// Pin definitions
int latchPin = 9; // Pin connected to ST_CP (Latch Pin) of 74HC595
int clockPin = 10; // Pin connected to SH_CP (Clock Pin) of 74HC595
int dataPin = 8;  // Pin connected to DS (Data Pin) of 74HC595
int potPin = A0;   // Pin connected to the middle pin of the potentiometer
int numOfRegisters = 2;  // Global variable for the number of shift registers (e.g., 2 registers = 16 LEDs)
int numLeds = numOfRegisters * 8; // Total number of LEDs controlled
int bitOrderPin = 12;

void setup() {
  // Set up the control pins for the 74HC595
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(bitOrderPin, INPUT_PULLUP);
  // Set up serial monitor for debugging (optional)
  Serial.begin(9600);
}

void loop() {
  // Read potentiometer value (0 to 1023)
  int potValue = analogRead(potPin);
  int bitOrderState = digitalRead(bitOrderPin);
  // Map the potentiometer value to a range of 0 to numLeds
  int numLedsOn = map(potValue, 0, 1023, 0, numLeds);

  // Display the mapped value on the LEDs using the specified bit order
  if (bitOrderState == HIGH) {
    updateLEDs(numLedsOn, LSBFIRST);
  }
  else {
    updateLEDs(numLedsOn, MSBFIRST);
  }
  // Optional: Print the number of LEDs on for debugging
  Serial.print("Potentiometer value: ");
  Serial.print(potValue);
  Serial.print(" | Number of LEDs ON: ");
  Serial.println(numLedsOn);


  // Small delay to smoothen the potentiometer reading
  delay(100);
}

//Function to update LEDs based on the number to be lit, using the global numOfRegisters
void updateLEDs(int numLedsOn, int bitOrder) {
  // Create a value with all bits for the LEDs to be on, and ensure it fits in the available space
  unsigned long long ledState = (1ULL << numLedsOn) - 1;  // Use a 64-bit variable to hold the LED states for larger numbers of LEDs
 
  // Start sending data to the shift registers
  digitalWrite(latchPin, LOW);  // Prepare to send data

  // Iterate through the registers and send data for each one
  if (bitOrder == MSBFIRST) {
    for (int i = numOfRegisters - 1; i >= 0; i--) {
      byte currentByte = (ledState >> (i * 8)) & 0xFF;  // Extract 8 bits for each register
      shiftOut(dataPin, clockPin, MSBFIRST, currentByte); // Send the byte to the shift register
    }
  } else {
    for (int i = 0; i < numOfRegisters; i++) {
      byte currentByte = (ledState >> (i * 8)) & 0xFF;  // Extract 8 bits for each register
      shiftOut(dataPin, clockPin, LSBFIRST, currentByte); // Send the byte to the shift register
    }
  }
  digitalWrite(latchPin, HIGH);  // Latch the data to the output pins
}