Init commit with many years of arduino sketches and projects. I dont know if the esp8266 includes much, but there are also libraries. I hope they dont have crazy automatic versioning through the Arduino IDE.

Projects/libraries/Installed_libs/NewPing/examples/TimerExample/TimerExample.pde

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+// ---------------------------------------------------------------------------
+// While the NewPing library's primary goal is to interface with ultrasonic sensors, interfacing with
+// the Timer2 interrupt was a result of creating an interrupt-based ping method. Since these Timer2
+// interrupt methods were built, the library may as well provide the functionality to use these methods
+// in your sketches.  This shows how simple it is (no ultrasonic sensor required).  Keep in mind that
+// these methods use Timer2, as does NewPing's ping_timer method for using ultrasonic sensors.  You
+// can't use ping_timer at the same time you're using timer_ms or timer_us as all use the same timer.
+// ---------------------------------------------------------------------------
+
+#include <NewPing.h>
+
+#define LED_PIN 13 // Pin with LED attached.
+
+void setup() {
+  pinMode(LED_PIN, OUTPUT);
+  NewPing::timer_ms(500, toggleLED); // Create a Timer2 interrupt that calls toggleLED in your sketch once every 500 milliseconds.
+}
+
+void loop() {
+  // Do anything here, the Timer2 interrupt will take care of the flashing LED without your intervention.
+}
+
+void toggleLED() {
+  digitalWrite(LED_PIN, !digitalRead(LED_PIN)); // Toggle the LED.
+}