// Install Pin change interrupt for a pin, can be called multiple times
 
void pciSetup(byte pin)
{
    *digitalPinToPCMSK(pin) |= bit (digitalPinToPCMSKbit(pin));  // enable pin
    PCIFR  |= bit (digitalPinToPCICRbit(pin)); // clear any outstanding interrupt
    PCICR  |= bit (digitalPinToPCICRbit(pin)); // enable interrupt for the group
}
 
volatile unsigned char tB;
volatile unsigned char oldB = 0;  // well, it doesn't.
 
ISR (PCINT0_vect) // handle pin change interrupt for port B
{ 
//*
  static unsigned long lastTime;
  unsigned long now = millis();
  if (now - lastTime < 50) return;
  lastTime = now;
//*/
  unsigned char newB = PINB; 

  tB = (oldB ^ newB); // & ~nB;
  oldB = newB; 
}

void setup() {  
  int i;
 
  Serial.begin(1152300);
  Serial.println("WTIF");

  pinMode(9, INPUT_PULLUP);
  pinMode(10, INPUT_PULLUP);
  pinMode(11, INPUT_PULLUP);

  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);

  digitalWrite(2, LOW);
  digitalWrite(3, LOW);
  digitalWrite(4, LOW);

  pciSetup(9);
  pciSetup(10);
  pciSetup(11);
  
  PORTB = 0xff;   // first time glitch?
}
 
int counter;

void loop() {
  unsigned char myTB;
  unsigned char theValue;

//  delay(50);

  cli();

  myTB = tB;
  theValue = myTB & oldB;
  tB = 0;  // wasn't safely 

  sei();

  if (myTB) {

    if (0) {
      Serial.print(counter); Serial.print("   "); counter++;
      Serial.print(tB, HEX); Serial.print("   ");
      Serial.print(theValue, HEX);
      Serial.println(" ");
    }

    switch (myTB) {
    case 2 :
      digitalWrite(2, !digitalRead(2));
      break;

    case 4 :
      digitalWrite(3, !digitalRead(3));
      break;

    case 8 : 
      digitalWrite(4, !digitalRead(4));
      break;

    }
  }
}