The PmodBT2 is a powerful peripheral module employing the Roving Networks® RN-42 to create a fully integrated Bluetooth interface.
The PmodBT2 uses a standard 12-pin connection and communicates via UART. There is a secondary SPI header on the board for updating the RN-42 firmware if needed.
There are two UART signal pin assignment conventions in use on Digilent products. This product uses the new signal assignment convention. Connecting a product using the new convention with one using the old convention requires the use of a UART Crossover Cable (not included).
for a more detailed explanation.