I’ve been on a serial terminal kick the last few months. I think it started when I picked up a used Sun Ultra 60 and found out you could boot with a serial terminal to diagnose boot issues, and/or logon via a serial terminal. I built a VT132 kit and this has worked well using a regular VGA monitor and USB keyboard, but one thing lead to another and I started shopping ebay for a real DEC VT terminal. These are getting harder to find in working condition and it seems the prices are going up to pretty crazy levels. You can easily get one around $200 to $300, but if you shop around you should be able to get one around $100.
I’ve been able to connect the VT132 to anything so far and get it to work. There are a couple of jumpers on the board to select a straight through or crossover cable connection, if one doesn’t work change it to the other and it will connect. I’ve used it so far to connect to a AEA PK-232 Amateur Radio packet TNC, my Ultra 60, and a PC running Ubuntu.
The VT terminal on the other hand is more tricky. It will connect to the PK-232 and the wifi modem on the VT132, but I have not been able to successfully connect it to do a serial terminal logon to a Raspberry Pi (this was my main goal), or another PC yet.
My suspicion is that the 2 serial cables I have that I’ve been using interchangeably depending on what I’ve connecting too just based on the connectors are not the same. One has DB25 to DB25, the other has DB9 to DB25, so I’ve been picking the one that connects between the two devices. I’ve assumed these are both null modem cables, but I think one is straight through, and I don’t know which is which. I need to test them with a meter to find out.
I also thought the USB to serial connector that I was using on the Raspberry Pi was not working (it was a FTDI chip) so I bought another one using the Prolific chip, and that didn’t work either connecting from the VT Terminal, but it did from the VT132, so I think this is more to do with the serial cable than the Serial USB adapter. I think the clue was that from the VT132 it only worked when I switched the straightthrough to crossover jumpers to crossover, actually the same setting that works with the Ultra 60 too (but not the PK-232).
My next steps are to create a table of all the combinations that work vs don’t work. I also need to test the cables to find out if one is a straight through vs the other being a crossover cable. I think assuming they were the same is not true and this is causing the confusion. I will keep you updated on my findings!
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.
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
sudo nano /etc/ax25/ax25d.conf
Add these 2 sections, you can delete or commented out the example configs in the file:
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:
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):
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.
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):
MYcall was PK232
MYcall now KK6DCT
If you’re working VHF packet, turn on VHF mode, with:
If it was off, now it’s on.
Set baud to 1200 for VHF packet:
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!