This is the explanation how to test the Xmega128a4u breakout board in mass production process.

All pins on the two 20-pin connectors are tested against short circuit or open connection.
The crystal is testet by starting the crystal oscillator.
LEDs are optically tested.
USB connector is testet against short circuit and open connection.
USB ESD protection is testet: BAS70 diode forward voltage, Z-diode breakdown voltage
Reference voltage capacitors are tested.

Testboard

All the functions are tested by the passive testboard. "Passive" means there is no processor on the board. The testprocess is done by the Xmega Breakout Board.

Usage

Connect a 15 V to 30 V DC powersupply to the connector CON1. On normal operation it uses on maximum 100 mA.
Connect the programmer to the PDI-interface P1 on the testboard.
Connect an USB-cable to the USB-port J1 on the testboard.
Plug the Xmega Breakout Board in the IC1 socket. (micro-USB-connector on the left side)
Connect the micro-USB-cable to the Xmega Breakout Board.
Download testsoftware to the controller.
Check the LEDs.
Unplug USB-cable and Xmega Breakout Board.

Indicators

PWR-LED (D1) on the testboard must be on. Powersupply to the testboard is OK, testboard is OK, no short circuit.

With Xmega Breakout Board pluged in and testsoftware on the controller:

After plugging in the USB-cable: µUSB PWR OK (D12) should light up (blinking)