/* Controling a 555 Timer IC Square Wave Generator via an SPI-based Pot
by Sebastian Tomczak
25 June 2007, Adelaide, Australia
*/


#define SLAVESELECT 10//ss
#define SPICLOCK  13//sck
#define DATAOUT 11//MOSI
#define DATAIN 12//MISO

// command bytes
byte cmdWritePot1 =      B00010001; // write data to pot 1
byte cmdWritePot2 =      B00010010; // write data to pot 1


byte serIn1;
byte serIn2;


void spi_transfer(byte data)
{
  SPDR = data;                    // Start the transmission
  while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
  {
  };
}


// Setup Function Begins Here

void setup()
{
  Serial.begin(57600);
  byte clr;
  pinMode(DATAOUT,OUTPUT);
  pinMode(SPICLOCK,OUTPUT);
  pinMode(SLAVESELECT,OUTPUT);
  digitalWrite(SLAVESELECT,HIGH); //disable device

  SPCR = B01010000;

  /*
  SPCR bits:
   7: SPIEE - enables SPI interrupt when high
   6: SPE - enable SPI bus when high
   5: DORD - LSB first when high, MSB first when low
   4: MSTR - arduino is in master mode when high, slave when low
   3: CPOL - data clock idle when high if 1, idle when low if 0
   2: CPHA - data on falling edge of clock when high, rising edge when low
   1: SPR1 - set speed of SPI bus
   0: SPR0 - set speed of SPI bus (00 is fastest @ 4MHz, 11 is slowest @ 250KHz)
   */


  clr = SPSR;
  clr = SPDR;
  delay(10);
}

void write_pot_1_1(byte potValue1_1)
{
  // spi pot chip 1 
  digitalWrite(SLAVESELECT,LOW); // enable chip 1
  // set value for pot A
  spi_transfer(cmdWritePot1); // command byte out to select pot and init write
  spi_transfer(potValue1_1); // 8 bit pot value
  digitalWrite(SLAVESELECT,HIGH); // disable spi pot

}

void write_pot_1_2(byte potValue1_2)
{
  // spi pot chip 1 
  digitalWrite(SLAVESELECT,LOW); // enable chip
  // set value for pot B
  spi_transfer(cmdWritePot2); // command byte out to select pot and init write
  spi_transfer(potValue1_2); // 8 bit pot value
  digitalWrite(SLAVESELECT,HIGH); // disable spi pot

}




// Main Loop Begins Here

void loop()
{

  if(Serial.available() > 1) {
    serIn1 = Serial.read();
    serIn2 = Serial.read();
    write_pot_1_1(serIn1);
    write_pot_1_2(serIn2);
  }

}