Experiment 3: The Null program tests communication to the board. There are two white LEDs labelled TX and RX, TX for transmit and RX for receive. These two LEDs flicker when the computer is downloading or uploading programs to the Arduino board. On the IDE screen where the Null program was written, there is an button below the Edit menu with a arrow pointing right. When the cursor moves over this button, text appears identifying this as the upload button. A mouse click with the cursor over this upload button will send the program through the USB cable to the Arduino board. Observe the RX and TX light while the null program is uploaded to the board. The flicker of the TX RX LEDs means the board is ready for programing.