// Define connection to 74HC595
int Latch_Pin = 10;  // Pin connected to ST_CP (Latch pin) of 74HC595
int Clock_Pin = 11;  // Pin connected to SH_CP (Clock pin) of 74HC595
int Data_Pin = 12;   // Pin connected to DS (Data pin) of 74HC595

byte LEDs = 0x24;    // Variable to hold the current LED pattern (8 bits)
// 0x00	00000000	0x00	All LEDs OFF
// 0xFF	11111111	0xFF	All LEDs ON
// 0xAA	10101010	0xAA	Alternate LEDs ON
// 0x55	01010101	0x55	Another Alternate LEDs ON
// 0x24	00100100	0x24	LEDs at positions 2 & 5 ON

void setup() {
  Serial.begin(9600);           // Initialize serial communication at 9600 baud
  pinMode(Latch_Pin, OUTPUT);   // Set Latch_Pin as an output
  pinMode(Clock_Pin, OUTPUT);   // Set Clock_Pin as an output
  pinMode(Data_Pin, OUTPUT);    // Set Data_Pin as an output
}

void loop() {
  if (Serial.available()>0){ // Check id there is also data avaliable in the Serial buffer
    char input = Serial.read(); // Read the input character
    if(input == '0'){
      LEDs = 0x00; // All LEDs OFF
    }
  else if(input == '1'){
    LEDs = 0xFF; // All LEDs ON
  }
  else if (input == 'A'){
    LEDs = 0xAA; // Alternate LEDs ON
  }
  else if(input == 'B'){
    LEDs = 0x55; // Another alternet LEDs ON
  }
  else if (input == 'C'){
    LEDs == 0x24; // LEDs are position 2 & 5 ON
  }
  }
  digitalWrite(Latch_Pin, LOW); // Pull Latch_Pin LOW to prepare for data transfer
  Serial.print("LED Pattren = "); // Print LEDs Pattern  to serial monitor
  Serial.println(LEDs, HEX);             // Print the current LED pattern (in decimal format)

  shiftOut(Data_Pin, Clock_Pin, MSBFIRST, LEDs); // Send data to the shift register

  digitalWrite(Latch_Pin, HIGH); // Pull Latch_Pin HIGH to latch the data and update LEDs
  delay(100);                    // Delay for 100 ms before the next iteration
}