//#include <SoftwareSerial.h>
//SoftwareSerial serial (5, 1);

#include <Arduino.h>

int  i;
unsigned int x, y;
float accum, fout, fval = 0.001;    // these are variables for a simple low-pass (smoothing) filter - fval of 1 = no filter - .001 = max filter
long threshold = 0;

int main() {  
  //serial.begin(9600);

  // sender PA7
  // receiver PB2
  // pot PB0

  DDRA = 0b10000000;
  DDRB = 0b00000000;
  PORTA = 0b00000000;
  PORTB = 0b00000001;  

  // Threshold calibration
  for (short i = 0; i < 10; i++) {
    long max;
    y = 0;
    x = 0;
    for (short i = 0; i < 4; i++) {
      // LOW-to-HIGH transition
      PORTA |= 0b10000000; // Sender HIGH
      while ((PINB & 0b0000100) != 0b00000100 ) { // loop while receiver is LOW
        x++;
      }
      delay(1);

      //  HIGH-to-LOW transition
      PORTA &= 0b01111111; // Sender LOW       
      while((PINB & 0b00000100) != 0b00000000 ) { // loop while receiver is HIGH
        y++;  
      }
      delay(1);
    }
    max = (x > y ? x : y);
    threshold = (threshold > max ? threshold : max);
  }

/*
  Serial.print("T: ");
  Serial.println(threshold);
  Serial.print('\n');
*/
  while (true) {
    y = 0;
  x = 0;

  for (short i = 0; i < 4; i++) {
    // LOW-to-HIGH transition
    PORTA |= 0b10000000; // Sender HIGH
    while ((PINB & 0b00000100) != 0b00000100 ) { // loop while receiver is LOW
      x++;
    }
    delay(1);
    
    //  HIGH-to-LOW transition
    PORTA &= 0b01111111; // Sender LOW       
    while((PINB & 0b00000100) != 0b00000000 ) { // loop while receiver is HIGH
      y++;  
    }
    delay(1);
  
  fout =  (fval * (float)x) + ((1-fval) * accum);  // Easy smoothing filter "fval" determines amount of new data in fout
  accum = fout;  
  }
/*
  // Check on threshold
  if (x > threshold && y > threshold) {    
    serial.println("A");    
  } else {
    serial.println("!A");    
  }
  serial.print(x);
  serial.print(" - ");
  serial.println(y);
  delay(1500);
  
  if ( (PINB & 0b00000001) != 0b00000001 ) {
    serial.println("P");
  } else {
    serial.println("!P");
  }
  }
  */
}
}