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/toneAC/examples/toneAC_dual_LED/toneAC_dual_LED.pde

@@ -0,0 +1,25 @@
+// ---------------------------------------------------------------------------
+// Connect a two-pin dual LED to the following pins with inline 220 ohm resistor.
+//   Pins  9 & 10 - ATmega328, ATmega128, ATmega640, ATmega8, Uno, Leonardo, etc.
+//   Pins 11 & 12 - ATmega2560/2561, ATmega1280/1281, Mega
+//   Pins 12 & 13 - ATmega1284P, ATmega644
+//   Pins 14 & 15 - Teensy 2.0
+//   Pins 25 & 26 - Teensy++ 2.0
+// Connect the center lead of a potentiometer to analog pin A0 and the other two leads to +5V and ground.
+// ---------------------------------------------------------------------------
+
+#include <toneAC.h>
+
+unsigned long timestamp = 0; // Stores when the next time the routine is set to run.
+
+void setup() {}
+
+void loop() {
+  if (millis() > timestamp) { // Is it time yet?
+    timestamp += 500;         // Set the next time routine will run. 500 ms because the lowest frequency is 2 Hz, which is a half second.
+    int pot = analogRead(A0);            // Read the potentiometer connected to analog pin A0 to control alternating flashing speed.
+    int freq = map(pot, 0, 1023, 2, 40); // Convert pot analog values to a range from 2 to 40 Hz.
+    toneAC(freq, 10, 0, true);           // Set the frequency and have it run forever in the background (next event should take over in 500 ms).
+  }
+  /* Do a bunch of other stuff here, it won't affect toneAC doing its thing. */
+}