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WATCH-DOG_SLEEP_TEST/WATCH-DOG_SLEEP_TEST.ino

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+
+// Example of sleeping and saving power
+//
+// Author: Nick Gammon
+// Date:   25 May 2011
+
+#include <avr/sleep.h>
+#include <avr/wdt.h>
+
+#define LED 13
+
+// watchdog interrupt
+ISR(WDT_vect)
+  {
+  wdt_disable();  // disable watchdog
+  }
+
+void myWatchdogEnable(const byte interval)
+  { 
+  MCUSR = 0;                          // reset various flags
+  WDTCSR |= 0b00011000;               // see docs, set WDCE, WDE
+  WDTCSR =  0b01000000 | interval;    // set WDIE, and appropriate delay
+
+  wdt_reset();
+  set_sleep_mode (SLEEP_MODE_PWR_DOWN); 
+  sleep_mode();            // now goes to Sleep and waits for the interrupt
+  }
+
+void setup()
+{
+pinMode (LED, OUTPUT);
+}  // end of setup
+
+void loop()
+{
+  digitalWrite (LED, HIGH);  // awake
+  delay (2000);    // ie. do stuff here
+  digitalWrite (LED, LOW);  // asleep
+
+  // sleep for a total of 20 seconds
+  for (int i = 0; i<5; i++) {
+    myWatchdogEnable (0b100001);  // 8 seconds
+  }
+    
+ 
+}  // end ofloop
+
+// sleep bit patterns:
+//  1 second:  0b000110
+//  2 seconds: 0b000111
+//  4 seconds: 0b100000
+//  8 seconds: 0b100001
+
+