Packet Radio: AX25, Direwolf and Linpac on a Raspberry Pi

I’ve been playing around trying to get a working config for using Direwolf as a soundcard modem for packet radio on the Raspberry Pi. I’ve played with getting ax25 and Direwolf running on Ubuntu (see here), and then I tried to copy across what I’d learnt to the Pi (running Raspbian).

The trouble with a lot of this stuff is there’s not much in the way of docs (although the Direwolf docs are really good), so when things don’t work you either start trying stuff randomly or just get stuck. Anyway, here’s the combination I have working:

  • Raspberry Pi (v1 model B) running Raspbian
  • RigBlaster connected via USB, connected to an Icom 880h
  • soundlevels at around 3/4 via alsamixer
  • Per ax25 on CentOS here, I used the ax25 sources from VE7FET’s github repo, compiled and installed

Most of my steps are the same as from my prior experience getting Direwolf and Linpac working on Ubuntu, so follow those steps if you’re looking to get setup, and then I’ve summarized the differences here.

The VE7FET source when you ‘sudo make install’ creates config files to /usr/local/etc/ax25 and not the default location of /etc/ax25. I’m not sure if Linpac likes this, so per a posting I found somewhere, the quick way to keep everyone happy is just create a symlink:

cd /etc/
sudo ln -s /usr/local/etc/ax25 .

Edit the axports file, add a line like:

1 KK6DCT-2 38400 253 2 2m packet

‘1’ is the portname

On the Pi I did run into the kissattach issue getting the ‘error setting line discipline’ error as described in the direwolf docs. Per the docs, I used the second of the workarounds:

sudo /usr/sbin/kissattach /dev/ptmx radio 44.56.4.118

then:

sudo mkiss /tmp/kisstnc /dev/pts/5

where the /dev/pts/5 value is returned from the kissattach step.

At this point I’m ready to go:

‘call 1 kberr’ opens a connection to my nearest node (using port 1)

And also Linpac starts up (with linpac -m), can can connect the same there with ‘:c kberr’

At some point I should probably walk through these steps with a fresh Raspbian install to confirm I didn’t change anything else along the way that was key to getting this to work, but I think this summarizes the key points.

A few other helpful points:

  • in the Mac Terminal app by default, the Alt key doesn’t work so can’t do a Alt-X to exit Linpac. There’s a tip here to enable the Option key as Alt so you can use this to cleanly exit Linpac.

Raspberry Pi Zero for $5

The Raspberry Pi at just $35 I think is one of the most amazing things that has arrived in recent years, bringing low cost computing to schools and hobbyists.

Today however, the Raspberry Pi Foundation has announced the Pi Zero … for $5. Incredible!

If you’re in the UK and can pick up a copy of The MagPi magazine, there’s a free Pi Zero taped to the front cover…

 

 

Changing display resolution on Rasbian

Settings such as HDMI video output are configured in the /boot/config.txt file – you can edit this on the Pi with ‘sudo nano /boot/config.txt’. If you need to edit on another machine, see details here.

This page lists available video modes. On my LG E2341 connected by HDMI, uncommenting and changing these two settings works to set the output to 1080p:

hdmi_group=1

hdmi_mode=16

 

 

Setting Raspberry Pi / Raspbian default locale and keyboard settings

Default locale and keyboard settings on the Raspberry Pi can be configured using raspi-config on Rasbian.

Select option 4 Internationalization, and select options to configure your locale, timezone and connected keyboard layout.

If you’ve installed Raspbian and kept the defaults you probably ended up with a UK keyboard layout, and if you have a US keyboard, you’re wondering why some of your keys are producing unexpected characters 🙂