The Arduino UNO board layout.

The Arduino UNO board layout

LEDs on Arduino UNO board

• The Power LED indicates that the board has power. 
• The TX and RX LEDs indicate serial communications traffic. 
• TX is blinking when transmitting, and RX is blinking when receiving. 
• The Pin 13 LED is connected to the Arduino Digital I/O pin 13 and can be used for a variety of software tests without having to add any external hardware to see the software in action.

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Arduino Uno Rev3-------->

How an Arduino Program Works---------->

Arduino Uno Pinout diagram----------->

• What is Arduino?
• Why Arduino?
• How do I use Arduino?