Project18.Button
===================

Description
------------
This is a basic button module. You can simply plug it into an IO shield to have 
your first try of Arduino.

Specification
--------------
- Supply Voltage: 3.3V to 5V
- Interface: Digital
- Dimensions: 30*20mm
- Weight: 4g

Connect
--------
.. image:: /img/connect/18_bb.png

Code
-----
.. code-block:: c

    int led = 13; //Define the LED pin
    int buttonpin = 3; //Define the push button pin  
    int val; //Define a numeric variable
    int ledState = LOW; //LED status variable, the initial value is off

    void setup() {
    pinMode(led,OUTPUT);
    pinMode(buttonpin,INPUT);
    digitalWrite(led, ledState); //Set the initial LED state according to ledState
    }

    void loop() {
    val = digitalRead(buttonpin); // Read button status
    if(val==LOW) // If the button is pressed
    {
        ledState = HIGH; // Set ledState to HIGH(on)
    }
    else
    {
        ledState = LOW; // Set ledState to LOW
    }
    digitalWrite(led, ledState); 
    }

Phenomenon
-----------
.. image:: /img/phenomenon/18.jpg