tast SBMM

 PORTC = 0x08;
  switch (PINB & 0x0F){
    case 0x01: UDR0 = '1'; break;
    case 0x02: UDR0 = '2'; break;
    case 0x04: UDR0 = '3'; break;
    case 0x08: UDR0 = 'A'; break;
  }

  PORTC = 0x04;
  switch (PINB & 0x0F){
    case 0x01: UDR0 = '4'; break;
    case 0x02: UDR0 = '5'; break;
    case 0x04: UDR0 = '6'; break;
    case 0x08: UDR0 = 'B'; break;
  }

  PORTC = 0x02;
  switch (PINB & 0x0F){
    case 0x01: UDR0 = '7'; break;
    case 0x02: UDR0 = '8'; break;
    case 0x04: UDR0 = '9'; break;
    case 0x08: UDR0 = 'C'; break;
  }

  PORTC = 0x01;
  switch (PINB & 0x0F){
    case 0x01: UDR0 = '*'; break;
    case 0x02: UDR0 = '0'; break;
    case 0x04: UDR0 = '#'; break;
    case 0x08: UDR0 = 'D'; break;
  }