diff --git a/src/PortRead_MCP23S17.cpp b/src/PortRead_MCP23S17.cpp
index 83fb56c..5a3d004 100644
--- a/src/PortRead_MCP23S17.cpp
+++ b/src/PortRead_MCP23S17.cpp
@@ -4,26 +4,36 @@
 PortRead_MCP23S17::begin() is not needed because port direction is already configured to input by default.
 SPI bus is configured in PortWrite_MCP23S17::begin().
 */
-void PortRead_MCP23S17::begin()
+void PortRead_MCP23S17::begin(const uint8_t strobeOn)
 {
+    uint8_t pullUp;                             //bitwise, 1 means internal pull-up resistor enabled
+
+    if (strobeOn == LOW)                        //if active low
+    {
+        pullUp = readPins;
+    }
+    else
+    {
+        pullUp = 0;
+    }
+
     pinMode(SS, OUTPUT);                        //configure controller's Slave Select pin to output
     digitalWrite(SS, HIGH);                     //disable Slave Select
     SPI.begin();
     SPI.beginTransaction(SPISettings (SPI_CLOCK_DIV8, MSBFIRST, SPI_MODE0)); //control SPI bus todo is slow clock needed?
-    digitalWrite(SS, LOW);                      //enable Slave Select
 
+    digitalWrite(SS, LOW);                      //enable Slave Select
       SPI.transfer(port.ADDR << 1);             //write command
       SPI.transfer(port.num);                   //configure IODIR
-      SPI.transfer(pullUp);                     //0=output (for LED), 1=input (for read)
-
+      SPI.transfer(readPins);                   //0=output (for LED), 1=input (for read)
     digitalWrite(SS, LOW);                      //enable Slave Select
-    digitalWrite(SS, HIGH);                     //disable Slave Select
 
+    digitalWrite(SS, HIGH);                     //disable Slave Select
       SPI.transfer(port.ADDR << 1);             //write command
       SPI.transfer(port.num + 0x0C);            //configure GPPU
       SPI.transfer(pullUp);                     //0=pull-up disabled (for LED), 1=pull-up enabled (for read)
-
     digitalWrite(SS, HIGH);                     //disable Slave Select
+
     //SPI.endTransaction() is not called to release the SPI bus
     // because keyboard only has one SPI device.
 }
diff --git a/src/PortRead_MCP23S17.h b/src/PortRead_MCP23S17.h
index 87e1ac1..f000884 100644
--- a/src/PortRead_MCP23S17.h
+++ b/src/PortRead_MCP23S17.h
@@ -5,12 +5,13 @@
 #include <SPI.h>
 #include <PortRead.h>
 #include "PortIOE.h"
+#include "Scanner_Port.h"
 
 /* One MCP23S17 I/O expander port connected to matrix columns.
 
 Instantiation todo
  ------------
-pullUp parameter is port's bitwise pin configuration
+readPins parameter is port's bitwise pin configuration
     1=configure as input (for pins connected to column)
     0=configure as output (for LED or not connected to a column)
 
@@ -21,17 +22,17 @@ Example instantiation for column port 1, with pins 2 and 3 connected to columns:
     PortIOE port1(1, 0);
     PortRead_MCP23S17 colPort1(port1, 2<<0 | 1<<3 );
 
-pullUp are read from pin 0 on up.
+readPins are read from pin 0 on up.
 
 */
 class PortRead_MCP23S17 : public PortRead
 {
     private:
         PortIOE& port;
-        const uint8_t pullUp;                   //bitwise, 1 means internal pull-up resistor enabled
+        const uint8_t readPins;                 //bitwise, 1 means internal pull-up resistor enabled
     public:
-        PortRead_MCP23S17(PortIOE& port, const uint8_t pullUp) : port(port), pullUp(pullUp) {}
-        void begin();
+        PortRead_MCP23S17(PortIOE& port, const uint8_t readPins) : port(port), readPins(readPins) {}
+        void begin(const uint8_t strobeOn);
         virtual uint8_t read();
 };
 #endif
diff --git a/src/PortWrite_MCP23S17.cpp b/src/PortWrite_MCP23S17.cpp
index f11ea99..81c461a 100644
--- a/src/PortWrite_MCP23S17.cpp
+++ b/src/PortWrite_MCP23S17.cpp
@@ -29,20 +29,20 @@ void PortWrite_MCP23S17::begin()
 }
 
 /*
-pin is bitwise, where pin being strobed is 1.
-strobe is HIGH or LOW (for active high or active low).
+strobePin is bitwise, where pin being strobed is 1.
+pinLogicLevel is HIGH or LOW.
 port.outputVal can be shared by LEDs.
 The functions does not reset the other pins so that they can be used for LEDs.
 */
-void PortWrite_MCP23S17::write(const uint8_t pin, const bool strobe)
+void PortWrite_MCP23S17::write(const uint8_t strobePin, const uint8_t pinLogicLevel)
 {
-    if (strobe == LOW)                          //if active low
+    if (pinLogicLevel == LOW)
     {
-        port.outputVal &= ~pin;                 //set pin output to low
+        port.outputVal &= ~strobePin;           //set strobePin output to low
     }
-    else                                        //if active high
+    else
     {
-        port.outputVal |= pin;                  //set pin output to high
+        port.outputVal |= strobePin;            //set strobePin output to high
     }
 
     writePort(port.num + 0x12, port.outputVal);  //set GPIO port pins for stobe and LEDs
diff --git a/src/PortWrite_MCP23S17.h b/src/PortWrite_MCP23S17.h
index 7d2ea90..bd3f7da 100644
--- a/src/PortWrite_MCP23S17.h
+++ b/src/PortWrite_MCP23S17.h
@@ -41,6 +41,6 @@ class PortWrite_MCP23S17 : public PortWrite
     public:
         PortWrite_MCP23S17(PortIOE& port) : port(port) {}
         void begin();
-        virtual void write(const uint8_t pin, const bool level);
+        virtual void write(const uint8_t pin, const uint8_t level);
 };
 #endif
diff --git a/unit_tests/PortRead_MCP23S17/PortRead_MCP23S17.ino b/unit_tests/PortRead_MCP23S17/PortRead_MCP23S17.ino
index 887129b..936a23f 100644
--- a/unit_tests/PortRead_MCP23S17/PortRead_MCP23S17.ino
+++ b/unit_tests/PortRead_MCP23S17/PortRead_MCP23S17.ino
@@ -9,6 +9,10 @@ http://arduino.stackexchange.com/questions/28792/reading-an-mcp23s17-i-o-expande
 */
 #include "PortIOE.h"
 #include "PortRead_MCP23S17.h"
+#include "Scanner_Port.h"
+
+const bool Scanner_Port::STROBE_ON = LOW;
+const bool Scanner_Port::STROBE_OFF = HIGH;
 
 const uint8_t PortIOE::ADDR = 0x20;             //MCP23S17 address, all 3 ADDR pins are grounded
 PortIOE portB(1, 0);
diff --git a/unit_tests/PortWrite_MCP23S17/PortWrite_MCP23S17.ino b/unit_tests/PortWrite_MCP23S17/PortRead_MCP23S17.ino
similarity index 100%
rename from unit_tests/PortWrite_MCP23S17/PortWrite_MCP23S17.ino
rename to unit_tests/PortWrite_MCP23S17/PortRead_MCP23S17.ino