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/*
  Water cooler guard
 */
 
int flowSensorPin = 5;
int led1 = 12;
int led2 = 13;
int relayPin = 10;

int minTickCount = 10; // alarm if less ticks per 500 millisecs

int blinkState = 0;

 
void setup() 
{                
  pinMode(flowSensorPin, INPUT);
  pinMode(led1, OUTPUT);     
  pinMode(led2, OUTPUT);     
  pinMode(relayPin, OUTPUT);
  
  // start serial port at 9600 bps:
  Serial.begin(9600);
  Serial.println("Water cooler guard - INIT");
  digitalWrite(relayPin, LOW);
  
  // initial blinking
  digitalWrite(led1, HIGH);   
  digitalWrite(led2, LOW);   
  delay(200);
  digitalWrite(led1, LOW);   
  digitalWrite(led2, HIGH);   
  delay(200);
  digitalWrite(led1, HIGH);   
  digitalWrite(led2, LOW);   
  delay(200);
  digitalWrite(led1, LOW);   
  digitalWrite(led2, HIGH);   
  delay(200);
  digitalWrite(led1, LOW);   
  digitalWrite(led2, LOW);     
}

void loop() 
{  
  int ticks = getTickCount(500);
  
  Serial.print("Tick count: ");
  Serial.print(ticks);
  if (ticks >= minTickCount)
  {
    // all good, show green light
    digitalWrite(relayPin, HIGH);
    digitalWrite(led1, LOW);   
    digitalWrite(led2, HIGH);  
    blinkState = 0;    
  }
  else
  {
    // alert! red light
    Serial.print(" Low flow alert!");
    digitalWrite(relayPin, LOW);
    digitalWrite(led1, blinkState ? LOW : HIGH);   
    digitalWrite(led2, LOW);     
  
    blinkState = !blinkState;  
  }
  Serial.println();
}

// count the pulses from the flow sensor 
// for the given time in millisecs
int getTickCount(int milliSecs)
{
  unsigned long startTime = millis();
  unsigned long endTime = startTime+milliSecs;
  
  while (endTime < startTime)
  {
    // timer overrun (will probably never happen, but just in case)
    // simply wait a bit and retry
    delay(50);
    startTime = millis();
    endTime = startTime+milliSecs;
  }
  
  int count = 0;
  while (millis() < endTime)
  {
    // wait until low
    while(HIGH == digitalRead(flowSensorPin))
    {
      if (millis() >= endTime)
      {
        return count; // reached end time, jump out
      }
    }
    
    // count
    count++;
    
    // wait until high again
    while(LOW == digitalRead(flowSensorPin))
    {
      if (millis() >= endTime)
      {
        return count; // reached end time, jump out
      }
    }     
  }
  return count;
}