Why does "!=LOW" != "HIGH"?

Question

I'm learning about accessing ports directly on the ATMEGA 328 using an Arduino Uno. The program sets up pin 13 as an output and pin 2 as an input. I then enable the pull up resistor on pin 2.

I read Pin 2 and set the LED high or low depending on if pin 2 is high or low.

Why is it that I cannot seem to use == HIGH in my if statement instead of != LOW?

void setup() {
 MCUCR &= ~(1 << 4); //disables pull-up disable (redundant as default is off)
 DDRB |= (1 << 5); //sets pin 13 (B5 on ATMEGA 328) as output
 DDRD &= ~(1 << 2); //sets pin 2 (D2 on ATMEGA 328) as input (redundant as default is input)
 PORTD |= (1 << 2); //since it's an input sets pull-up resistor ON
 PORTB &= ~(1 << 5); //sets pin 13 (B5 on ATMEGA 328) as LOW
}
void loop() {
 if ((PIND & (1 << 2)) != LOW) PORTB |= (1 << 5); //sets pin 13 (B5 on ATMEGA 328) as HIGH
 else PORTB &= ~(1 << 5); //sets pin 13 (B5 on ATMEGA 328) as LOW
 delay(100);
}

Answer 1

Because

((PIND & (1 << 2)) != LOW)

means exactly

(PIND & 4) != 0

and that is true if PIND is 4, 5, 6, 7, 12, 13, ... (any number having 4 in it binary), so it yelds

4 != 0 

Which is definitively not equal

4 == 1

---

BTW: in C any integer != 0 is true and 0 is false, so you can as well write:

if (PIND & (1 << 2)) PORTB |= (1 << 5); //sets pin 13 (B5 on ATMEGA 328) as HIGH

Answer 2

if ((PIND & (1 << 2)) != LOW) PORTB |= (1 << 5); //sets pin 13 (B5 on ATMEGA 328) as HIGH
 else PORTB &= ~(1 << 5); //sets pin 13 (B5 on ATMEGA 328) as LOW

PIND & (1<<2) will return a value of either (1<<2) if PD.2 is high, or 0 if PD.2 is low.

So it basically says that if PD2 is high, set PB5; otherwise, clear PB5.enter code here

• Samee87: Thanks, Danny. Yeah I should have known... dork move on my part.