// Define pin numbers
const int switchPin1 = 8;  // Switch Pin for decreasing the frequency
const int switchPin2 = 7;  // Switch pin for increasing the frequency
const int ledPin = 6;      // LED pin

// Define variables
int frequency = 1000;  // Initial frequency (in milliseconds)
unsigned long previousMillis = 0; // Variable to store previous time

void setup() {
  // Setting the LED pin as output
  pinMode(ledPin, OUTPUT);

  // Setting both switch pins as inputs with interupts             
  pinMode(switchPin1, INPUT_PULLUP);
  pinMode(switchPin2, INPUT_PULLUP);
}

void loop() {
  // Read the state of switch 1
  if (digitalRead(switchPin1) == LOW) {
    frequency = frequency*2; // Decrease the frequency by multiplying by 2
    delay(200); // Debounce delay
  }

  // Read the state of switch 2
  if (digitalRead(switchPin2) == LOW) {
    frequency = frequency/2; // Increase the frequency by dividing by 2
    delay(200); // Debounce delay
  }

  // Range of frequencies
  if (frequency < 125) {
    frequency = 125; // Maximum frequency (8 Hz)
  }
  if (frequency > 2000) {
    frequency = 2000; // Minimum frequency (0.5 Hz)
  }

  // Check time when toggling LED switch
  unsigned long currentMillis = millis(); // Get the current time
  if (currentMillis - previousMillis >= frequency) {
    // Save the last time the LED was toggled
    previousMillis = currentMillis;

    // Toggle the LED
    digitalWrite(ledPin, !digitalRead(ledPin));
  }
}