Problem using WHILE in void loop()

Using Arduino Programming Questions
1

I am trying to use a while statement in void loop() to wait for a state change in a GPIO input. However, even though it compiles without error, I get stack overflows when it runs on my ESP8266 board, as seen in the serial monitor window. The device starts, gives the error message then reboots itself. I am posting the simple code and the error message:

const int DOOR_SENSOR_PIN = 4; // Arduino pin connected to door sensor's pin

int doorState;

void setup() {
Serial.begin(115200); // initialize serial
pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode
}

void loop() {
doorState = digitalRead(DOOR_SENSOR_PIN); // read state
while (digitalRead(DOOR_SENSOR_PIN)) { }

if (doorState == HIGH) {
Serial.println("The door is open");
} else {
Serial.println("The door is closed");
}
}

And here is the output I get:

Soft WDT reset

ctx: cont
sp: 3ffffda0 end: 3fffffd0 offset: 01b0

stack>>>
3fffff50: 40202400 3ffefa14 3ffef9e4 4020235e
3fffff60: 0001c200 0000001c 00000003 3ffef9fc
3fffff70: feefeffe feefeffe 3ffee85c 3ffee898
3fffff80: 3fffdad0 00000001 3ffee85c 402028f8
3fffff90: 0001c200 0000001c 00000000 feefeffe
3fffffa0: feefeffe 00000000 3ffee890 4020270b
3fffffb0: feefeffe feefeffe 3ffee890 40202c7c
3fffffc0: feefeffe feefeffe 3ffe85d8 401000e5
<<<stack<<<

ets Jan 8 2013,rst cause:2, boot mode:(1,7)

ets Jan 8 2013,rst cause:4, boot mode:(1,7)

wdt reset

Can someone help this newbie with this? Thanks!

2

It appears that your ESP device has a watchdog timer waiting for a crash. I'll guess that something 'pats' the dog for you but your while loop prevents it from running so the watchdog thinks that your code has hung.

You will need to restructure your code to avoid a while.

3

Use if, not while.

If (whatever you are waiting for) {
  // Do stuff;
}

There's a tutorial Demonstration code for doing several things at the same time, you need read it and incorporate what you learn into your code.