Running an ax25 netrom node on a Raspberry Pi

I’ve played with Packet Radio using a Raspberry Pi a number of times in the past, and have a posted a number of posts – here’s some of my previous posts:

At one point I set up a Node.js app that used a library to read ax25 packets over Serial, and then Tweet received packets (here, here, and here). I ran this for a while but then took it down when I reused that Pi for another project.

A number of times I wondered what would it take to use this same approach with a client app directly interacting via ax25 packets to build an interactive app or game over Packet Radio. I did look into options for a while but didn’t get too far. I had noticed a couple of times that the node software or BBS software accessed via Packet could allow access to interact with apps running locally. Again, I looked into this for a while but didn’t get too far.

During some recent searching online, I wondered if anyone else had some something similar to this and set up access to a text based game like a text adventure, and of course they have, because why not? Richard Osgood has a fantastically good and well written article here walking through setting up ax25, and ax25 node and integrating access to Zork. If you’ve never done any Packet setup on the Pi before, this covers everything you need to get up and running.

From my previous setups I have already done ax25 and Direwolf configs before, so what I was more interested in what the delta between my previous previous steps and getting ax-25 node setup and able to interact with other apps.

I’ve summarized my steps here from the point of assuming you already have ax25 and Direwolf setup. If not you’ll need to go back to Richard’s original article and start from the beginning, or look at the links to my previous articles at the start of this post.

So, picking up from already having ax25 installed and configured and working with Direwolf:

Install ax25-node and telnet (for local testing):

sudo apt-get install ax25-node telnet

I already had ax25-tools and ax25-apps installed from my previous setup.

Configure nrports:

sudo nano /etc/ax25/nrports

Add 1 line:

netrom KK6DCT-6 #DAVBBS 255     Netrom node

-6 is my SSID for the netrom node, DAVBBS is my node alias

ax25d config:

sudo nano /etc/ax25/ax25d.conf

Add:

Add these 2 sections, you can delete or commented out the example configs in the file:

[KK6DCT-6 VIA 1]
NOCALL * * * * * * L
default * * * * * * - root /usr/sbin/ax25-node ax25-node

<netrom>
NOCALL * * * * * * L
default * * * * * * - root /usr/sbin/ax25-node ax25-node

The ‘VIA 1’ in the fist config is referring to the ‘1’ interface already defined in my /etc/ax25/axports.

Configure the node:

sudo nano /etc/ax25/node.conf

There’s a lot of defaults and examples in this file. I kept any timeout values unchanged, but changed:

HostName KK6DCT-6
NodeId   #DAVBBS:KK6DCT-6

Node permissions:

sudo nano /etc/ax25/node.perms

I kept :

# user type port passwd perms
kk6dct * * CHANGEPASSWORD 255

# Default permissions per connection type.
#
* ax25 * * 7
* netrom * * 7
* local * * 7
* ampr * * 7
* inet * * 7
* host * * 7

Change CHANGEPASSWORD for a password for local testing via telnet.

TODO – check whether I changed these defaults

nrbroadcast – in my default copy of the file there’s 2 default lines, one I’m assuming for port 1 and one for port 2. I’ve only configured port 1, so I deleted the second line:

sudo nano /etc/ax25/nrbroadcast
# /etc/ax25/nrbroadcast
#
# The format of this file is:
#
# ax25_name min_obs def_qual worst_qual verbose
#
1	5	192	100	0
#2	5	255	100	1

Start up netrom:

sudo nrattach netrom

if you get a “no such device” error, do a “sudo modprobe netrom” first.

nrattach: SIOCGIFFLAGS: No such device
nrattach: cannot find free NET/ROM device
$sudo modprobe netrom
$ sudo nrattach netrom
NET/ROM port netrom bound to device nr0

Configure telnet for testing:

sudo nano /etc/services

Add:

ax25-node       4444/tcp        # KK6DCT-6 node

This allows an incoming connection e.g. via telnet to get handled by ax25-node.

Configure ax25-node to start at boot:

sudo nano /etc/inetd.conf

Add:

ax25-node stream tcp nowait root /usr/sbin/ax25-node ax25-node

Note that this file also has a default line added for a bbs service over ax25, but this line has wait instead of nowait. I don’t know what this option does, but if you use wait instead of nowait you won’t get a connection to the node – don’t uncomment this line:

#:OTHER: Other services
#<off># bbs     stream  tcp     wait    root    /usr/sbin/ax25-node     ax25-no$

Restart inetd:

sudo service inetd restart

Now start up netromd and ax25d:

sudo netromd
sudo ax25d

Ready to go!

At this point I can telnet into my node locally, and also receive incoming connections over Packet.

I tested this locally with 2 packet stations:

  • Raspberry Pi set up as above, using a Signalink connected to a Wouxun KG-UV5D HT, and a Ed Fong rollup 2m/440cm antenna hanging against a window indoors.

With this radio on low power (1w) I can get to the local BERR37 node on 145.370MHz up on the hills near Lake Berryessa – in a straight line that’s roughly 20 miles from my location.

To test accessing the node running Zork and a command line weather forecast util called ansiweather I used:

  • AES PK232 accessed via a VT132 terminal card, connected to an Icom 880h and my regular 1/4 wave antenna in my attic.

Here’s accessing the node (KK6DCT-6) via the VT132 and PK232. What you’re looking at here is the VGA output from the VT132 terminal connected to the PK232 TNC:

  • c KK6DCT-6 : connect to the node
  • ? : list commands for the node – note ‘Weather’ and ‘Zork1’ in the list
  • w : run the weather command which calls answeather

Here’s Direwolf running on the Raspberry Pi. The ax25 startup steps are on the left (I didn’t get them setup to start on boot yet), and Direwolf receiving and sending on the right:

Here’s the hardware side of this Packet craziness on my desk. The Wouxun and Signalink on the right are connected to the Raspberry Pi which is out of the picture on the right. The AES PK232 at the bottom is connected to the Icom 880h on the right (the rest of the gear is not in use for this packet setup):

Sending Packet Radio beacons with ax25 ‘beacon’

The ax25 app ‘beacon’ does what it says, it sends beacon packets, by default every 30 mins, e.g.

beacon -c KK6DCT-6 1 "Hello from KK6DCT-6 node!"

By default the callsign will be what you’ve configured for your node/tnc, but you can change that with the -c param. The next param is the ax25 interface number from /etc/ax25/axports, followed by your beacon message.

Working Packet Radio with a VT132 and a AEA PK-232

I’ve posted before about using a VT132 terminal board to control a PK-232 packet TNC. Here’s a few more specific steps and commands.

On first startup after doing the * auto-baud detection, the first thing you’ll see is the “cmd” prompt. If this is your first time setting up, or if the internal battery is low and it’s not preserving your settings since last time, the first thing you’ll want to do from the cmd: prompt is set your callsign (set your own callsign here):

my KK6DCT
MYcall was PK232
MYcall now KK6DCT

If you’re working VHF packet, turn on VHF mode, with:

VHF ON

If it was off, now it’s on.

Set baud to 1200 for VHF packet:

HB 1200

Now enter D to disconnect, and we’re ready to send some packets. To re-enter this command mode, press Ctrl C.

By default the PK232 has a MPROTO value of OFF which doesn’t display any received packets other than those sent to your callsign. Set MPROTO ON and you’ll display other packets heard.

Additionally, the default value of MON as 4 will show some but not all packets. Set MON 6 to display all packets decoded. If you’re hearing other packets but they’re still not being decoded, enter WHYNOT ON to get an explanation.

At this point you’re ready to go. C NODENAME to connect to a nearby node!

Packet Radio via the International Space Station – March 2021

The Packet Radio service on the ISS has been out for a few months, but during an EVA yesterday a cable was replaced and the service is back up again for the first time today.

I used my regular 2m radio , an Icom 880h with my homebrew copper wire 2m groundplane antenna in the attic, and transmitted on full power (50w), hooked up to a laptop via a Rigblaster, running UZ7HO soundmodem for the packet radio modem, and used the UISS software to send the APRS packets.

The pass was only 57 degrees at the highest, so it wasn’t a particularly high pass. I don’t think I started to hear packets until it was a couple of mins towards the peak. I heard 6 other stations get digipeated by the ISS: KB6LTY, K6FVC, N6RSX, KG6LHW, W7OSG and AB7DY, and I got about 3 APRS transmission digipeated (my callsign is KK6DCT):

If you’re wondering what this is about I have a couple of other posts from when I tried to get this working a few years ago: