Port_MCP23S17.h

#ifndef PORT_MCP23S17_H
#define PORT_MCP23S17_H
#include <Arduino.h>
#include <inttypes.h>
#include <SPI.h>
#include "PortInterface.h"

/* Port_MCP23S17
write pins are connected to matrix Row (strobe pin) or LED.
readPins are connected to matrix column to read which keys are pressed.

slaveSelect is Arduino-pin number connected to pin 11 (CS a.k.a. SS).

Instantiation
 ------------
MCP23S17 datasheet identifies ports by letters, while class Port_MCP23S17 uses portNum
    for port A, use portNum=0
    for port B, use portNum=1
readPins parameter configures port's pins.

Example instantiation:
    const uint8_t IOE_ADDR = 0x20;              //MCP23S17 address, all 3 ADDR pins are grounded
    Port_MCP23S17 portB(IOE_ADDR, 1, 0);        //all pins are set to output for strobes and LEDs
    Port_MCP23S17 portA(IOE_ADDR, 0, 1<<0 | 1<<1 ); //pin 0 and pin 1 are set to input for reading,
                                                //remaining pins can be used for LEDs

Diode orientation
 ----------------
Diode orientation is explained in keybrd_library_user_guide.md > Diode orientation

MCP23S17 data sheet
 ------------------
 http://www.onsemi.com/pub_link/Collateral/MCP23S17-D.PDF
*/
class Port_MCP23S17 : public PortInterface
{
    private:
        const uint8_t slaveSelect;              //controller-pin number
        const uint8_t deviceAddr;
        const uint8_t portNum;                  //port identification number
        uint8_t outputVal;                      //bit pattern for strobe and LEDs
        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:
        Port_MCP23S17(const uint8_t slaveSelect, const uint8_t deviceAddr, const uint8_t portNum, const uint8_t readPins)
            : slaveSelect(slaveSelect), deviceAddr(deviceAddr), portNum(portNum), outputVal(0), readPins(readPins) {}
        void beginProtocol();
        void begin(const uint8_t activeState);
        virtual void writeLow(const uint8_t pin);
        virtual void writeHigh(const uint8_t pin);
        virtual uint8_t read();
};
#endif