A test to do see if we can modify the volatile variable in the middle of a switch

loopbackinterupt.ino

volatile uint8_t position = 0;
uint8_t test = 0;
const byte outpin = 3;      //Wire from 2 to 3
const byte interruptPin = 2;

void setup() {
  pinMode(outpin, OUTPUT);
  pinMode(interruptPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(interruptPin), blink, CHANGE);

  Serial.begin(9600);
  while (!Serial) {
    ;  // wait for serial port to connect. Needed for native USB port only
  }
}

void blink() {
  position = position+1;
}


void loop() {
  position = 1;
  test = 0;

  switch (position) {
    case 1:
      test = test + 1;
      digitalWrite(outpin, HIGH);
      digitalWrite(outpin, LOW);
      break;
    case 2:
      test = test + 2;
      position = 9;
      break;
    case 9:
      test = test + 4;
      position = 10;
      break;
    case 10:
      test = test + 8;
      break;   
    case 20:
      test = test + 8;
      break;   
    case 30:
      test = test + 8;
      break;   
    case 50:
      test = test + 8;
      break;   
    case 128:
      test = test + 8;
      break;   
    default:
      test = 99;
  }
  Serial.println(test);
  Serial.println("Done");
}