DUE External Interrupt problems

Official Hardware Mega Due
1

I'm trying a simple sketch to test interrupts on my DUE. For some reason, when I upload the following sketch, my IDE (Arduino 1.6.8) no longer recognizes the board that is attached. It also doesn't run the main loop. The upload completes successfully and then the board detaches and doesn't run any of the logic it supposedly "uploaded". Any help is appreciated!

#define BTN_MENU_PWR     43
#define LCD_BACKLIGHT    49

void wakeUpNow() {

   digitalWrite(LCD_BACKLIGHT, 0);
   delay(10000);
   SerialUSB.println("Interrupt working!");

}

void setup() {

 SerialUSB.begin(9600);
 pinMode(BTN_MENU_PWR, INPUT_PULLUP);
 attachInterrupt(BTN_MENU_PWR, wakeUpNow, LOW);
 SerialUSB.println("Interrupt attached.");
 
}

void loop() {

 analogWrite(LCD_BACKLIGHT, 255);
 delay(2000);
 analogWrite(LCD_BACKLIGHT, 0);
 delay(2000);

}

Moderator edit:
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tags added.

2 
void wakeUpNow() {

    digitalWrite(LCD_BACKLIGHT, 0);
    delay(10000);
    SerialUSB.println("Interrupt working!");

}

delay() does NOT work in an ISR. Is there some part of "An ISR must be fast" that doesn't apply to you? Here's a hint. No, there isn't.

3

Didn't realize that. Works now. Thanks Paul!