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examples/ExternalWakeup/ExternalWakeup.ino

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+/*
+  ExternalWakeup
+
+  This sketch demonstrates the usage of External Interrupts (on pins) to wakeup a chip in sleep mode.
+  Sleep modes allow a significant drop in the power usage of a board while it does nothing waiting for an event to happen. Battery powered application can take advantage of these modes to enhance battery life significantly.
+
+  In this sketch, shorting pin 8 to a GND will wake up the board.
+  Please note that, if the processor is sleeping, a new sketch can't be uploaded. To overcome this, manually reset the board (usually with a single or double tap to the RESET button)
+
+  This example code is in the public domain.
+*/
+
+#include "ArduinoLowPower.h"
+
+// Blink sequence number
+// Declare it volatile since it's incremented inside an interrupt
+volatile int repetitions = 1;
+
+// Pin used to trigger a wakeup
+const int pin = 8;
+
+void setup() {
+  pinMode(LED_BUILTIN, OUTPUT);
+  // Attach a wakeup interrupt on pin 8, calling repetitionsIncrease when the device is woken up
+  LowPower.attachInterruptWakeup(pin, repetitionsIncrease, CHANGE);
+}
+
+void loop() {
+  for (int i = 0; i < repetitions; i++) {
+    digitalWrite(LED_BUILTIN, HIGH);
+    delay(500);
+    digitalWrite(LED_BUILTIN, LOW);
+    delay(500);
+  }
+  // Triggers an infinite sleep (the device will be woken up only by the registered wakeup sources)
+  // The power consumption of the chip will drop consistently
+  LowPower.sleep();
+}
+
+void repetitionsIncrease() {
+  // This function will be called once on device wakeup
+  // You can do some little operations here (like changing variables which will be used in the loop)
+  // Remember to avoid calling delay() and long running functions since this functions executes in interrupt context
+  repetitions ++;
+}