void setup() {
  // put your setup code here, to run once:
  volatile char *PORT_F_DIR_REG = (char*) 0x30;
  *PORT_F_DIR_REG = 0xFF;
  volatile char *PORT_K_DIR_REG = (char*) 0x107;
  *PORT_K_DIR_REG = 0xFF;
  volatile char *PORT_A_DIR_REG = (char*) 0x21;
  *PORT_A_DIR_REG = 0x00;

}

void loop() {
   
  // put your main code here, to run repeatedly:
  volatile char combinations[16] = {
    0x11,
    0x21,
    0x41,
    0x81,
    0x12,
    0x22,
    0x42,
    0x82,
    0x14,
    0x24,
    0x44,
    0x84,
    0x18,
    0x28,
    0x48,
    0x88
  };

    volatile char sevseg[16] = {
    0x06,
    0x5B,
    0x4F,
    0x77,
    0x66,
    0x6D,
    0x7D,
    0x7C,
    0x07,
    0x7F,
    0x6F,
    0x39,
    0x79,
    0x3F,
    0x79,
    0x5E
  };

  volatile char *PORT_F_DATA_REG = (char*) 0x31;
  volatile char *PORT_K_DATA_REG = (char*) 0x108;
  volatile long i,j,k;
  volatile char *PORT_A_INPUT_REG = (char*) 0x20;
  volatile char input_data;
 
  for (i = 0; i < 4; i++){
    *PORT_F_DATA_REG = (1 << i);
    input_data = *PORT_A_INPUT_REG;
    if (input_data !=0) {
      input_data |= *PORT_F_DATA_REG;
      for(j = 0; j<16; j++) {
        if((input_data & combinations[j]) == combinations[j]){
          *PORT_K_DATA_REG = sevseg[j];
          for(k = 0; k < 20000; k++);
        }
      }
    }

  }
}