const int inputPin = 15;  // Define the pin for the input signal
volatile unsigned long pulseCount = 0;  // Variable to store pulse count
unsigned long startTime;  // Variable to store the start time
unsigned long frequency = 0;  // Variable to store the frequency

void IRAM_ATTR countPulse() {
    pulseCount++;  // Increment pulse count each time an interrupt occurs
}

void setup() {
    Serial.begin(115200);
    pinMode(inputPin, INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(inputPin), countPulse, RISING);  // Count rising edges
    startTime = millis();  // Initialize start time
}

void loop() {
    unsigned long currentTime = millis();
    
    // Update every second (1000 milliseconds)
    if (currentTime - startTime >= 1000) {
        // Calculate frequency
        frequency = pulseCount;
        pulseCount = 0;  // Reset pulse count
        startTime = currentTime;  // Reset start time
        
        // Print frequency to Serial Monitor
        Serial.print("Frequency: ");
        Serial.print(frequency);
        Serial.println(" Hz");
    }
}