Spikee

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

volatile byte rpmcount;
volatile int status;

unsigned int rpm;

unsigned long timeold;

 void rpm_fun()
 {
   //Each rotation, this interrupt function is run twice, so take that into consideration for
   //calculating RPM
   //Update count
      rpmcount++;


 }

void setup()
 {
 lcd.begin(20, 4);
   //Interrupt 0 is digital pin 2
   //Triggers on FALLING (change from HIGH to LOW)
   attachInterrupt(2, rpm_fun, FALLING);






   rpmcount = 0;
   rpm = 0;
   timeold = 0;
   status = LOW;
 }

 void loop()
 {
   //Update RPM every second
   delay(1000);
   lcd.clear();
lcd.setCursor(0,0);
lcd.print("     RPM: ");
   //Don't process interrupts during calculations
   detachInterrupt(2);
   //Note that this would be 60*1000/(millis() - timeold)*rpmcount if the interrupt
   //happened once per revolution instead of twice. Other multiples could be used
   //for multi-bladed propellers or fans
   rpm = 30*1000/(millis() - timeold)*rpmcount;
   timeold = millis();
   rpmcount = 0;

   lcd.setCursor(14,0);
lcd.print(rpm);



   //Restart the interrupt processing
   attachInterrupt(2, rpm_fun, FALLING);

  }