#include <Arduino.h>

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  Serial.begin(9600);

  // Set all PORTB pins as output
  DDRB = 0xFF;

  // Set all PORTD pins as input with pull-up resistors
  DDRD = 0x00;
  PORTD = 0x0F;
}

void loop() {
  // Read the input from PORTD
  uint8_t portd_value = PIND;

  // Shift right by 2 bits
  portd_value = portd_value >> 2;
  
  asm volatile ( 
    "ldi r21, 0x00\n"          // Load immediate value 0x00 into register R21
    "lds r20,  portd_value\n"          // Load immediate value 0x45 into register R20
    "ldi r16, 0x01\n"
    "cp r20, r21" 
    "brne next1\n"  
    "jmp over"             // Branch to 'next' if the carry flag is clear            
  "next1: add r21, 1" 
   "lsl r16\n" 
    "cp r20, r21" 
   "brne next2\n"              // Branch to 'next' if the carry flag is clear
     "jmp over"    
  "next2: add r21, 1"    
   "lsl r16\n"   
    "cp r20, r21" 
  "breq over\n"                // Branch to 'next' if the carry flag is clear
    "lsl r16\n" 
  "over: lsr r16" 
    "sts %0, r16\n"            // Store the value of R20 into the variable x         // Store the value of R21 into the variable y
    : "=m" (portd_value)       // Output operands: x and y are memory locations to be written to
    :                          // No input operands
    : "r20", "r21", "r16"      // Clobbered registers: R20, R21, R16 will be used and modified
  );


  // Print the value to the serial monitor
  Serial.println(portd_value);
  
  // Output the value to PORTB
  PORTB = portd_value;

  // Wait for a second before the next loop iteration
  delay(10);
}