diff --git a/src/DebouncerInterface.h b/src/DebouncerInterface.h
index dab6ecd..1c6d56b 100644
--- a/src/DebouncerInterface.h
+++ b/src/DebouncerInterface.h
@@ -3,7 +3,7 @@
 
 #include <config_keybrd.h>
 
-/* DebouncerInterface is an interface class.
+/* 
 debounce() takes rawSignal and returns debounced signal.  Signals are bitwise.
 */
 class DebouncerInterface
diff --git a/src/Row.cpp b/src/Row.cpp
index f370365..cdf8fdf 100644
--- a/src/Row.cpp
+++ b/src/Row.cpp
@@ -1,4 +1,28 @@
 #include "Row.h"
+
+/* constructor
+*/
+Row::Row(ScannerInterface& refScanner, const uint8_t strobePin,
+        Key* const ptrsKeys[], const uint8_t readPinCount)
+    : refScanner(refScanner), strobePin(strobePin),
+    ptrsKeys(ptrsKeys), readPinCount(readPinCount), debounced(0)
+{
+    refScanner.begin(strobePin);
+}
+
+/* process() scans the row and calls any newly pressed or released keys.
+Bitwise variables are 1 bit per key.
+*/
+void Row::process()
+{
+    read_pins_t readState;                      //bitwise, 1 means key is pressed, 0 means released
+    read_pins_t debouncedChanged;               //bitwise, 1 means debounced changed
+
+    readState = refScanner.scan(strobePin);
+    debouncedChanged = debouncer.debounce(readState, debounced);
+    send(readPinCount, debouncedChanged);
+}
+
 /*
 send() calls key's press() or release() function if key was pressed or released.
 Both parameters are bitwise.
diff --git a/src/Row.h b/src/Row.h
index a0b797a..a042aea 100644
--- a/src/Row.h
+++ b/src/Row.h
@@ -5,19 +5,29 @@
 #include <inttypes.h>
 #include <config_keybrd.h>
 #include <Key.h>
+#include <ScannerInterface.h>
+#include <Debouncer_Samples.h>
 
-/* Row is an abstract base class.
+/*
+strobePin has one of two formats:
+ * if refScanner a Scanner_uC, then strobePin is an Arduino pin number connected to this row
+ * if refScanner a Scanner_IOE, then strobePin is bitwise, 1 indicating IC pin connected to this row
 */
 class Row
 {
     private:
+        ScannerInterface& refScanner;
+        const uint8_t strobePin;                //pin connected to this row (details above)
         Key *const *const ptrsKeys;             //array of Key pointers
+        const uint8_t readPinCount;             //number of read pins
+        Debouncer_Samples debouncer;
         virtual void keyWasPressed();
-    protected:
+    protected://todo is protected needed?
         read_pins_t debounced;      //bitwise state of keys after debouncing, 1=pressed, 0=released
         void send(const uint8_t readPinCount, const read_pins_t debouncedChanged);
     public:
-        Row(Key* const ptrsKeys[]) : ptrsKeys(ptrsKeys), debounced(0) { }
-        virtual void process()=0;
+        Row(ScannerInterface& refScanner, const uint8_t strobePin,
+                Key* const ptrsKeys[], const uint8_t readPinCount);
+        void process();
 };
 #endif
diff --git a/src/Row_IOE.cpp b/src/Row_IOE.cpp
deleted file mode 100644
index 066623a..0000000
--- a/src/Row_IOE.cpp
+++ /dev/null
@@ -1,12 +0,0 @@
-#include "Row_IOE.h"
-
-void Row_IOE::process()
-{
-    //these variables are all bitwise, one bit per key
-    uint8_t readState;                          //1 means pressed, 0 means released
-    uint8_t debouncedChanged;                   //1 means debounced changed
-
-    readState = scanner.scan();
-    debouncedChanged = debouncer.debounce(readState, debounced);
-    send(readPinCount, debouncedChanged);
-}
diff --git a/src/Row_IOE.h b/src/Row_IOE.h
deleted file mode 100644
index 2461c84..0000000
--- a/src/Row_IOE.h
+++ /dev/null
@@ -1,26 +0,0 @@
-#ifndef ROW_IOE_H
-#define ROW_IOE_H
-
-#include <Row.h>
-#include <Scanner_Port.h>
-#include <Debouncer_Samples.h>
-class PortWriteInterface;
-class PortReadInterface;
-
-/* Row_IOE is a row connected to an I/O Expander.
-Configuration and Instantiation instructions are in keybrd/src/Row_uC.h
-*/
-class Row_IOE : public Row
-{
-    private:
-        Scanner_Port scanner;
-        Debouncer_Samples debouncer;
-        const uint8_t readPinCount;
-    public:
-        Row_IOE(PortWriteInterface& refPortWrite, const uint8_t strobePin,
-                  PortReadInterface& refPortRead, const uint8_t readPinCount, Key *const ptrsKeys[])
-            : Row(ptrsKeys), scanner(refPortWrite, strobePin, refPortRead),
-              readPinCount(readPinCount) { }
-        void process();
-};
-#endif
diff --git a/src/Row_ShiftRegisters.cpp b/src/Row_ShiftRegisters.cpp
deleted file mode 100644
index cdeee48..0000000
--- a/src/Row_ShiftRegisters.cpp
+++ /dev/null
@@ -1,21 +0,0 @@
-#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()
-{
-    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(readPinCount, debouncedChanged);
-}
diff --git a/src/Row_ShiftRegisters.h b/src/Row_ShiftRegisters.h
deleted file mode 100644
index a3f5aac..0000000
--- a/src/Row_ShiftRegisters.h
+++ /dev/null
@@ -1,48 +0,0 @@
-#ifndef ROW_SHIFTREGISTERS_H
-#define ROW_SHIFTREGISTERS_H
-
-#include <Row.h>
-#include <Scanner_ShiftRegs74HC165.h>
-#include <Debouncer_Samples.h>
-
-/* Row_ShiftRegisters is a row connected to shift registers.
-
-Instantiation
--------------
-Scanner_ShiftRegs74HC165.h has instructions for hardware and setting active state.
-Example instantiation of a Row_ShiftRegisters:
-
-    const uint8_t Scanner_ShiftRegs74HC165::SHIFT_LOAD = 10;
-    const bool Scanner_ShiftRegs74HC165::STROBE_ON = LOW;    //active low
-    const bool Scanner_ShiftRegs74HC165::STROBE_OFF = HIGH;
-
-    Key* const ptrsKeys_0[] = { &k_00, &k_01, &k_02, &k_03, &k_04, &k_05 };
-    uint8_t readPinCount_0 = sizeof(ptrsKeys_0)/sizeof(*ptrsKeys_0);
-    Row_ShiftRegisters row_0(1, readPinCount_0, ptrsKeys_0);
-
-call begin() from sketch setup():
-    void setup()
-    {
-        Keyboard.begin();
-        SPI.begin();
-        row_0.begin();
-    }
-
-readPinCount should equal number of keys in ptrsKeys_0[] array.
-    if readPinCount is too small, a key will be unresponsive
-    if readPinCount is too large, the keyboard will fail in an unpredictable way
-*/
-class Row_ShiftRegisters : public Row
-{
-    private:
-        Scanner_ShiftRegs74HC165 scanner;
-        Debouncer_Samples debouncer;
-        const uint8_t readPinCount;           //number of read pins
-    public:
-        Row_ShiftRegisters(const uint8_t strobePin, const uint8_t readPinCount,
-                           Key* const ptrsKeys[])
-            : Row(ptrsKeys), scanner(strobePin, readPinCount), readPinCount(readPinCount) { }
-        void begin();
-        void process();
-};
-#endif
diff --git a/src/Row_uC.cpp b/src/Row_uC.cpp
deleted file mode 100644
index aba7ae5..0000000
--- a/src/Row_uC.cpp
+++ /dev/null
@@ -1,14 +0,0 @@
-#include "Row_uC.h"
-
-/* process() scans the row and calls any newly pressed or released keys.
-Bitwise variables are 1 bit per key.
-*/
-void Row_uC::process()
-{
-    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(readPinCount, debouncedChanged);
-}
diff --git a/src/Row_uC.h b/src/Row_uC.h
deleted file mode 100644
index d94fe0c..0000000
--- a/src/Row_uC.h
+++ /dev/null
@@ -1,41 +0,0 @@
-#ifndef ROW_UC_H
-#define ROW_UC_H
-
-#include <Row.h>
-#include <Scanner_uC.h>
-#include <Debouncer_Samples.h>
-
-/* Row_uC is a row connected to a microcontroller.
-
-Instantiation
--------------
-keybrd_library_developer_guide.md has instructions for ## Active state and diode orientation
-Example instantiation of a Row_uC:
-
-    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};
-    const uint8_t readPinCount = sizeof(readPins)/sizeof(*readPins);
-
-    Key* const ptrsKeys_0[] = { &k_00, &k_01, &k_02, &k_03, &k_04, &k_05 };
-    Row_uC row_0(21, readPins, readPinCount, ptrsKeys_0);
-
-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 unpredictable way
-*/
-class Row_uC : public Row
-{
-    private:
-        Scanner_uC scanner;
-        Debouncer_Samples debouncer;
-        const uint8_t readPinCount;
-    public:
-        Row_uC(const uint8_t strobePin, const uint8_t readPins[], const uint8_t readPinCount,
-               Key* const ptrsKeys[])
-            : Row(ptrsKeys), scanner(strobePin, readPins, readPinCount),
-              readPinCount(readPinCount) { }
-        void process();
-};
-#endif
diff --git a/src/ScannerInterface.h b/src/ScannerInterface.h
new file mode 100644
index 0000000..6b27994
--- /dev/null
+++ b/src/ScannerInterface.h
@@ -0,0 +1,14 @@
+#ifndef SCANNERINTERFACE_H
+#define SCANNERINTERFACE_H
+
+#include <config_keybrd.h>
+
+/* scan() retuns state of readPins.
+*/
+class ScannerInterface
+{
+    public:
+        virtual void begin(const uint8_t strobePin)=0;
+        virtual read_pins_t scan(const uint8_t strobePin)=0;
+};
+#endif
diff --git a/src/Scanner_Port.cpp b/src/Scanner_Port.cpp
index a855bb4..f168d30 100644
--- a/src/Scanner_Port.cpp
+++ b/src/Scanner_Port.cpp
@@ -3,7 +3,7 @@
 /* scan() strobes the row's strobePin and retuns state of port's input pins.
 Bitwise variables are 1 bit per key.
 */
-uint8_t Scanner_Port::scan()
+uint8_t Scanner_Port::scan(const uint8_t strobePin)
 {
     uint8_t readState;                          //bitwise, 1 means key is pressed, 0 means released
 
diff --git a/src/Scanner_Port.h b/src/Scanner_Port.h
index a6c92da..2ff8c5f 100644
--- a/src/Scanner_Port.h
+++ b/src/Scanner_Port.h
@@ -18,13 +18,10 @@ class Scanner_Port
         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
         PortWriteInterface& refPortWrite;            //the IC port containing the strobePin
-        const uint8_t strobePin;            //bitwise, 1 indicates IC pin connected to this row
         PortReadInterface& refPortRead;              //the IC's read port
     public:
-        Scanner_Port(PortWriteInterface &refPortWrite, const uint8_t strobePin,
-              PortReadInterface& refPortRead)
-            : refPortWrite(refPortWrite), strobePin(strobePin),
-              refPortRead(refPortRead) {}
-        uint8_t scan();
+        Scanner_Port(PortWriteInterface &refPortWrite, PortReadInterface& refPortRead)
+            : refPortWrite(refPortWrite), refPortRead(refPortRead) {}
+        uint8_t scan(const uint8_t strobePin);
 };
 #endif
diff --git a/src/Scanner_uC.cpp b/src/Scanner_uC.cpp
index d86f3ac..09f93c0 100644
--- a/src/Scanner_uC.cpp
+++ b/src/Scanner_uC.cpp
@@ -10,47 +10,51 @@ https://www.arduino.cc/en/Reference/Constants > Digital Pins modes: INPUT, INPUT
 
 /* constructor
 */
-Scanner_uC::Scanner_uC(const uint8_t strobePin,
-                       const uint8_t readPins[], const uint8_t readPinCount)
-    : strobePin(strobePin), readPins(readPins), readPinCount(readPinCount)
+Scanner_uC::Scanner_uC(const bool strobeOn, const uint8_t readPins[], const uint8_t readPinCount)
+    : strobeOn(strobeOn), strobeOff(!strobeOn), readPins(readPins), readPinCount(readPinCount)
 {
     uint8_t mode;
 
-    //configure row
-    pinMode(strobePin, OUTPUT);
-
-    if (STROBE_ON == LOW)               //if active low
-    {
-        mode = INPUT_PULLUP;            //use internal pull-up resistor
-    }
-    else                                //if active high
-    {
-        mode = INPUT;                   //requires external pull-down resistor
-    }
-
     //configure read pins
+    if (strobeOn == LOW)                        //if active low
+    {
+        mode = INPUT_PULLUP;                    //use internal pull-up resistor
+    }
+    else                                        //if active high
+    {
+        mode = INPUT;                           //requires external pull-down resistor
+    }
+
     for (uint8_t i=0; i < readPinCount; i++)
     {
         pinMode(readPins[i], mode);
     }
 }
 
+/*
+Configure row-strobe pin to output.
+*/
+void Scanner_uC::begin(const uint8_t strobePin)
+{
+    pinMode(strobePin, OUTPUT);
+}
+
 /* scan() strobes the row's strobePin and retuns state of readPins.
 Bitwise variables are 1 bit per key.
 */
-read_pins_t Scanner_uC::scan()
+read_pins_t Scanner_uC::scan(const uint8_t strobePin)
 {
     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(strobePin, STROBE_ON);
+    digitalWrite(strobePin, strobeOn);
     delayMicroseconds(3);                       //time to stablize voltage
 
     //read all the read pins
     for (uint8_t i=0; i < readPinCount; i++)
     {
-        if ( digitalRead(readPins[i]) == STROBE_ON )
+        if ( digitalRead(readPins[i]) == strobeOn )
         {
             readState |= readMask;
         }
@@ -58,7 +62,7 @@ read_pins_t Scanner_uC::scan()
     }
 
     //strobe row off
-    digitalWrite(strobePin, STROBE_OFF);
+    digitalWrite(strobePin, strobeOff);
 
     return readState;
 }
diff --git a/src/Scanner_uC.h b/src/Scanner_uC.h
index bc69169..f344e1b 100644
--- a/src/Scanner_uC.h
+++ b/src/Scanner_uC.h
@@ -4,24 +4,23 @@
 #include <Arduino.h>
 #include <inttypes.h>
 #include <config_keybrd.h>
-#include <PortWriteInterface.h>
-#include <PortReadInterface.h>
+#include <ScannerInterface.h>
+//#include <PortWriteInterface.h>todo not needed?
+//#include <PortReadInterface.h>
 
 /* Scanner_uC class uses Arduino pin numbers (not port pin numbers).
-Constructor is in Scanner_uC.cpp
+Limit number of readPins to size of read_pins_t, which is defined in config_keybrd.h
 */
-class Scanner_uC
+class Scanner_uC : public ScannerInterface
 {
     private:
-        static const bool STROBE_ON;            //logic level of strobe on, HIGH or LOW
-        static const bool STROBE_OFF;           //logic level of strobe off, complement of STROBE_ON
-        const uint8_t strobePin;                //Arduino pin number connected to this row
+        const bool strobeOn;                    //logic level of strobe on, HIGH or LOW
+        const bool strobeOff;                   //logic level of strobe off, complement of strobeOn
         const uint8_t* const readPins;          //array of read pin numbers
-        const uint8_t readPinCount;             //number of read pins
+        const uint8_t readPinCount;             //number of readPins
     public:
-        Scanner_uC(const uint8_t strobePin,
-                   const uint8_t readPins[], const uint8_t readPinCount);
-        virtual read_pins_t scan();
+        Scanner_uC(const bool strobeOn, const uint8_t readPins[], const uint8_t readPinCount);
+        void begin(const uint8_t strobePin);
+        virtual read_pins_t scan(const uint8_t strobePin);
 };
 #endif
-
diff --git a/tutorials/keybrd_1_breadboard/keybrd_1_breadboard.ino b/tutorials/keybrd_1_breadboard/keybrd_1_breadboard.ino
index 398f3e9..980fdb1 100644
--- a/tutorials/keybrd_1_breadboard/keybrd_1_breadboard.ino
+++ b/tutorials/keybrd_1_breadboard/keybrd_1_breadboard.ino
@@ -2,38 +2,40 @@
 
 | Layout | **0** | **1** |
 |:------:|-------|-------|
-|  **0** | 1     | a     |
-|  **1** | b     | c     |
+|  **0** |   1   |   a   |
+|  **1** |   2   |   b   |
 */
 // ################## GLOBAL ###################
 // ================= INCLUDES ==================
+#include <Scanner_uC.h>
 #include <ScanDelay.h>
 #include <Code_Sc.h>
-#include <Row_uC.h>
+#include <Row.h>
 
 // ============ SPEED CONFIGURATION ============
 ScanDelay scanDelay(9000);
 
-// ================ ACTIVE STATE ===============
-const bool Scanner_uC::STROBE_ON = LOW;
-const bool Scanner_uC::STROBE_OFF = HIGH;
-
-// =================== PINS ====================
+// ================== SCANNER ==================
 uint8_t readPins[] = {14, 15};
-uint8_t READ_PIN_COUNT = sizeof(readPins)/sizeof(*readPins);
+uint8_t readPinCount = sizeof(readPins)/sizeof(*readPins);
+
+Scanner_uC scanner(LOW, readPins, readPinCount);
 
 // =================== CODES ===================
-Code_Sc s_1(KEY_1);
 Code_Sc s_a(KEY_A);
 Code_Sc s_b(KEY_B);
-Code_Sc s_c(KEY_C);
+
+Code_Sc s_1(KEY_1);
+Code_Sc s_2(KEY_2);
 
 // =================== ROWS ====================
 Key* ptrsKeys_0[] = { &s_1, &s_a };
-Row_uC row_0(0, readPins, READ_PIN_COUNT, ptrsKeys_0);
+uint8_t keyCount_0 = sizeof(ptrsKeys_0)/sizeof(*ptrsKeys_0);
+Row row_0(scanner, 0, ptrsKeys_0, keyCount_0);
 
-Key* ptrsKeys_1[] = { &s_b, &s_c };
-Row_uC row_1(1, readPins, READ_PIN_COUNT, ptrsKeys_1);
+Key* ptrsKeys_1[] = { &s_2, &s_b };
+uint8_t keyCount_1 = sizeof(ptrsKeys_1)/sizeof(*ptrsKeys_1);
+Row row_1(scanner, 1, ptrsKeys_1, keyCount_1);
 
 // ################### MAIN ####################
 void setup()
diff --git a/tutorials/tutorial_1_breadboard_keyboard.md b/tutorials/tutorial_1_breadboard_keyboard.md
index 75221f5..07ade64 100644
--- a/tutorials/tutorial_1_breadboard_keyboard.md
+++ b/tutorials/tutorial_1_breadboard_keyboard.md
@@ -99,7 +99,7 @@ Breadboard keyboard assembly instructions:
   * Teensy LC is on the left
   * switch leads are oriented to connect diodes to columns (pictured below)
   * diode cut offs connect terminal strips into columns
-  * diodes connect switches to blue buses; orient diodes with cathode (banded end) towards the row (bus strip)
+  * diodes connect switches to rows; orient diodes with cathode (banded end) towards the row (blue bus strip)
 
  ![switch orientation](keybrd_1_breadboard/switch_orientation.JPG "switch orientation")