#include "PortWrite_MCP23S17.h"

/* begin() is called from Scanner_IOE::begin().
Initiates SPI bus and configures port pins to output.
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 PortWrite_MCP23S17::begin()
{
    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.

    transfer(port.DEVICE_ADDR << 1, port.num, 0); //configure port direction (port.num) to output (0)
}

/* write() sets pin output to logicLevel.
pin is bit pattern, where pin being set is 1.
logicLevel is HIGH or LOW.
write() does not overwrite the other pins.
*/
void PortWrite_MCP23S17::write(const uint8_t pin, const bool logicLevel)
{
    if (logicLevel == LOW)
    {
        port.outputVal &= ~pin;                 //set pin output to low
    }
    else
    {
        port.outputVal |= pin;                  //set pin output to high
    }

    transfer(port.DEVICE_ADDR << 1, port.num + 0x12, port.outputVal); //set GPIO port to outputVal
}