void setup() {
  // put your setup code here, to run once:
  volatile char *dirf, *dirk, *dira;
  volatile char *outf, *ink, *outa;
  volatile long i, j;
  dirf = 0x30; dirk = 0x107; dira = 0x21;
  outf = 0x31; ink = 0x106; outa = 0x22;
  *dirf = 0x0F; *dirk = 0x00; *dira = 0xFF;
  while(1)
  {
    for(i=0; i<4; i++)
    {
      *outf = 1<<i;
      *outa = *ink;
      if(*ink != 0)
      {
        *outa = 1<<i;
        for(j=0; j<10000; j++);
        *outa = 0x00;
      }
    }
  }


}

void loop() {
  // put your main code here, to run repeatedly:
  char x = readKey();
  display(x);

}

char readKey() {
  char key = 0;
  for (int i = 0; i < 4; i++) {
    PORTB &= ~(1 << i); // Set column i low
    for (int j = 0; j < 4; j++) {
      if (!(PINB & (1 << j))) { // Check if row j is low
        key = i * 4 + j + 1; // Calculate key press
        return key;
      }
    }
    PORTB |= (1 << i); // Set column i high
  }
  return 0; // No key press
}

void display(char key) {
  switch (key) {
    case 1:
      PORTK = 0x3F; 
      break;
    case 2:
      PORTK = 0x06; 
      break;
    case 3:
      PORTK = 0x5B; 
      break;
    case 4:
      PORTK = 0x4F; 
      break;
    case 5:
      PORTK = 0x66; 
      break;
    case 6:
      PORTK = 0x6D; 
      break;
    case 7:
      PORTK = 0x07; 
      break;
    case 8:
      PORTK = 0x7F; 
      break;
    case 9:
      PORTK = 0x6F; 
      break;
    case 0:
      PORTK = 0x3F; 
      break;
  }
}