First of all, I would like to thank KSK Electrics for kindly donating this S400 stick (and a MK908) to support the Linux kernel porting on RK3188 devices.
A serial console for the Cozyswan S400 was needed in order to debug the boot problems encountered with the RK3188 kernel source "freed" by Andy from Rikomagic.
Also, since this kernel removed support for the framebuffer console (the text you [should] see on screen at boot, or in text Linux, before installing any XFCE/Gnome/...), the serial console is the only way to see what's happening when there is something wrong.
Fortunately I was able to successfully backport the framebuffer console so that now text is back on screen for Linux!
In any case here is the mod to get the serial console pins, thanks to Alok Sinha, who found those pads to be the serial output. They looked to me so much like an IR tx/rx connector that I would have tested every other pad before trying those! :)
|Left to Right: The R (RX) pad for receiving keystrokes, the T (TX) pad for sending to your|
Serial2USB module the text, and the required G (Ground)
Actually only TX and Gnd are needed to receive the boot text, so I usually solder just those two.
|The pads are small, with a tiny bit of solder on the iron tip and|
another tiny bit on the cable, you should get good results