Do I understand that i needs to cut T_jump JT1 and JT2 and connect other chip into J13 (contact 3 and 4/UART_RX_C, UART_TX_C)?
In the documentation on
http://8devices.com/media/files/Carambola2.pdf described - J12, J13 - 2 x 10 2.54 mm pitch prototyping area holes, but really J12,J13 - 2 x 20 2.4 mm.