Friday, July 12, 2013

Serial console mod for RK3188 stick Cozyswan S400

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

Omegamoon, who did the MK808 (RK3066) and MK908 (RK3188) sticks' serial console mods, recommends this nice Serial2USB module.

The three clams, as I call them

You can find here the Serial mod instructions for the Measy U2C RK3066 stick.

I hope it helps!


  1. Great work, like allways galland ;)

  2. Awesome, great stuff! I'm reading your blog (and also omegamoon's blog) to the letter, it's just great to see people working on getting Linux to run on these kind of devices. These TV sticks are cheap, easy to get by and also quite hackable with the help of your much valued work. Keep it coming!

  3. What is the wifi chip in Cozyswan s400?

    1. Android boot log talks about "Realtek 8188EU USB WiFi driver (Powered by Rockchip,Ver 3.10.WFD) init." and some lines later you see this message prefix "RTL871X: ..."
      However I wasn't able to activate it using the 8188EU driver in the kernel source (though the Wifi+BT chips always beat me)

    2. If you insmod 8188eu module from Android, does the wifi work in linux?

  4. Welcome

    I know it's not the subject but I have no one to ask.
    Rockchip RK3066 have:
    Peripheral I / F: I2C 5x, 4x UART, SPI 2x and 4x PWM.

    I'm interested in access to the I2C bus. Do you know how to access it from the Android or Linux (Picuntu)?

    Other distributions SOC (AM335x ARM ® 1GHz Cortex-A8, Broadcom BCM2835) enough to install packages:

    sudo apt-get install python-smbus
    sudo apt-get install i2c-tools

    How can I get into this? Maybe some advice? Please link to a forum where these issues can be discussed.

    1. Try to find the right config to enable related to I2C in "make menuconfig" and recompile the kernel to see if i2c-tools work (see )

      Please send a link to your blogpost if succesful :)

  5. Galland, I am trying to login with serial port of rk3188. Now I used "console=ttyFIQ0" in kernel boot command line and can get the login prompt. But I can't type anything. Is this a wire connection issue or software related issue?

  6. Replies
    1. Don't forget to blog about it when you achieve it