Upgrading bootloader

WARNING !
You can brick your Carambola. There is no way out. Ensure power is rock solid and don't breath while not finished :)

New Carambola's are shipped with enabled "serial upgrade" bootloader. If you have purchased it earlier, for some reason you might need to have this feature enabled. There is how to do it.

Start Terminal and TFTP programs.
Download firmware image from here
Connect UART, LAN, and power (or POE) cables.
Power on your Carambola.
You should see menu like this:

Please choose the operation:
  1: Load system code to SDRAM via TFTP.  
  2: Load system code then write to Flash via TFTP. 
  3: Boot system code via Flash (default). 
  4: Enter boot command line interface. 
  9: Load Boot Loader code then write to Flash via TFTP.

Select <9>
Enter Carambola and TFTP server addresses
Enter bootloader file name you wish to upload and press enter. This is it. Now there is no way out. There are big chances for you to brick Carambola at this stage if you cut power or press any keys like CTRL+C.

9: System Load Boot Loader then write to Flash via TFTP. 
 Warning!! Erase Boot Loader in Flash then burn new one. Are you sure?(Y/N)
 Please Input new ones /or Ctrl-C to discard
      Input device IP (10.10.10.123) ==:192.168.101.223
      Input server IP (10.10.10.3) ==:192.168.101.52
      Input Uboot filename () ==:uboot_3_3_5.bin

After a while Carambola should reboot and previous boot menu should look like this:

Please choose the operation:  
  1: Load system code to SDRAM via TFTP.  
  2: Load system code t hen write to Flash via TFTP. 
  3: Boot system code via Flash (default). 
  4: Entr boot command line interface. 
  7: Load Boot Loader code then write to Flash via Serial.  
  9: Load Boot Loader code then write to Flash via TFTP.

Congratulations. You have succeeded upgrading bootloader.