Enable Watchdog Timer

[amcjen]

Prevents weird hung states when unplugging Scouts after configuration.

http://forum.arduino.cc/index.php?topic=63651.0

c++
/* 
Watchdog Timer Basic Example
10 June 2011
Nicolas Larsen
*/
#include <avr/wdt.h>
int loop_count = 0;
void setup()
{
 Serial.begin(9600);
 Serial.println("Starting up...");
 pinMode(13,OUTPUT);
 digitalWrite(13,HIGH);
 delay (500);
 watchdogSetup();
}
void watchdogSetup(void)
{
cli(); # # // disable all interrupts
wdt_reset(); // reset the WDT timer
/*
 WDTCSR configuration:
 WDIE = 1: Interrupt Enable
 WDE = 1 :Reset Enable
 WDP3 = 0 :For 2000ms Time-out
 WDP2 = 1 :For 2000ms Time-out
 WDP1 = 1 :For 2000ms Time-out
 WDP0 = 1 :For 2000ms Time-out
*/
// Enter Watchdog Configuration mode:
WDTCSR |= (1<<WDCE) | (1<<WDE); 
// Set Watchdog settings:
 WDTCSR = (1<<WDIE) | (1<<WDE) | (0<<WDP3) | (1<<WDP2) | (1<<WDP1) | (1<<WDP0);
sei();
}
void loop()
{
for (int i = 0; i <= loop_count;i++){
 digitalWrite(13,HIGH);
 delay(100);
 digitalWrite(13,LOW);
 delay(100);
 }
 loop_count++;
 wdt_reset();
 Serial.print(loop_count);
 Serial.print(". Watchdog fed in approx. ");
 Serial.print(loop_count*200);
 Serial.println(" milliseconds.");
}
ISR(WDT_vect) // Watchdog timer interrupt.
{
// Include your code here - be careful not to use functions they may cause the interrupt to hang and 
// prevent a reset. 
}