Online Amateur Radio Community Wiki

This page documents how I set up my Raspberry Pi running Raspbian Lite (32 bit).

My setup consists of:

• Raspberry Pi 4b
• CG Antenna 2000 Radio Interface
• Behringer UMC202HD Audio Interface
• Tait 2010 VHF Radio
• ICOM IC7300 HF Radio

sudo apt install libax25 ax25-apps ax25-tools socat direwolf

Notes:

• make absolutely certain that you are using a 32bit kernel if you have 32bit user binaries. I somehow ended up with a 64bit kernel and things broke in very subtle ways. Check that uname -m returns armv7l if you installed a 32bit OS!
• you may need to use api-update to get the latest series 6 kernel

I use Direwolf to run the two radios. Here is my Direwolf config:

ADEVICE plughw:1,0
ACHANNELS 1

ADEVICE1 plughw:4,0
ACHANNELS 1

CHANNEL 0
MYCALL M0GZP
MODEM 1200
PTT /dev/ttyUSB0 RTS

CHANNEL 2
MYCALL M0GZP-1
MODEM 300 7@30 E
PTT RIG 3073 /dev/ttyUSB1 
IL2PTX 

AGWPORT 0
KISSPORT 8001 0
KISSPORT 8002 2

This sets up two channels:

• CHANNEL 0 talks to sound card plughw:1,0 (which is the UMC202HD) and does PTT on /dev/ttyUSB0 (which is the CG Antenna 2000)
• CHANNEL 1 talks to sound card plughw:4,0 (which is the 7300) and does PTT on /dev/ttyUSB1 (which is the 7300)

It also disables AGW, and sets up two KISS listeners on port 8001 (assigned to channel 0) and 8002 (assigned to channel 2)

The config files are all in /etc/ax25. Here is what I set up for the three key files:

This file sets up two AX.25 ports, one for VHF and one for HF

v144    M0GZP-1         19200   236     4       144.375 Mhz 1k2bps
HF      M0GZP-2         19200   236     4       HF 300bps

This file sets up a NET/ROM port aliased as GZPNOD

netrom  M0GZP-7 GZPNOD  236     Linux Switch Port

This file configures how our AX.25 ports will broadcast NET/ROM nodes. My VHF node sets all seen nodes to a default quality of 220, and will broadcast any node with a minimum quality of 200. The HF node on the other hand sets all nodes to a default quality of 199 (so as not to advertise HF nodes over VHF), and will broadcast nodes with a minimum quality of 199.

v144    5       220     200     1
HF      5       199     199     1

I wrote some scripts to start everything up.

This script will:

• Create two socat pseudo-tty interfaces, one to each of the network KISS ports
• Use kissattach to attach these interfaces to kernel ax.25 network interfaces
• Load the netrom module and attach it to the port defined in nrports
• Run the netrom userspace daemon which handles the netrom broadcasts

#!/bin/bash
echo -n Creating socat sockets...
socat pty,echo=0,link=/tmp/kiss8001,wait-slave tcp:127.0.0.1:8001 &
socat pty,echo=0,link=/tmp/kiss8002,wait-slave tcp:127.0.0.1:8002 &
sleep 1
echo Done
echo -n Attaching KISS interfaces for direwolf...
kissattach `ls -l /tmp/kiss8001 | awk '{ print $11 }'` v144
sleep 1
kissattach `ls -l /tmp/kiss8002 | awk '{ print $11 }'` HF
sleep 1
echo Done
echo -n 'Bringing up NET/ROM runtime...'
modprobe netrom
nrattach netrom
netromd -i -l -d
echo -n Restoring node tables...
[ -x /etc/ax25/nodesave.sh ] && /etc/ax25/nodesave.sh
echo Done

This script does the opposite to startRadio, killing the processes and taking down the interfaces

#!/bin/bash
echo Saving node tables...
/usr/sbin/nodesave > /etc/ax25/nodesave.sh && chmod 755 /etc/ax25/nodesave.sh
echo Killing all kissattach processes
killall kissattach
echo Killing all socat processes in case they do not end cleanly
killall socat
echo Killing the netromd process
killall netromd
echo Taking down the netrom interface
ifconfig nr0 down
echo Removing kernel modules
rmmod netrom
rmmod mkiss
rmmod ax25
echo Taking down the AX.25 interfaces
ifconfig ax0 > /dev/null 2>&1 && ifconfig ax0 down
ifconfig ax1 > /dev/null 2>&1 && ifconfig ax1 down
echo Done

This script registers the ax25 service with systemd

[Unit]
Description=Start up radio processes

[Service]
Type=oneshot
ExecStart=/usr/sbin/startRadio.sh
ExecStop=/usr/sbin/stopRadio.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

To start things up, use systemctl start – then use status to see how it went:

szymon@radio:~ $ sudo systemctl start ax25
szymon@radio:~ $ sudo systemctl status ax25
● ax25.service - Start up radio processes
     Loaded: loaded (/lib/systemd/system/ax25.service; disabled; vendor preset: enabled)
     Active: active (exited) since Wed 2023-04-12 22:16:27 BST; 4s ago
    Process: 2476 ExecStart=/usr/sbin/startRadio.sh (code=exited, status=0/SUCCESS)
   Main PID: 2476 (code=exited, status=0/SUCCESS)
      Tasks: 5 (limit: 4915)
        CPU: 151ms
     CGroup: /system.slice/ax25.service
             ├─2477 socat pty,echo=0,link=/tmp/kiss8001,wait-slave tcp:127.0.0.1:8001
             ├─2478 socat pty,echo=0,link=/tmp/kiss8002,wait-slave tcp:127.0.0.1:8002
             ├─2486 kissattach /dev/pts/4 v144
             ├─2501 kissattach /dev/pts/2 HF
             └─2519 netromd -i -l -d

Apr 12 22:16:25 radio startRadio.sh[2483]: AX.25 port v144 bound to device ax0
Apr 12 22:16:25 radio startRadio.sh[2486]: AX.25 port v144 bound to device ax0
Apr 12 22:16:26 radio startRadio.sh[2499]: AX.25 port HF bound to device ax1
Apr 12 22:16:26 radio startRadio.sh[2501]: AX.25 port HF bound to device ax1
Apr 12 22:16:27 radio startRadio.sh[2476]: Done
Apr 12 22:16:27 radio startRadio.sh[2476]: Bringing up NET/ROM runtime...
Apr 12 22:16:27 radio startRadio.sh[2512]: NET/ROM port netrom bound to device nr0
Apr 12 22:16:27 radio netromd[2519]: starting
Apr 12 22:16:27 radio startRadio.sh[2476]: Restoring node tables...Done
Apr 12 22:16:27 radio systemd[1]: Finished Start up radio processes.
szymon@radio:~ $ 

You will see some new network interfaces on ifconfig (I've removed my normal interfaces):

ax0: flags=67<UP,BROADCAST,RUNNING>  mtu 236
        ax25 M0GZP-1  txqueuelen 10  (AMPR AX.25)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2  bytes 77 (77.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ax1: flags=67<UP,BROADCAST,RUNNING>  mtu 236
        ax25 M0GZP-2  txqueuelen 10  (AMPR AX.25)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2  bytes 77 (77.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

nr0: flags=193<UP,RUNNING,NOARP>  mtu 236
        netrom M0GZP-7  txqueuelen 1000  (AMPR NET/ROM)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

You can now use axcall to contact another node, axlisten to monitor traffic, etc.