#include <LiquidCrystal_I2C.h>

// Instantiate the Objects
LiquidCrystal_I2C lcd(0x27, 16, 2);  // 3F the address of the LCD

#define rpmInput 2

int switchPin = 11; // choose the input pin (for a pushbutton)

int rpm = 0;
//int pid;
unsigned long millisBefore;
volatile int objects;

void setup(){

  Serial.begin(57600);
  Serial.println("Welcome to the Serial Monitor!");
  Serial.println("---------------------------------");

  attachInterrupt(digitalPinToInterrupt(rpmInput), count, FALLING);
  delay(1000);

  pinMode(switchPin, INPUT); // declare as input

  // Initialize the display
  lcd.init();
  lcd.init();
  lcd.backlight();
  lcd.noCursor();

  pinMode(rpmInput, INPUT);
}//end setup


void loop() {
  analogWrite(11,110);

  if (millis() - millisBefore > 1000) {
    rpm = (objects / 3.0)*60;
    objects = 0;
    millisBefore = millis();
  }
  delay(100);

  lcd.setCursor(4, 0);
  lcd.print("RPM: ");
  lcd.setCursor(9, 0);
  lcd.print(rpm);
}

void count() {
  objects++;
}