const int pwmPin = 9;        // PWM pin to control motor speed
int currentSpeed = 0;        // Initial motor speed (0 - 255)
int targetSpeed = 0;         // Target motor speed (0 - 255)
int stepSize = 5;            // Increment value for smooth transitions (adjust this value as needed)
unsigned long previousMillis = 0;  // To track time for smooth transitions
const long interval = 20;    // Interval time for speed updates (in milliseconds)

void setup() {
  pinMode(pwmPin, OUTPUT);
  Serial.begin(9600);  // Start Serial communication at 9600 baud rate
  Serial.println("Motor Speed Control - Use keys: '1' to '5' to change speed");
}

void loop() {
  // Check if there's any data from the serial monitor
  if (Serial.available() > 0) {
    char key = Serial.read();  // Read the incoming byte

    // Map keypresses to target speeds
    if (key == '1') {
      targetSpeed = 14;  // Low speed
    }
    else if (key == '2') {
      targetSpeed = 102; // Medium low speed
    }
    else if (key == '3') {
      targetSpeed = 153; // Medium speed
    }
    else if (key == '4') {
      targetSpeed = 204; // Medium high speed
    }
    else if (key == '5') {
      targetSpeed = 255; // Full speed
    }
    else if (key == '0') {
      targetSpeed = 0;   // Stop motor
    }

    // Print the selected target speed to the Serial Monitor for feedback
    Serial.print("Target Speed: ");
    Serial.println(targetSpeed);
  }

  // Gradually adjust the motor speed to the target speed for smooth transitions
  unsigned long currentMillis = millis();

  // Only update the speed if enough time has passed
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    // Gradually increase or decrease the speed to reach the target
    if (currentSpeed < targetSpeed) {
      currentSpeed += stepSize;  // Increase speed
      if (currentSpeed > targetSpeed) {
        currentSpeed = targetSpeed;  // Don't overshoot the target
      }
    }
    else if (currentSpeed > targetSpeed) {
      currentSpeed -= stepSize;  // Decrease speed
      if (currentSpeed < targetSpeed) {
        currentSpeed = targetSpeed;  // Don't overshoot the target
      }
    }

    // Set the new motor speed (PWM signal)
    analogWrite(pwmPin, currentSpeed);
  }
}