Using Minicom and a USB/Serial cable to talk to your KPC 3+

The first time I tried to communicate with my AVRs from a linux machine after passing out from college (where Windows and Bray's terminal were the order of the day), I wondered how do we do that here? The terminal in linux is this system's shell (or pseudo shell), but how do I talk to the device connected over a serial (or serial to USB) link? I then remembered the much scorned 'Minicom'. Pain to live with, but hard to live without.

a sudo apt-get install minicom does not take much brain.

But the next question was, how do I use this thing? This simple and short article from Linux Journal gives a quick start, at least I could bit-bang ( ;-) ) my AVR in less than 5 minutes after so many years.

Over the weekend, I was showing Linux and Packet radio and for some reason I could not talk to my TNC, a KPC 3+. It was at this point that I realized I had forgotten more about Linux (and minicom) than I had about the commands needed to control the TNC. So, in the interest of helping save you some time, here is a quick write up on using minicom with a USB/Serial adapter to talk to your TNC, specifically, a KPC.

Minicom is an old school program that is available for most of the distributions but may not be installed by default. The good news: it is in all the repositories, so you can pull it down and install it quickly.

It is a serial terminal program that runs from the command line, but can sometimes be a little fussy to get working, and I will admit that I have not used minicom with a USB/Serial converter.

First, you have to know what tty port your USB/Serial converter is
on. So, plug it in, give it a minute and then type at a console port:

dmesg | grep tty

You should get something like this back:


kg4giy@kauai:/$ dmesg | grep tty
[ 0.001982] console [tty0] enabled
[ 686.529224] usb 2-2: pl2303 converter now attached to ttyUSB0

In this case, the converter is attached to ttyUSB0, you when you
configure minicom, you want to use /dev/ttyUSB0 as the serial port
setting.

To start minicom then (assuming you have not configured it, but you
know the modem speed of the TNC) type:

$ sudo minicom -s

Note that minicom requires root privileges. You will be prompted for
your password.

Select "Serial port set up" from the list with the cursor keys and set
the serial device and the Bps/par/bits (8/N/1 and whatever the speed
of your TNC is). Press , Save setup as dfl to save your
settings and then select Exit to enter minicom.

Turn on the TNC. Press once or twice if you do not get the
TNC cmd: prompt and you should now have control of the TNC.

When you are done, A then Z will bring up the help menu and you
can exit by pressing Q or A Q to exit.

One thing to note. Minicom has a much smaller set of connection speeds. For overall interoperability, it is best to set the baud rate of your TNC to 9600, with 8-n-1 for parity. This will facilitate connectivity with a multitude of devices, including a simple VT220.

I hope this saves you all a few minutes!

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