All the functions of the WiFi Module are managed by the powerful system on chip (SoC) ESP8266, that combines a 32 bit micro-controller (and many peripherals, such as GPIO, I2C, ADC, SPI, PWM) with a WiFi radio. 

The board’s I/O pins – 18 in all – are multi-talented. Every pin can be used as a digital input or output, for blinking LEDs or reading button presses. These pins are referenced in the Arduino IDE via an integer value between 0 and 21. (The A0-A3 pins can be referenced digitally using either their analog or digital pin number).

Nine pins feature analog to digital converters (ADCs) and can be used as analog inputs. These are useful for reading potentiometers or other analog devices using the analogRead([pin]) function.

There are five pins with pulse width modulation (PWM) functionality, which can be used as analog output using the analogWrite([pin], [value]) function. These pins are indicated on-board with a faint, white circle around them.

There are hardware UART (serial), I2C, and SPI pins available as well. These can be used to interface with digital devices like serial LCDs, XBees, IMUs, and other serial sensors.

The board has five external interrupts, which allow you to instantly trigger a function when a pin goes either high or low (or both). If you attach an interrupt to an interrupt-enabled pin, you’ll need to know the specific interrupt to pin map: pin 3 maps to interrupt 0, pin 2 is interrupt 1, pin 0 is interrupt 2, pin 1 is interrupt 3, and pin 7 is interrupt 4.

Since the main feature is its innate USB functionality, the most common way to power it is via USB. In this setup, the board will regulate to 3.3V the 5V supply coming in from the USB. The other end of the USB cable can be connected to either a computer, USB hub, or a USB wall adapter, which can (in most cases) provide more power.

Alternatively, if your board is living out in the wild, it can be powered through either the ‘RAW’ or ‘VCC’ pins. A supply going into the ‘RAW’ pin will be regulated down to the correct operating voltage (3.3V). To be safe, it shouldn’t be any higher than 9V, and it should be at least 1V more than the regulated voltage (e.g. > 4.3V).

If you power the board through the ‘VCC’ pin, keep in mind that this signal is unregulated. Only use this if you have a clean, regulated 3.3V supply to connect to it.

After power-up (or reset) the on-board WiFi module can boot in two different modes, depending on the logic levels applied on its pins GPIO0 and GPIO2. Since these pins are internally routed to the Arduino side (as reported in table 1), in your Arduino sketch you have to take care to correctly set these pins on reset (see the sketch example below).

IMPORTANT: before loading your sketch, please select the board “LilyPad Arduino USB” in the boards menu.
If you have accidentally selected another board, and already tried loading your sketch, read here: 

www.arduino.cc/en/Guide/ArduinoLilyPadUSB

This board (like Lilypad USB and Leonardo) use “Serial1” to communicate with on-board the WiFi module via TTL serial on pins 0 (RX) and 1 (TX).  “Serial” is reserved for USB CDC communication.

/**************************************************

 --- IMPORTANT ---: before to load your sketch, please select the board "LilyPad Arduino USB" in the boards menu.
 If you have accidentally select another board, and load your sketch, read here:
 www.arduino.cc/en/Guide/ArduinoLilyPadUSB

 Connection table:

 * ESP8266  Arduino
 * GPIO0    12
 * ENABLE   13
 * RX       TX
 * TX       RX
 * GND      GND

 About Serial
 The "Lilypad USB" (and the board derived from it) use "Serial1" to communicate via TTL serial on pins 0 (RX) and 1 (TX). 
 "Serial" is reserved for USB CDC communication.

 ***************************************************/

#define ESP_PROGRAM_PIN  12
#define ESP_ENABLE_PIN  13

void setup() {

  Serial1.begin(57600);        // Initialise serial 1 (WiFi Module)

  pinMode(ESP_ENABLE_PIN, OUTPUT);
  pinMode(ESP_PROGRAM_PIN, OUTPUT);

  // Set ESP module in RUN mode on reset 
  digitalWrite(ESP_PROGRAM_PIN, HIGH);  
  digitalWrite(ESP_ENABLE_PIN, HIGH);

  delay(5000);                 // Let's the module start

  // Discharge old partial messages
  Serial1.println("");

  // Enable real-time response
  Serial1.println("$PING 200");

  // Send Panel (Single Green LED, 150% size on new line with text Blinking)
  Serial1.println("$P:*15/L1G:0:Blinking;");

}

void loop() {

  delay(500);                // Wait 0.5 s
  Serial1.println("#L11");    // Turn ON LED 1
  delay(500);                // Wait 0.5 s
  Serial1.println("#L10");    // Turn OFF LED 1

}