user31946: I changed my arduino NodeMCU application pin mode to use INPUT_PULLUP mode instead of INPUT. D8 input pin is not working as expected, I is always in LOW even the button is pressed or not. 
I have 3 input pins (D2, D7, D8), when I changed to internal pull up resistor, I removed each external resistors from input and changed the circuit accourding to this: https://www.arduino.cc/en/Tutorial/InputPullupSerial
D2 and D7 works well, but D8 is not. I checked with a volage between GND and pins:

when button on D2, D7 is not pressed: 2.95 - 3 V  
when button on D8 is not pressed: 0.8 V
when button on D2, D7, D8 is pressed: 0V (as expected)

You can see my code in github:
https://github.com/kisdaniel/HomeDashboardGarageDoorOpener

user37622: Pin D8 is esp8266 pin 15. This pin is one of the boot configuration pins and for use on a dev board, it must be pulled down at boot. So the NodeMcu has a pull down circuit on this pin and internal pullup is weaker then this external pulldown.

31946: <p>I changed my arduino NodeMCU application pin mode to use INPUT_PULLUP mode instead of INPUT. D8 input pin is not working as expected, I is always in LOW even the button is pressed or not. </p>

<p>I have 3 input pins (D2, D7, D8), when I changed to internal pull up resistor, I removed each external resistors from input and changed the circuit accourding to this: <a href="https://www.arduino.cc/en/Tutorial/InputPullupSerial" rel="nofollow noreferrer">https://www.arduino.cc/en/Tutorial/InputPullupSerial</a></p>

<p>D2 and D7 works well, but D8 is not. I checked with a volage between GND and pins:</p>

<ul>
<li>when button on D2, D7 is not pressed: 2.95 - 3 V  </li>
<li>when button on D8 is not pressed: 0.8 V</li>
<li>when button on D2, D7, D8 is pressed: 0V (as expected)</li>
</ul>

<p>You can see my code in github:
<a href="https://github.com/kisdaniel/HomeDashboardGarageDoorOpener/tree/4cb86ffa2fbca5346bb1bd11c512f242a2a73cfc" rel="nofollow noreferrer">https://github.com/kisdaniel/HomeDashboardGarageDoorOpener</a></p>
 37622: <p>Pin D8 is esp8266 pin 15. This pin is one of the <a href="https://github.com/espressif/esptool/wiki/ESP8266-Boot-Mode-Selection#required-pins" rel="noreferrer">boot configuration pins</a> and for use on a dev board, it must be pulled down at boot. So the NodeMcu has a pull down circuit on this pin and internal pullup is weaker then this external pulldown.</p>
