Do this on your own risk, although I experienced that wrong connections did'nt brick anything.
When you look at the UART header on the Matrix, the pins are, starting from left:
VCC, Tx, Rx, Gnd
I bought a RS232 to TTL convertor Ebay for less then 2 $
http://www.ebay.nl/itm/RS232-To-TTL-Con ... 2a24db90c8
You should connect VCC and GND to the corresponding pins on the convertor
connect the Tx on the matrix to the TX on the convertor
and the Rx on the matrix to the Rx on the convertor
Now you can plug the convertor in your PC serial port
I installed putty on my PC and made a serial connection in my case to COM2 with 115200 speed
Boot the matrix with the switch on "run" and see what happens.....
You can get into the U-boot prompt by hitting any key during the boot-up.
When you use a serial cable between your PC and the convertor, this might not work because the Rx in the cable I believe is connected to the Tx on the other side.
In this case you can swap the Rx en Tx connections so that Rx on the Matrix is connected to Tx on the convertor and Tx to Rx.
I found an old computer cable with the right connectors. This is a cable that connected the audio header on a PC motherboard with the CD-player. With some patience you can disassemble the conectors by carefully lifting the plastic tongues a bit (I use a stanly knife for that). Then you can pull out the metal part with the wire. Now you can put the wires in the right place. Best is to do this on the black connector while this is bigger end easyer to handle.
for photos visit http://hansiart.ddns.net/techniek/matri ... _port.html
Btw this website runs on an RK3188 device.
Good luck
