update keybrd_4c_split_keyboard_with_IOE.ino

src/PortMCP23S17.cpp

@@ -1,36 +1,34 @@
 #include "PortMCP23S17.h"
 
 /* transfer() writes data to registerAddr, reads portSate from registerAddr, and returns portState.
+
+MCP23S17 SPI interface is 10 MHz max.
+The electrical limitation to bus speed is bus capacitance and the length of the wires involved.
+Longer wires require lower clock speeds. 
 */
 uint8_t PortMCP23S17::transfer(const uint8_t command, const uint8_t registerAddr,
         const uint8_t data)
 {
     uint8_t portState;                          //bit pattern
 
+    SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz
     digitalWrite(SS, LOW);                      //enable Slave Select
       SPI.transfer(command);                    //write or read command
       SPI.transfer(registerAddr);               //register address to write data to
       portState = SPI.transfer(data);           //write data, read portState
     digitalWrite(SS, HIGH);                     //disable Slave Select
+    SPI.endTransaction();
 
     return portState;
 }
 
-/* begin() is called from Scanner_IOE::begin().
+/* begin() is called from Scanner_IOE::begin().  Initiates SPI bus.
-Initiates SPI bus and configures I/O pins for read and write.
-
-MCP23S17 SPI interface is 10 MHz max.
-The electrical limitation to bus speed is bus capacitance and the length of the wires involved.
-Longer wires require lower clock speeds. 
 */
 void PortMCP23S17::beginProtocol()
 {
     pinMode(SS, OUTPUT);                        //configure controller's Slave Select pin to output
     digitalWrite(SS, HIGH);                     //disable Slave Select
     SPI.begin();
-    SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz
-    //SPI.endTransaction() not called to release SPI bus because keyboard only has one SPI device
-    //if two IOEs are used, move beginTransaction() endTransaction() to write() read() functions
 }
 
 /* begin() is called from Scanner_IOE::begin().

src/PortMCP23S17.h

@@ -6,8 +6,8 @@
 #include <PortInterface.h>
 
 /*
-readPins are connected to matrix col
+write pins are connected to matrix Row (strobe pin) or LED.
-write pin is connected to matrix Row (strobe pin) or LED.
+readPins are connected to matrix column to read which keys are pressed.
 
 Slave Select is hardcoded to Arduino Pin 10.
 Arduino Pin 10 avoids the speed penalty of digitalWrite.
@@ -20,9 +20,9 @@ MCP23S17 datasheet identifies ports by letters, while class PortMCP23S17 uses po
 readPins parameter configures port's pins.
 
 Example instantiation:
-    const uint8_t Port_MCP23S17::DEVICE_ADDR = 0x20; //MCP23S17 address, all 3 ADDR pins grounded
+    const uint8_t IOE_ADDR = 0x20;              //MCP23S17 address, all 3 ADDR pins are grounded
-    Port_MCP23S17 portB(1, 0);                  //all pins are set to output for strobes and LEDs
+    Port_MCP23S17 portB(IOE_ADDR, 1, 0);        //all pins are set to output for strobes and LEDs
-    Port_MCP23S17 portA(0, 1<<0 | 1<<1 );       //1 pins are set to input for reading,
+    Port_MCP23S17 portA(IOE_ADDR, 0, 1<<0 | 1<<1 ); //first two pins are set to input for reading,
                                                 //remaining pins can be used for LEDs
 
 Diode orientation
@@ -39,7 +39,7 @@ class PortMCP23S17 : public PortInterface
         const uint8_t deviceAddr;
         const uint8_t portNum;                  //port identification number
         uint8_t outputVal;                      //bit pattern for strobe and LEDs
-        const uint8_t readPins;                 //bits, IODIR 0=output, 1=input
+        const uint8_t readPins;                 //bit pattern, IODIR 0=output, 1=input
         uint8_t transfer(const uint8_t command, const uint8_t registerAddr, const uint8_t data);
     public:
         PortMCP23S17(const uint8_t deviceAddr, const uint8_t portNum, const uint8_t readPins)

tutorials/keybrd_4c_split_keyboard_with_IOE/keybrd_4c_split_keyboard_with_IOE.ino

@@ -21,9 +21,7 @@ This layout table shows left and right matrices:
 #include <Scanner_uC.h>
 
 //right matrix
-#include <PortIOE.h>
+#include <PortMCP23S17.h>
-#include <PortWrite_MCP23S17.h>
-#include <PortRead_MCP23S17.h>
 #include <Scanner_IOE.h>
 
 // ============ SPEED CONFIGURATION ============
@@ -33,37 +31,28 @@ ScanDelay scanDelay(9000);
 Left matrix rows work the same as the ones in keybrd_2_single-layer.ino
 */
 uint8_t readPins[] = {14, 15};
-const uint8_t READPIN_COUNT = sizeof(readPins)/sizeof(*readPins);
+const uint8_t readPinCount = sizeof(readPins)/sizeof(*readPins);
 
-Scanner_uC scanner_L(LOW, readPins, READPIN_COUNT);
+Scanner_uC scanner_L(LOW, readPins, readPinCount);
 
 /* =============== RIGHT SCANNER ===============
 The right matrix is scanned by an I/O expander.
-
+The MCP23S17 address is set by grounding or powering pins.
-The I/O expander device address is configured by hardware pins.
-DEVICE_ADDR is a static variable of class PortIOE.
 */
-const uint8_t PortIOE::DEVICE_ADDR = 0x20;      //MCP23S17 address with all 3 ADDR pins are grounded
+const uint8_t IOE_ADDR = 0x20;                  //MCP23S17 address, all 3 ADDR pins are grounded
 
 /*
-port_B stobes the row while port_A reads the colums.
+Normally all strobe pins are on one port, and all the read pins are on the other port.
-
+In this example, portB stobes the row while portA reads the colums.
-port_A is assigned port identification number 0.
+PortMCP23S17 constructor parameters are: deviceAddr, portNum, readPins
-port_A is assigned to portRead, which reads port_A pins 0 and 1.
+readPins is a bit pattern, where 0=output, 1=input.
+In portA, the first two pins are set to input for reading.
 "<<" (bit shift left) and "|" (OR) are bitwise operators.
 Pin numbers to be read are to the right of "1<<" and delimited by "|".
 */
-PortIOE port_A(0);
+PortMCP23S17 portA(IOE_ADDR, 0, 1<<0 | 1<<1 );
-PortRead_MCP23S17 portRead(port_A, 1<<0 | 1<<1 );
+PortMCP23S17 portB(IOE_ADDR, 1, 0);
-
+Scanner_IOE scanner_R(LOW, portB, portA);
-/*
-port_B is assigned port identification number 1.
-port_B is assigned to portWrite.
-*/
-PortIOE port_B(1);
-PortWrite_MCP23S17 portWrite(port_B);
-
-Scanner_IOE scanner_R(LOW, portWrite, portRead);
 
 // =================== CODES ===================
 Code_Sc s_a(KEY_A);

tutorials/keybrd_5b_LED_on_IOE/keybrd_5b_LED_on_IOE.ino

@@ -34,7 +34,7 @@ This layout table shows left and right matrices:
 // ============ SPEED CONFIGURATION ============
 ScanDelay scanDelay(9000);
 
-// ================ LEFT ===============
+// ================= LEFT PINS =================
 // ---------------- LEFT SCANNER ---------------
 uint8_t readPins[] = {14, 15};
 const uint8_t readPinCount = sizeof(readPins)/sizeof(*readPins);
@@ -44,7 +44,7 @@ Scanner_uC scanner_L(LOW, readPins, readPinCount);
 // ----------------- LEFT LEDs -----------------
 LED_uC LED_CapsLck(21);
 
-// =============== RIGHT ===============
+// ================ RIGHT PINS =================
 // --------------- RIGHT SCANNER ---------------
 const uint8_t IOE_ADDR = 0x20;                  //MCP23S17 address, all 3 ADDR pins are grounded
 PortMCP23S17 portA(IOE_ADDR, 0, 1<<0 | 1<<1 );  //for read and LED

tutorials/tutorial_4c_split_keyboard_with_IOE.md

@@ -35,7 +35,8 @@ The MCP23S17 with all address pins grounded has an device address of 0x20.
 The MCP23S17's /RESET pin is connected to VDD.
 
 The MCP23S17 I/O expander has two ports.  Each port has eight pins.
-Port B is connected to the matrix's rows.  Port A is connected to the matrix's columns.
+Port B is connected to the matrix's rows.
+Port A is connected to the matrix's columns.
 
 Building a split keyboard with I/O Expander
 -------------------------------------------