// void setup() {
//   // put your setup code here, to run once:
//   volatile char *dirF, *dirK, *dirA,*dirC;
//   dirF=0x30, dirK=0x107,dirA=0x21,dirC=0x27;
//   *dirF=0xFF, *dirK=0x00,*dirA=0xFF,*dirC=0xFF;

//  volatile char *outF,*inK, *outA, *outC;
//   outF=0x31, inK=0x106, outA=0x22 , outC=0x28 ;
 
//   // *outA=0x0F;
  
//   volatile long i,j;
//   while(1){
//     for( i=0; i<4; i++){
//       *outF=1 << i;
//       if(*inK !=0){
//       *outA=*inK;
//        *outC=1 <<i;
//        for(j=0; j<100000;j++);
//       }
//       *outC=0;
//       *outA=0;
//     }
//   }

// }

// void loop() {
//   // put your main code here, to run repeatedly:
  

// }
#include <math.h>
void setup() {
  // put your setup code here, to run once:
  volatile char *dirF, *dirK, *dirA,*dirC;
  dirF=0x30, dirK=0x107,dirA=0x21,dirC=0x27;
  *dirF=0xFF, *dirK=0x00,*dirA=0xFF,*dirC=0xFF;

 volatile char *outF,*inK, *outA, *outC;
  outF=0x31, inK=0x106, outA=0x22 , outC=0x28 ;
 Serial.begin(9600);
  // *outA=0x0F;
  volatile int col,row;
  char keys[4][4] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'.', '0', '=', '/'}
};
  
  
  volatile long i, j;

   while(1) {
    for(i = 0; i < 4; i++) {
      *outF = 1 << i;
      
      if(*inK != 0) {
        col = *inK;
        row = 1 << i;
        *outC = row;
        *outA = col;
        Serial.print(keys[int(log(row) / log(2))][int(log(col) / log(2))]);
       
        // Debounce delay for stable key press detection
        delay(50);
        
        // Wait for key release
        while (*inK != 0);
        
        // Turn off LEDs once key is released
        *outC = 0;
        *outA = 0;
      }
      delay(10); // Short delay between each iteration
    }
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  

}