/*   we  make a commmon cathod for both display
     1st display is connect to PortF (A0 to A7)
     portf: direction register is 0x30;
           output data register is 0x31; 
      
     2nd display is conncet to PortK  (A8 to A15):
  is direction register is 0x107;
    output data register is 0108;  

 */

void setup() {
  // put your setup code here, to run once:
   volatile char *dir;
   dir=0x30;   //  for  display 1 portf direction register 
   *dir=0xff;  // set all pin off

   dir = 0x107; //   for  display 2 portk direction register 
}

void loop() {
  // put your main code here, to run repeatedly:
  volatile char *out;
  out = 0x31; // for display 1 data register 
  *out= 0x5b;   // output value is 2

  out = 0x108; // for display 2 data register 
  *out = 0x6D; // output value is 5 
}