Getting stuck in Timer1 interrupt loop

Projects Programming
5

I believe that & and && is identical for two bool operands,
nevertheless it is better to use the boolean && if that is the intention.

& as well as && have a lower precedence than comparison operators,
so it does not change the meaning of the expression.

https://en.cppreference.com/w/cpp/language/operator_precedence

const uint8_t val1_targetValue = 1;
const uint8_t val2_targetValue = 2;

void setup() {
  Serial.begin(115200);
  for (uint8_t i = 1; i < 3; i++) {
    for (uint8_t j = 1; j < 3; j++) {
      if (checkFor(i, j)) {
        Serial.println(F("different result"));
      } else {
        Serial.println(F("same result"));
      }
    }
  }
}

bool checkFor(uint8_t v1, uint8_t v2) {
  bool var1 = (v1 == val1_targetValue && v2 == val2_targetValue);
  bool var2 = (v1 == val1_targetValue & v2 == val2_targetValue);
  Serial.print(v1);
  Serial.print(F(" == "));
  Serial.print(val1_targetValue);
  Serial.print(F(" && "));
  Serial.print(v2);
  Serial.print(F(" == "));
  Serial.print(val2_targetValue);
  Serial.print(F(" gives "));
  Serial.println(var1 ? "true" : "false");
  Serial.print(v1);
  Serial.print(F(" == "));
  Serial.print(val1_targetValue);
  Serial.print(F(" &  "));
  Serial.print(v2);
  Serial.print(F(" == "));
  Serial.print(val2_targetValue);
  Serial.print(F(" gives "));
  Serial.println(var2 ? "true" : "false");
  return var1 != var2;
}

void loop() {}

1 == 1 && 1 == 2 gives false
1 == 1 &  1 == 2 gives false
same result
1 == 1 && 2 == 2 gives true
1 == 1 &  2 == 2 gives true
same result
2 == 1 && 1 == 2 gives false
2 == 1 &  1 == 2 gives false
same result
2 == 1 && 2 == 2 gives false
2 == 1 &  2 == 2 gives false
same result

The usage of & like this will trigger a warning:

Somewhere\oneortwoampersands.ino:19:19: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
   bool var2 = (v1 == val1_targetValue & v2 == val2_targetValue);
                ~~~^~~~~~~~~~~~~~~~~~~