Setup Serial Debugging Tool


  • You need a “Serial Debugging Tool”. In this guide, we will use a “USB to TTL Converter”.


Follow these steps to make the correct connections:

1) Connect the Tool Pins to the GPIOs, and check the Tx / Rx Pins once more to ensure that you’ve made correct connections:

  • Tool Pin GND: <—> Pin17 of VIMs’s GPIO
  • Tool Pin TXD: <—> Pin18 of VIMs’s GPIO (Linux_Rx)
  • Tool Pin RXD: <—> Pin19 of VIMs’s GPIO (Linux_Tx)
  • Tool Pin VCC: <—> Pin20 of VIMs’s GPIO

2) Insert the USB-end into your PC.

The connections should look like this:

Image of SerialConnections

Another photo for more details (VCC Pin is not necessary):

Image of SerialConnections

Setup Kermit Protocol(C-Kermit)

Install c-kermit:

$ sudo apt-get install ckermit

Add Access Permission:

$ sudo usermod -a -G dialout $(whoami)

Add the following contents into ~/.kermrc to finish the setup:

Use nano, $ nano ~/.kermrc to create a new .kermrc file. Then copy-paste the contents below.

set line /dev/ttyUSB0
set speed 115200
set carrier-watch off
set handshake none
set flow-control none
set file type bin
set file name lit
set rec pack 1000
set send pack 1000
set window 5

After you’re done copy-pasting, save and exit nano.

Run command kermit to launch C-Kermit

Ensure that you have made the correct connections. If everything went well, you’ll see the following:

$ kermit
Connecting to /dev/ttyUSB0, speed 115200
Escape character: Ctrl-\ (ASCII 28, FS): enabled
Type the escape character followed by C to get back,
or followed by ? to see other options.
TE: 116640


Tips (and booting into U-Boot):

  1. If the terminal output contains this line, you might need to type sudo kermit.

    /dev/ttyUSB0: Permission denied
  2. To access U-boot, leave your USB-Serial-Debug tool connected, then press the reset button on your device once. You should see some print-out on your terminal, then quickly press the space-bar or control-c to stop auto-boot. You will see the prompt kvim# when you’ve entered u-boot.

  3. Note that to see the standard “help” commands as listed in the U-Boot Usage Guide, you’ll need to first have a version of Android or Ubuntu installed in your VIM device, from our krescue images.

  4. You can use the U-Boot command line (kvim#), to change your VIM’s default boot logo.bmp, according to the guide, Boot Logo for U-Boot.

See Also: