/*
 
  Code to test MCP23S08 SPI B-bit I/O expander

  See:
     
     <http://code.rancidbacon.com/LearningAboutArduinoMCP23S08>

     <http://www.arduino.cc/en/Tutorial/SPIEEPROM>

*/

// Define SPI-related pins
#define PIN_DATA_OUT 11 // MOSI (Master Out / Slave In)
#define PIN_DATA_IN  12 // MISO (Master In / Slave Out)
#define PIN_SPI_CLOCK  13 // SCK (Serial Clock) 
#define PIN_SLAVE_SELECT 10 // SS (Slave Select)


void setup () {
  Serial.begin(9600);
  Serial.println("Setup enter...");

  Serial.print("SPCR: "); Serial.println(SPCR, BIN);

  // Configure SPI
  //   Configure I/O pins
  pinMode(PIN_DATA_OUT, OUTPUT);
  pinMode(PIN_DATA_IN, INPUT);
  pinMode(PIN_SPI_CLOCK, OUTPUT);
  pinMode(PIN_SLAVE_SELECT, OUTPUT);
  
  digitalWrite(PIN_SLAVE_SELECT, HIGH); // Disable slave
  
  //    Configure SPI Control Register (SPCR) (All values initially 0)
  //     Bit  Description
  //       7  SPI Interrupt Enable    -- disable  (SPIE --> 0)
  //       6  SPI Enable              -- enable   (SPE  --> 1)
  //       5  Data Order              -- MSB 1st  (DORD --> 0) (Slave specific)
  //       4  Master/Slave Select     -- master   (MSTR --> 1)
  //       3  Clock Polarity          --          (CPOL --> 0) (Slave specific) ("Mode")
  //       2  Clock Phase             --          (CPHA --> 0) (Slave specific)
  //       1  SPI Clock Rate Select 1 -- }        (SPR1 --> 0) 
  //       0  SPI Clock Rate Select 0 -- } fOSC/4 (SPR0 --> 0) ("Fastest" but see SPI2X in SPSR)
  SPCR = (1<<SPE)| (1<<MSTR);

  Serial.print("SPCR: "); Serial.println(SPCR, BIN);
  
  // Clear previous data and status (TODO: Determine if necessary/better way.)
  // (Based on Playground SPI example.)
  byte dummy;
  dummy = SPSR;
  dummy = SPDR;
  delay(10);
    
  // Serial.println((1 << SPIF), BIN);
  
# define SLAVE_ADDRESS_BASE    (B01000 << 3)
# define SLAVE_ADDRESS_BIT_A1  (0 << 2)  // TODO: Allow non-zero and define constants 
# define SLAVE_ADDRESS_BIT_A0  (0 << 1)  // TODO: Allow non-zero and define constants 
# define SLAVE_ADDRESS         (SLAVE_ADDRESS_BASE|SLAVE_ADDRESS_BIT_A1|SLAVE_ADDRESS_BIT_A0)

# define CONTROL_BIT_READ 1

# define REG_IODIR 0x00
# define REG_IOPOL 0x01

# define REG_GPIO 0x09

        
  byte deviceOpcode = 0;
  
  deviceOpcode = (SLAVE_ADDRESS | CONTROL_BIT_READ);
  
  Serial.println(deviceOpcode, BIN);

  digitalWrite(PIN_SLAVE_SELECT, LOW); // Enable slave
  spi_transfer(deviceOpcode);
  // spi_transfer(REG_IODIR);  // The register we want to read
  // spi_transfer(REG_IOPOL);  // The register we want to read
  spi_transfer(REG_GPIO);  // The register we want to read
  
  // int data; // Correct type?
  byte data; // Correct type?
  //unsigned long data; // Correct type?
  data = spi_transfer(0xFF); // Transfer dummy byte to get response
  digitalWrite(PIN_SLAVE_SELECT, HIGH); // Disable slave
  
  Serial.print("Response: ");
  Serial.println(data, BIN);
        
  Serial.println("Setup exit...");
}


// From Playground
char spi_transfer(volatile char data)
{
  SPDR = data;                    // Start the transmission
  while (!(SPSR & (1<<SPIF)))     // Wait for the end of the transmission
  {
  };
  return SPDR;                    // return the received byte
}




void loop() {
}