The On-board Self-Test LED is connected to J6 pin 5.

In normal operation, the LED will illuminate when:

• The device is in the process of enumerating with the USB host controller during boot or plugin
• The device is receiving configuration data from the host
• A switch connected to this pin is closed.

In addition, you can use this LED for test purposes by defining J6 pin 5 as a LED. NOTE: The LED is connected between the pin and 5V power on the PCB. This means it will behave in an opposite way to other connected LEDs which are connected between the pins and Ground.

Connecting analog devices such as pots to this pin wil give strange results but you can use the LED for a basic pot test (brightness will vary).