s_z };
-const uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
+uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
 Row_ShiftRegisters row_R0(8, READ_PIN_COUNT_R0, ptrsKeys_R0);
 */
 /*
@@ -138,7 +138,7 @@ Row_ShiftRegisters row_R0(8, READ_PIN_COUNT_R0, ptrsKeys_R0);
 Key* ptrsKeys_R0[] = { &s_0, &s_z, &s_z, &s_z, &s_1, &s_z, &s_z, &s_z,
                        &s_2, &s_z, &s_z, &s_z, &s_3, &s_z, &s_z, &s_z,
                        &s_4, &s_z, &s_z, &s_z, &s_5, &s_z, &s_z, &s_z };
-const uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
+uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
 Row_ShiftRegisters row_R0(8, READ_PIN_COUNT_R0, ptrsKeys_R0);
 */
 
@@ -147,7 +147,7 @@ Key* ptrsKeys_R0[] = { &s_0, &s_z, &s_z, &s_z, &s_1, &s_z, &s_z, &s_z,
                        &s_2, &s_z, &s_z, &s_z, &s_3, &s_z, &s_z, &s_z,
                        &s_4, &s_z, &s_z, &s_z, &s_5, &s_z, &s_z, &s_z,
                        &s_6, &s_z, &s_z, &s_z, &s_3, &s_4, &s_5, &s_6 };
-const uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
+uint8_t READ_PIN_COUNT_R0 = sizeof(ptrsKeys_R0)/sizeof(*ptrsKeys_R0);
 Row_ShiftRegisters row_R0(0, READ_PIN_COUNT_R0, ptrsKeys_R0);
 
 //prints a b c d u v w x
@@ -155,19 +155,18 @@ Key* ptrsKeys_R1[] = { &s_a, &s_z, &s_z, &s_z, &s_b, &s_z, &s_z, &s_z,
                        &s_c, &s_z, &s_z, &s_z, &s_d, &s_z, &s_z, &s_z,
                        &s_e, &s_z, &s_z, &s_z, &s_f, &s_z, &s_z, &s_z,
                        &s_g, &s_z, &s_z, &s_z, &s_u, &s_v, &s_w, &s_x };
-const uint8_t READ_PIN_COUNT_R1 = sizeof(ptrsKeys_R1)/sizeof(*ptrsKeys_R1);
+uint8_t READ_PIN_COUNT_R1 = sizeof(ptrsKeys_R1)/sizeof(*ptrsKeys_R1);
 Row_ShiftRegisters row_R1(1, READ_PIN_COUNT_R1, ptrsKeys_R1);
 
 // ################### MAIN ####################
 void setup()
 {
     Keyboard.begin();
-
-    wait();
     SPI.begin();
     row_R0.begin();
     row_R1.begin();
 
+    wait();
     Keyboard.println(F("keybrd_shift_reg.ino"));
 }
 
diff --git a/src/Debouncer_Samples.h b/src/Debouncer_Samples.h
index 3739a30..01edffd 100644
--- a/src/Debouncer_Samples.h
+++ b/src/Debouncer_Samples.h
@@ -1,5 +1,6 @@
-#ifndef DEBOUNCER_4SAMPLES_H
-#define DEBOUNCER_4SAMPLES_H
+#ifndef DEBOUNCER_SAMPLES_H
+#define DEBOUNCER_SAMPLES_H
+
 #include <Arduino.h>
 #include <inttypes.h>
 #include <config_keybrd.h>
diff --git a/src/Row.cpp b/src/Row.cpp
index 7c9a82e..1dec597 100644
--- a/src/Row.cpp
+++ b/src/Row.cpp
@@ -1,13 +1,13 @@
 #include "Row.h"
 /*
-send() calls key's press() or release() function if it was pressed or released.
+send() calls key's press() or release() function if key was pressed or released.
 Both parameters are bitwise.
 */
 void Row::send(const uint8_t readPinCount, const read_pins_t debouncedChanged)
 {
     read_pins_t isFallingEdge;                  //bitwise, 1 means falling edge
     read_pins_t isRisingEdge;                   //bitwise, 1 means rising edge
-    read_pins_t readMask;                       //bitwise, active read bit is 1
+    read_pins_t readMask;                       //bitwise, active bit is 1
     uint8_t i;                                  //index for ptrsKeys[i] array
 
     //bit=1 if last debounced changed from 1 to 0, else bit=0
@@ -34,5 +34,5 @@ void Row::send(const uint8_t readPinCount, const read_pins_t debouncedChanged)
             
 void Row::keyWasPressed()
 {
-    //empty in Row class.  To unstick sticky keys, override keyWasPressed() in derived class.
+    //empty in Row class.  To unstick sticky keys, override keyWasPressed() in derived Row class.
 }
diff --git a/src/Row.h b/src/Row.h
index f8f5b64..5292b2b 100644
--- a/src/Row.h
+++ b/src/Row.h
@@ -1,5 +1,6 @@
 #ifndef ROW_H
 #define ROW_H
+
 #include <Arduino.h>
 #include <inttypes.h>
 #include <config_keybrd.h>
@@ -13,7 +14,8 @@ class Row
         Key *const *const ptrsKeys;             //array of Key pointers
         virtual void keyWasPressed();
     protected:
-        read_pins_t debounced;                  //bitwise, 1 means pressed, 0 means released
+        read_pins_t debounced;                  //bitwise state of keys after debouncing
+                                                // 1 means pressed, 0 means released
         void send(const uint8_t readPinCount, const read_pins_t debouncedChanged);
     public:
         Row(Key *const ptrsKeys[]) : ptrsKeys(ptrsKeys), debounced(0) { }
diff --git a/src/Row_ShiftRegisters.cpp b/src/Row_ShiftRegisters.cpp
index 69d101b..6f599bb 100644
--- a/src/Row_ShiftRegisters.cpp
+++ b/src/Row_ShiftRegisters.cpp
@@ -1,17 +1,21 @@
 #include "Row_ShiftRegisters.h"
 
+/* Call begin() once in sketch setup()
+*/
+void Row_ShiftRegisters::begin()
+{
+    scanner.begin();
+}
+
+/* process() scans the row and calls any newly pressed or released keys.
+Bitwise variables are 1 bit per key.
+*/
 void Row_ShiftRegisters::process()
 {
-    //these variables are all bitwise, one bit per key
-    read_pins_t readState;                       //1 means pressed, 0 means released
-    read_pins_t debouncedChanged;               //1 means debounced changed
+    read_pins_t readState;                      //bitwise, 1 means key is pressed, 0 means released
+    read_pins_t debouncedChanged;               //bitwise, 1 means debounced changed
 
     readState = scanner.scan();
     debouncedChanged = debouncer.debounce(readState, debounced);
     send(READ_PIN_COUNT, debouncedChanged);
 }
-
-void Row_ShiftRegisters::begin()
-{
-    scanner.begin();
-}
diff --git a/src/Row_ShiftRegisters.h b/src/Row_ShiftRegisters.h
index f8aee4b..6cb126a 100644
--- a/src/Row_ShiftRegisters.h
+++ b/src/Row_ShiftRegisters.h
@@ -4,35 +4,42 @@
 #include <Row.h>
 #include <Scanner_ShiftRegs74HC165.h>
 #include <Debouncer_Samples.h>
-//#include <Debouncer_Not.h>
 
-/* Row_DH_IOE is a row connected to an Input/Output Expander.
+/* Row_ShiftRegisters is a row connected to shift registers.
 
 Instantiation
 -------------
 Definition of DELAY_MICROSECONDS is explained in Row.cpp.
-Example instantiation of a row:
+Example instantiation of a Row_ShiftRegisters:
 
-    const unsigned int Row::DELAY_MICROSECONDS = 1000;
-
-    todo
+    const uint8_t Scanner_ShiftRegs74HC165::SHIFT_LOAD = 10;
+    const bool Scanner_ShiftRegs74HC165::STROBE_ON = LOW;    //logic level of strobe on, active low
+    const bool Scanner_ShiftRegs74HC165::STROBE_OFF = HIGH;  //logic level of strobe off
 
     Key* const ptrsKeys_0[] = { &k_00, &k_01, &k_02, &k_03, &k_04, &k_05 };
-    Row_ShiftRegisters row_0(uint8_t BYTE_COUNT, ptrsKeys_0);
+    uint8_t READ_PIN_COUNT_0 = sizeof(ptrsKeys_0)/sizeof(*ptrsKeys_0);
+    Row_ShiftRegisters row_0(1, READ_PIN_COUNT_0, ptrsKeys_0);
 
-Number of pins in colPort0 should equal number of keys in ptrsKeys_0[] array.
-    if a pin is missing, a key will be unresposive
-    if a Key pointer is missing, the keyboard will fail in an unprdictable way
+call begin() from sketch setup():
+    void setup()
+    {
+        Keyboard.begin();
+        SPI.begin();
+        row_0.begin();
+    }
+
+READ_PIN_COUNT should equal number of keys in ptrsKeys_0[] array.
+    if READ_PIN_COUNT is too small, a key will be unresposive
+    if READ_PIN_COUNT is too large, the keyboard will fail in an unpredictable way
 */
 class Row_ShiftRegisters : public Row
 {
     private:
         Scanner_ShiftRegs74HC165 scanner;
         Debouncer_Samples debouncer;
-        //Debouncer_Not debouncer; //passed test
         const uint8_t READ_PIN_COUNT;           //number of read pins
     public:
-        Row_ShiftRegisters(const uint8_t STROBE_PIN, uint8_t READ_PIN_COUNT, Key *const ptrsKeys[])
+        Row_ShiftRegisters(const uint8_t STROBE_PIN, const uint8_t READ_PIN_COUNT, Key *const ptrsKeys[])
             : Row(ptrsKeys), scanner(STROBE_PIN, READ_PIN_COUNT), READ_PIN_COUNT(READ_PIN_COUNT) { }
         void begin();
         void process();
diff --git a/src/Row_uC.cpp b/src/Row_uC.cpp
index 889c564..81efc3d 100644
--- a/src/Row_uC.cpp
+++ b/src/Row_uC.cpp
@@ -1,13 +1,12 @@
 #include "Row_uC.h"
 
-/*
-process() scans the row and calls any newly pressed or released keys.
+/* process() scans the row and calls any newly pressed or released keys.
+Bitwise variables are 1 bit per key.
 */
 void Row_uC::process()
 {
-    //these variables are all bitwise, one bit per key
-    read_pins_t readState;                       //1 means pressed, 0 means released
-    read_pins_t debouncedChanged;               //1 means debounced changed
+    read_pins_t readState;                      //bitwise, 1 means key is pressed, 0 means released
+    read_pins_t debouncedChanged;               //bitwise, 1 means debounced changed
 
     readState = scanner.scan();
     debouncedChanged = debouncer.debounce(readState, debounced);
diff --git a/src/Row_uC.h b/src/Row_uC.h
index 2ed2fe2..2c81a35 100644
--- a/src/Row_uC.h
+++ b/src/Row_uC.h
@@ -10,10 +10,9 @@
 Instantiation
 -------------
 Definition of DELAY_MICROSECONDS is explained in Row.cpp.
-Example instantiation of a row:
+Example instantiation of a Row_uC:
 
-    const unsigned int Row::DELAY_MICROSECONDS = 1000;
-    const bool Scanner_uC::STROBE_ON = LOW;   //logic level of strobe on
+    const bool Scanner_uC::STROBE_ON = LOW;   //logic level of strobe on, active low
     const bool Scanner_uC::STROBE_OFF = HIGH; //logic level of strobe off
 
     const uint8_t readPins[] = {0,1,2,3,7,8};
@@ -24,14 +23,14 @@ Example instantiation of a row:
 
 Number of readPins should equal number of keys in ptrsKeys_0[] array.
     if a readPins is missing, a key will be unresposive
-    if a Key pointer is missing, the keyboard will fail in an unprdictable way
+    if a Key pointer is missing, the keyboard will fail in an unpredictable way
 */
 class Row_uC : public Row
 {
     private:
         Scanner_uC scanner;
         Debouncer_Samples debouncer;
-        const uint8_t READ_PIN_COUNT;           //number of read pins
+        const uint8_t READ_PIN_COUNT;
     public:
         Row_uC(const uint8_t strobePin, const uint8_t READ_PINS[], const uint8_t READ_PIN_COUNT,
                 Key *const ptrsKeys[])
diff --git a/src/Scanner_Port.cpp b/src/Scanner_Port.cpp
index e3b99ab..72d5411 100644
--- a/src/Scanner_Port.cpp
+++ b/src/Scanner_Port.cpp
@@ -1,21 +1,21 @@
 #include "Scanner_Port.h"
-/*
-Strobes the row and reads the columns.
+
+/* scan() strobes the row's STROBE_PIN and retuns state of port's input pins.
+Bitwise variables are 1 bit per key.
 */
 uint8_t Scanner_Port::scan()
 {
-    uint8_t readState;
+    uint8_t readState;                          //bitwise, 1 means key is pressed, 0 means released
 
-    //strobe row on
+    //strobe on
     refPortWrite.write(STROBE_PIN, STROBE_ON);
     delayMicroseconds(3);                       //time to stablize voltage
 
     //read the port pins
     readState = refPortRead.read();
 
-    //strobe row off
+    //strobe off
     refPortWrite.write(STROBE_PIN, STROBE_OFF);
    
-    //return refPortRead.getPortState();
     return readState;
 }
diff --git a/src/Scanner_Port.h b/src/Scanner_Port.h
index 36d1d44..15effe6 100644
--- a/src/Scanner_Port.h
+++ b/src/Scanner_Port.h
@@ -1,21 +1,23 @@
 #ifndef SCANNER_PORT_H
 #define SCANNER_PORT_H
+
 #include <Arduino.h>
 #include <inttypes.h>
 #include <PortWrite.h>
 #include <PortRead.h>
 
 /* Scanner_Port uses bit manipulation to read all pins of one port.
+The ports are normally from an I/O Expander, but could also be ports from an AVR uC.
 The maximum keys per row is 8, because ports have a maximum of 8 pins each.
 */
 class Scanner_Port
 {
     private:
         static const bool STROBE_ON;        //HIGH or LOW logic level of strobe on, active state
-        static const bool STROBE_OFF;           //logic level of strobe off, complement of STROBE_ON
-        PortWrite& refPortWrite;                //this row's IC port
-        const uint8_t STROBE_PIN;            //bitwise, 1 indicates IC pin connected to this row
-        PortRead& refPortRead;
+        static const bool STROBE_OFF;       //logic level of strobe off, complement of STROBE_ON
+        PortWrite& refPortWrite;            //the IC port containing the STROBE_PIN
+        const uint8_t STROBE_PIN;           //bitwise, 1 indicates IC pin connected to this row
+        PortRead& refPortRead;              //the IC's read port
     public:
         Scanner_Port(PortWrite &refPortWrite, const uint8_t STROBE_PIN, PortRead& refPortRead)
             : refPortWrite(refPortWrite), STROBE_PIN(STROBE_PIN), refPortRead(refPortRead) {}
diff --git a/src/Scanner_ShiftRegs74HC165.cpp b/src/Scanner_ShiftRegs74HC165.cpp
index 702a5f6..bf251ea 100644
--- a/src/Scanner_ShiftRegs74HC165.cpp
+++ b/src/Scanner_ShiftRegs74HC165.cpp
@@ -15,12 +15,12 @@ void Scanner_ShiftRegs74HC165::begin()
     digitalWrite(SHIFT_LOAD, HIGH);
 }
 
-/*
-returns readState.
+/* scan() strobes the row's STROBE_PIN and retuns state of the shift register's input pins.
+Bitwise variables are 1 bit per key.
 */
 read_pins_t Scanner_ShiftRegs74HC165::scan()
 {
-    read_pins_t readState = 0;
+    read_pins_t readState = 0;                  //bitwise, 1 means key is pressed, 0 means released
 
     //strobe row on
     digitalWrite(STROBE_PIN, STROBE_ON);
@@ -35,7 +35,7 @@ read_pins_t Scanner_ShiftRegs74HC165::scan()
     digitalWrite(STROBE_PIN, STROBE_OFF);
 
     //for testing on breadboard, clear unpowered pins
-    readState &= 0b11110001000100010001000100010001; //todo
+    readState &= 0b11110001000100010001000100010001; //todo delete this line
 
     return readState;
 }
diff --git a/src/Scanner_ShiftRegs74HC165.h b/src/Scanner_ShiftRegs74HC165.h
index 594fdf7..d2c57a7 100644
--- a/src/Scanner_ShiftRegs74HC165.h
+++ b/src/Scanner_ShiftRegs74HC165.h
@@ -1,5 +1,6 @@
 #ifndef ROWSCANNER_SHIFTREGS74HC165_H
 #define ROWSCANNER_SHIFTREGS74HC165_H
+
 #include <Arduino.h>
 #include <inttypes.h>
 #include <config_keybrd.h>
@@ -8,12 +9,8 @@
 #include <PortRead.h>
 
 /* Scanner_ShiftRegs74HC165 reads shift registers.
-shift registers 74HC165 is Parallel-In-Serial-Out (PISO)
-Upto 4 shift registers can be in a daisy chained.
-
-In sketch:
-    const uint8_t Scanner_ShiftRegs74HC165::SHIFT_LOAD = 10;
-    call begin() from setup()
+shift registers 74HC165 are Parallel-In-Serial-Out (PISO)
+Upto 4 shift registers can be in a daisy chained for a total of 32 read pins.
 
 For active low:
     const bool Scanner_ShiftRegs74HC165::STROBE_ON = LOW;
@@ -27,7 +24,7 @@ For active high:
     //shift register parallel input pins have 10k pull-down resistors grounded
     //controller's MISO pin is connected to shift register's serial output (QH) pin
 
-In addition, each row needs to be connected to a strobe pin from controller.
+In addition, each row needs to be connected to a strobe pin from the controller.
 
  todo move this to tutorial
 The shift register needs 5 wires.
@@ -45,7 +42,7 @@ class Scanner_ShiftRegs74HC165
         const uint8_t STROBE_PIN;               //Arduino pin number connected to this row
         const uint8_t BYTE_COUNT;               //number of bytes to read from shift registers
     public:
-        Scanner_ShiftRegs74HC165(const uint8_t STROBE_PIN, uint8_t READ_PIN_COUNT);
+        Scanner_ShiftRegs74HC165(const uint8_t STROBE_PIN, const uint8_t READ_PIN_COUNT);
         virtual read_pins_t scan();
         void begin();
 };
diff --git a/src/Scanner_uC.cpp b/src/Scanner_uC.cpp
index bbced6a..e9a2a19 100644
--- a/src/Scanner_uC.cpp
+++ b/src/Scanner_uC.cpp
@@ -1,5 +1,13 @@
 #include "Scanner_uC.h"
 
+/* Scanner_uC functions call Arduino's Digital Pins functions
+https://www.arduino.cc/en/Tutorial/DigitalPins
+https://www.arduino.cc/en/Reference/PinMode
+https://www.arduino.cc/en/Reference/DigitalWrite
+https://www.arduino.cc/en/Reference/DigitalRead
+https://www.arduino.cc/en/Reference/Constants > Digital Pins modes: INPUT, INPUT_PULLUP, and OUTPUT
+*/
+
 /* constructor
 */
 Scanner_uC::Scanner_uC(const uint8_t STROBE_PIN,
@@ -13,9 +21,9 @@ Scanner_uC::Scanner_uC(const uint8_t STROBE_PIN,
 
     if (STROBE_ON == LOW)               //if active low
     {
-        mode = INPUT_PULLUP;            //uses internal pull-up resistor
+        mode = INPUT_PULLUP;            //use internal pull-up resistor
     }
-    else
+    else                                //if active high
     {
         mode = INPUT;                   //requires external pull-down resistor
     }
@@ -27,19 +35,13 @@ Scanner_uC::Scanner_uC(const uint8_t STROBE_PIN,
     }
 }
 
-/* scan() Strobes the row and reads the columns.
-Sets READ_PIN_COUNT and returns readState.
-
-https://www.arduino.cc/en/Tutorial/DigitalPins
-https://www.arduino.cc/en/Reference/PinMode
-https://www.arduino.cc/en/Reference/DigitalWrite
-https://www.arduino.cc/en/Reference/DigitalRead
-https://www.arduino.cc/en/Reference/Constants > Digital Pins modes: INPUT, INPUT_PULLUP, and OUTPUT
+/* scan() strobes the row's STROBE_PIN and retuns state of READ_PINS.
+Bitwise variables are 1 bit per key.
 */
 read_pins_t Scanner_uC::scan()
 {
-    read_pins_t readState = 0;                   //bitwise, one col per bit, 1 means key is pressed
-    read_pins_t readMask = 1;                   //bitwise, one col per bit, active col bit is 1
+    read_pins_t readState = 0;                  //bitwise, 1 means key is pressed, 0 means released
+    read_pins_t readMask = 1;                   //bitwise, active bit is 1
 
     //strobe row on
     digitalWrite(STROBE_PIN, STROBE_ON);
@@ -58,6 +60,5 @@ read_pins_t Scanner_uC::scan()
     //strobe row off
     digitalWrite(STROBE_PIN, STROBE_OFF);
 
-   // readPinCount = READ_PIN_COUNT;
     return readState;
 }
diff --git a/src/Scanner_uC.h b/src/Scanner_uC.h
index 72e8225..e2658eb 100644
--- a/src/Scanner_uC.h
+++ b/src/Scanner_uC.h
@@ -1,5 +1,6 @@
 #ifndef SCANNER_UC_H
 #define SCANNER_UC_H
+
 #include <Arduino.h>
 #include <inttypes.h>
 #include <config_keybrd.h>
diff --git a/src/config_keybrd.h b/src/config_keybrd.h
index 9aef07d..5abec2b 100644
--- a/src/config_keybrd.h
+++ b/src/config_keybrd.h
@@ -4,23 +4,23 @@
 
 /* size of read_pins_t depends on the maximum number of pins scanned by RowScanner.
 By default, read_pins_t is set to the largest type.
-If your 8-bit AVR is running low on memory, using a smaller type saves SRAM.
+If your 8-bit AVR (Teensy 2) is running low on memory, using a smaller type saves SRAM.
 Using smaller types on a 32-bit uC (Teensy LC) would accomplish nothing.
 */
 
-/* Uncomment a typedef read_pins_t size that covers all col pins of all RowScanner objects i.e.
+/* Use a read_pins_t size that covers all read pins of all RowScanner objects i.e.
     For Scanner_uC, Scanner_uC::READ_PIN_COUNT
     For Scanner_ShiftRegs74HC165, Scanner_ShiftRegs74HC165::READ_PIN_COUNT
     For Scanner_Port, cover the last 1 bit in Scanner_Port::strobePin
 */
-typedef uint8_t read_pins_t;
+//typedef uint8_t read_pins_t;
 //typedef uint16_t read_pins_t;
-//typedef uint32_t read_pins_t;
+typedef uint32_t read_pins_t;
 
-/* SAMPLE_COUNT = 4 is very reliable for a keyboard.
+/* SAMPLE_COUNT is used in Debouncer_Samples.h
+SAMPLE_COUNT = 4 is very reliable for a keyboard.
 Split keyboards with a long connecting wire or in environment with
 strong electromagnetic interference (EMI) may need a larger SAMPLE_COUNT for reliability.
-SAMPLE_COUNT is used in Debouncer_Samples.h
 */
 #define SAMPLE_COUNT 4      //number of consecutive equal bits needed to change a debounced bit