[solved] ATTiny85 if statement failing mysteriously

Other Hardware 3rd Party Boards
8

Ok, Thanks to DrAzzy for your help on this. Everything is working fine now and here is the final code that made it all possible. I removed the interrupt enable/disable calls all together and just went with a while loop to give me a 1 sec sample. Of course this means that the interrupt is going to be firing about 8000 times a sec (approx speed of the fan) but it shouldn't be a problem (unless someone does see a problem with that).

const int ledGrn = 0;
const int pwmPin = 1;
const int potPin = A2;
int inVal = 0;
volatile unsigned long NbTopsFan;
int Calc;
int hallsensor = 2;

unsigned long interval = 5000;
unsigned long curTime;
volatile bool cooling = true;

void setup() {
  pinMode(ledGrn, OUTPUT);
  pinMode(pwmPin, OUTPUT);
  analogWrite(pwmPin, 0);
  pinMode(potPin, INPUT);
  pinMode(hallsensor, INPUT);
  attachInterrupt(0, rpm, RISING);
  digitalWrite(ledGrn, HIGH);
  delay(10);
}

void loop() {
  if (cooling) {
    inVal = analogRead(potPin);
    analogWrite(pwmPin, inVal / 4);
    if (millis() >= interval) {
      interval = (millis() + 6000UL);
      checkFan();
    }
  } else {
    analogWrite(pwmPin, 0);
    digitalWrite(ledGrn, LOW);
    delay(500);
    digitalWrite(ledGrn, HIGH);
    delay(150);
    digitalWrite(ledGrn, LOW);
    delay(150);
    digitalWrite(ledGrn, HIGH);
    delay(150);
    digitalWrite(ledGrn, LOW);
    checkFan();
  }
}

void rpm() {
  NbTopsFan++;
}

void checkFan() {
  NbTopsFan = 0;
  unsigned long rpmNum = 0;
  unsigned long pause = millis() + 1000UL;
  while (millis() <= pause) {
    rpmNum = NbTopsFan;
  }
  Calc = ((rpmNum * 60) / 2);
  if (Calc >= 6500) {
    cooling = true;
    digitalWrite(ledGrn, HIGH);
  } else {
    cooling = false;
    digitalWrite(ledGrn, LOW);
  }
}