// Clock Reader, auto-synchronized
// Next bit encoding depends on previous bit color
// State encoding :
// Present state     Encoding       Next State
//           0      Yellow = 0      2
//           0      Grey   = 1      1
//           1      Black  = 0      0
//           1      Yellow = 1      2
//           2      Black  = 0      0
//           2      Grey   = 1      1
 

// Threshold between black and grey
#define BG 42
// Threshold between grey and yellow
#define GJ 51

#define Hysteresis 2

#define Center 3

#define Light SENSOR_2
#define CardPresent SENSOR_1

int State;
int Value;


task main()
{
  SetSensor(Light,SENSOR_LIGHT);
  SetSensor(CardPresent,SENSOR_TOUCH);
  while (true)
  {
    until (CardPresent==1);
    OnFwd(OUT_C);
    GetValue();
  }
}

void GetValue()
{
  Value = 0;
  State = 0;
  until (Light < BG - Hysteresis); // First plate is black
  Wait(Center);
  repeat (15)
  {
    Value *= 2;
    if (State == 0)
    {
	until (Light > BG + Hysteresis);
	Wait(Center);
	if (Light > GJ)
	{
	  State = 2;
	}
	else
	{
	  Value += 1;
	  State = 1;
      }
    }

    else if (State == 1)
    {
	until ((Light < BG - Hysteresis)|| (Light > GJ + Hysteresis));
	Wait(Center);
	if (Light < BG)
	{
	  State = 0;
	}
	else
	{
	  Value += 1;
	  State = 2;
      }
	
    }
    else if (State == 2)
    {
	until (Light < GJ - Hysteresis);
	Wait(Center);
	if (Light < BG)
	{
	  State = 0;
	}
	else
	{
	  Value += 1;
	  State = 1;
      }
	
    }
  }
  Wait(50);
  Float(OUT_C);  
}