Preparation

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

Connections

Follow these steps to make the correct connections:

1) Connect the Tool Pin to the GPIOs, and check the Tx/Rx Pin once more to ensure that you have amde correct connections:

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

2) Insert the USB-end into your PC.

The connections should look like this:

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

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 finsh 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
robust
set file type bin
set file name lit
set rec pack 1000
set send pack 1000
set window 5
c

Run command kermit to launch C-kermit

Ensure that you have made the correct connections. If everyting 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.
----------------------------------------------------

1. If the treminal output contains this line, you might need to check the previous step Add Access Permission.

   /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, and then you’ll have access to U-boot.

3.If your terminal prints these

?SET SPEED has no effect without prior SET LINE
Sorry, you must SET LINE or SET HOST first
...

See Also

C-Kermit offical websit