As I’ve said before, developer boards should come with all the bits, and a UART is essential for development on ARM.
I built my own using the jump leads from an unused CP2102, and this 1.8v FTDI serial to USB cable purchased previously.
The ODROID-XU board has a four pin Molex-type UART connector. The pin-out is: 1 = Power (do not connect), 2 = RX, 3 = TX, 4 = Ground. Pin 1 has the triangular notch on the outside of the connector. In the photo above, black is connected to pin 4 (ground), blue is connected to pin 3 (TX), and purple is connected to pin 2 (RX).
The FTDI cable has: Black = ground, Yellow = RX, Orange = TX.
Normally I would swap RX & TX in the cable, but that didn’t work here, so as you can see I’ve connected RX-RX, TX-TX straight through.
The photograph shows the connection before I wrapped the whole lot in many layers of black electrical tape.