#include <LiquidCrystal.h>

TCCR2B = TCCR2B & 0b11111000 | 0b00000010;

unsigned int rpm = 0;
unsigned int pwm = 255;
unsigned int set = 0;
unsigned long present = 0;
unsigned long past = 0;
unsigned long past2 = 0;
unsigned long past3 = 0;
unsigned long past4 = 0;
float time = 0;
float itd = 0;

LiquidCrystal lcd(4, 5, 6, 7, 8, 9);

void setup() {

pinMode(2, INPUT_PULLUP);

attachInterrupt(digitalPinToInterrupt(2), sensing, FALLING);

pinMode(3, OUTPUT);
analogWrite(3, 255);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);

lcd.begin(16, 2);

}

void sensing() {
  time = present - past;
  past = present;
}

void loop() {
  present = micros();

itd = 1000000 / time;
rpm = itd * 60;

if(rpm < set && present - past3 >= 750 && pwm >= 1) {
  pwm = pwm - 1;
  past3 = present;
}

if(pwm >= 255) {
  pwm = 255;
}

if(pwm <= 0) {
  pwm = 0;
}

if(rpm > set && present - past4 >= 750 && pwm <= 254) {
  pwm = pwm + 1;
  past4 = present;
}

set = analogRead(A0) * 5.5;

if(present - past2 >= 500000) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(rpm);
  lcd.setCursor(6, 0);
  lcd.print(pwm);
  lcd.setCursor(0, 1);
  lcd.print(set);
  time = 200000000;
  past2 = present;
}
analogWrite(3, pwm);
}