Sending Files Over Serial With Kermit

Introduction

I recently needed to send a binary FPGA image file from a Windows PC to a device running embedded Linux that only had a serial console access on a USB port. Fortunately, the device had kermit installed and I could use Tera Term to transfer the file.

Kermit is a file transfer/management protocol and a set of communications software tools. Kermit can be installed on Liunx using standard package repositories. Versions for Windows and most other platforms are available from http://www.kermitproject.org/current.html. Tera Term has kermit built in and can be downloaded from https://ttssh2.osdn.jp/index.html.en.

Running Kermit

Kermit is started on Linux by running

$ kermit

Once started kermit will output something similar to the following and enter the kermit prompt

C-Kermit 9.0.304 OPEN SOURCE: Dev.22, 1 May 2017, for Linux
 Copyright (C) 1985, 2017,
  Trustees of Columbia University in the City of New York.
Type ? or HELP for help.
(~/) C-Kermit>

Configure Serial Connection

To display the detected serial ports on the remote Linux machine run the dmesg command and search for serial ports:

$ dmesg | grep tty

In my case the USB console was \dev\ttyPS0.

The kermit console can then be used to configure the serial port at \dev\ttyPS0 and file settings:

(~/) C-Kermit> set line \dev\ttyPS0
(~/) C-Kermit> set carrier-watch off
(~/) C-Kermit> set speed 115200
(~/) C-Kermit> set parity none
(~/) C-Kermit> set stop-bits 1
(~/) C-Kermit> set flow-control none
(~/) C-Kermit> set file type bin

In my case the port is set to 115200 baud, 8 bits, no parity, 1 stop bit, no flow control and the file type is binary.

Now, to connect to the Windows host PC run

(~/) C-Kermit> connect

once connected prepare kermit to receive a file:

(~/) C-Kermit> receive
Return to your local Kermit and give a SEND command.

KERMIT READY TO RECEIVE...

Transfer File Using Tera Term

Open Tera Term and setup the serial connection Setup > Serial Port.... Use the same settings as the remote kermit session above. The relevant port can be found using the Windows Device Manager. To open the port click New open.

To start the file transfer click File > Transfer > Kermit > Send... and select and open the file you wish to send.

Ending a Kermit Session

Once the file transfer is complete, close the serial port and exit kermit:

(~/) C-Kermit> close
(~/) C-Kermit> exit

The default location for the transferred file is your home directory.

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