// recievercode for mega

int wW = 0;
int xX = 0;
int yY = 0;
int sum;
int state11;
int state12;
int state;
int x = 0;
int a;
int b;
int c;
int d;
int A = 0;
int y;

void setup() 
{
 pinMode(18,INPUT_PULLUP);
 pinMode(2,INPUT_PULLUP);
pinMode(3,INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(2),interruptpin3,CHANGE);
attachInterrupt(digitalPinToInterrupt(3),interruptpin2,CHANGE);
attachInterrupt(digitalPinToInterrupt(18),interruptpin18,CHANGE);
Serial.begin(9600);
}

void loop () 
{ 



if(A == 0 && x == 0 )
{  
 a = state;
 x = 1;    
}
if(A == 1  ) 
{
 if( x == 1)
 {  
b = state;
x = 2;
 }
  if(state != b && x == 2) 
  {
c = state;
 if( c == 2 )//units 0 - 3
 { 
if(a == 0 && b == 0 ||  a == 1 && b == 0 || a == 0 && b == 1 || a == 1 && b == 1)
{
 wW = (b*2 + a);
  d = 1; 
}
 }
   if(c == 0)// units 4 - 9 
 { 
if(a == 0 && b == 2 || a == 1 && b == 2 || a == 2 && b == 2 || a == 1 && b == 3 || a == 2 && b == 3 || a == 3 && b == 3)
{
 wW = (b*2 + a);
 d = 1; 
}
 }
   if( c == 3)//tens  0 - 3)
 { 
if(a == 0 && b == 0 || a == 1 && b == 0 || a == 0 && b == 1  || a == 1 && b == 1)
{
 xX = (b*2 + a);
  d = 2; 
}
 }
  if( c == 1)// tens 4 - 9 
 { 
if(a == 0 && b == 2 || a == 1 && b == 2 || a == 2 && b == 2 || a == 1 && b == 3 || a == 2 && b == 3 || a == 3 && b == 3 )
{
 xX = (b*2 + a);
  d = 2;  
}
 }
   if( c == 1)// hunderds 0 - 1 
 { 
if(a == 0 && b == 0 || a == 1 && b == 0)
{
 yY = (b*2 + a);
  d = 3;  
}
 }
   if( c == 0)// hunderds 2 - 3
 { 
if(a == 0 && b == 1 || a == 1 && b == 1)
{
 yY = (b*2 + a);
  d = 3; 
}
 }
   if( c == 3)//hunderds  4 -  6 
 { 
if(a == 0 && b == 2 || a == 1 && b == 2 || a == 2 && b == 2)
{
 yY = (b*2 + a);
  d = 3; 
}
 }
    if( c == 2)//hunderds  7 - 9 
 { 
if(a == 1 && b == 3 || a == 2 && b == 3 || a == 3 && b == 3)
{
 yY = (b*2 + a);
  d = 3; 
}
 }
if(c == 2 && b == 0 || c == 2 && b == 1 || c == 0 && b == 2 || c == 0 && b == 3 )//when the units are recieved,
 {
  sum = (yY*100)+ (xX*10) + wW;//calculate sum
 }
  Serial.print("sum = ");
Serial.println(sum);
 a = 5;
 b = 5;
 c = 5;
x = 0;
 }
}
}
void interruptpin18()          
{  
 A = digitalRead(18);//controlline
 state11 = digitalRead(2);// dataline1
 state12 = digitalRead(3);// dataline2
 state = (state11*2) + state12;                 
}
void interruptpin2()        
{ 
  A = digitalRead(18);//controlline 
 state11 = digitalRead(2);// dataline1
 state12 = digitalRead(3);// dataline2 
 state = (state11*2) + state12;
}
void interruptpin3()         
{  
  A = digitalRead(18);//controlline
 state12 = digitalRead(3);// dataline2
 state11 = digitalRead(2);// dataline1 
 state = (state11*2) + state12;                     
}