// Standard Arduino code to read analog value from A0, compare with 500, and control LED

const int ledPin = 13; // Pin where the led is connected

void setup() {
  // Start the serial communication
  Serial.begin(9600);

  // Initialize the LED pin as an output
  pinMode(ledPin, OUTPUT);

}

void loop() {
  // Read the analog value from pin A0
  int analogValue = analogRead(A0);

  // Split the analog value into lower and higher bytes
  uint8_t lowerByte = analogValue & 0xFF; // Lower 8 bits of the analog value
  uint8_t higherByte = (analogValue >> 8) & 0x03; // Higher 2 bits of the analog value

  // Inline assembly to load the lowerByte and higherByte into r24 and r25 respectively
  asm volatile(
    "mov r24, %0 \n\t"
    "mov r25, %1 \n\t"
    : // No output operands
    : "r" (lowerByte), "r" (higherByte) // Input operands
    : "r24", "r25" // Clobbered registers
  );

  // Variable to store the result of the comparison
  uint8_t result;

  // Inline assembly to compare combineValue with 500 (0x01F4) and set result
  asm volatile(
    "cpi r25, 1 \n\t"
    "brlo less_than_500 \n\t"
    "brne greater_or_equal_500 \n\t"
    
    "cpi r24, 244 \n\t"
    "brlo less_than_500 \n\t"

    "greater_or_equal_500: \n\t"
    "ldi r18, 1 \n\t"
    "rjmp end_compare \n\t"

    "less_than_500: \n\t"
    "ldi r18, 0 \n\t"

    "end_compare: \n\t"
    "mov %0, r18 \n\t"
    : "=r" (result)
    : // No input operands
    : "r18", "r24", "r25" // Clobbered registers
  );

  //  Control the LED based on the comparison result
  if (result) {
    // Turn the LED on if the value is above or equal to 500
    digitalWrite(ledPin, HIGH);
  } else {
    // Turn the LED off if the value is less than 500
    digitalWrite(ledPin, LOW);
  }

  // Print the analog value to the serial monitor
  Serial.println(analogValue);

  // Add small delay to stablize the reading
  delay(100);
}