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.
I found a seller of 1996-era CD-ROM
“Mitsumi” JST audio cables on eBay. They use the exact same plug as the UARTs on the Mele A1000G Quad. The pins are 3.3v POWER (do not wire up), TX, RX and GND.
I started by butchering the CD-ROM audio cable:
The shield is the black cable (RX). The white is TX. The red is GND.
I also butchered the CP2102 cable:
I hooked the respective cables together, put a small blob of solder on each joint (just to improve electrical connectivity, it’s probably not necessary), then wrapped each joint then the whole bundle it in several layers of electrical tape:
I finished off by drilling a small (¼”) hole in the top of the case for the cable:
(And it works too!)
For my reference mainly, attached below are the boot messages from the Mele A1000G Quad with the original Android kernel. Unfortunately the UART connector is just a little bit too small to take the CP2102 USB-serial adapter so now I have to find an Audio CD header block of the sort used by CD-ROMs in the 1990s. However I was able to connect the GND and TX which is enough to get the serial output below.
This site has been very useful.
I ordered it over 1 month ago, and it spent some time travelling around Sweden, but anyway it has now arrived. (To be fair, my colleague in the US ordered one and it arrived two days later).
This is a CP2102-based UART-USB connector which I ordered on Amazon for under £10 (inc tax and delivery). I’m hoping this will solve my serial port blues: