#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);


// which pin to use for reading the sensor? can use any pin!
#define FLOWSENSORPIN 2

// count how many pulses!
volatile uint16_t pulses = 0;
// track the state of the pulse pin
volatile uint8_t lastflowpinstate;
// you can try to keep time of how long it is between pulses
volatile uint32_t lastflowratetimer = 0;
// and use that to calculate a flow rate
volatile float flowrate;
// Interrupt is called once a millisecond, looks for any pulses from the sensor!
SIGNAL(TIMER0_COMPA_vect) {
 uint8_t x = digitalRead(FLOWSENSORPIN);

 if (x == lastflowpinstate) {
   lastflowratetimer++;
   return; // nothing changed!
 }

 if (x == HIGH) {
   //low to high transition!
   pulses++;
 }
 lastflowpinstate = x;
 flowrate = 1000.0;
 flowrate /= lastflowratetimer; // in hertz
 lastflowratetimer = 0;
}

void useInterrupt(boolean v) {
 if (v) {
   // Timer0 is already used for millis() - we'll just interrupt somewhere
   // in the middle and call the "Compare A" function above
   OCR0A = 0xAF;
   TIMSK0 |= _BV(OCIE0A);
 } else {
   // do not call the interrupt function COMPA anymore
   TIMSK0 &= ~_BV(OCIE0A);
 }
}

void setup() {
  Serial.begin(9600);
  Serial.print("Flow sensor test!");
  lcd.begin(20, 4);

  pinMode(FLOWSENSORPIN, INPUT);
  digitalWrite(FLOWSENSORPIN, HIGH);
  lastflowpinstate = digitalRead(FLOWSENSORPIN);
  useInterrupt(true);
}

void loop() // run over and over again
{
 lcd.setCursor(0, 0);
 lcd.print("Pulses:"); lcd.print(pulses, DEC);
 lcd.print(" Hz:");
 lcd.print(flowrate);
 //lcd.print(flowrate);
 Serial.print("Freq: "); Serial.println(flowrate);
 Serial.print("Pulses: "); Serial.println(pulses, DEC);



 // if a plastic sensor use the following calculation
 // Sensor Frequency (Hz) = 7.5 * Q (Liters/min)
 // Liters = Q * time elapsed (seconds) / 60 (seconds/minute)
 // Liters = (Frequency (Pulses/second) / 7.5) * time elapsed (seconds) / 60
 // Liters = Pulses / (7.5 * 60)
 float liters = pulses;
 liters /= 7.5;
 liters /= 60.0;

// _________________________     AB HIER:    _________________________________

 float z;

 z = flowrate * 60 / 400; // hier kommt 5-6 liter/min raus, müssten aber ca. 2,67 l/min sein

 lcd.setCursor(0,2);
 lcd.print(z,2);
 delay(300); //damit das LCD Zeit hat, die Werte auch anzuzeigen


/*
// if a brass sensor use the following calculation
float liters = pulses;
liters /= 8.1;
liters -= 6;
liters /= 60.0;
*/
 Serial.print(liters); Serial.println(" Liters");
 lcd.setCursor(0, 1);
 lcd.print(liters); lcd.print(" Liters ");

 delay(100);
}