Troubleshooting serial terminal connections (VT Serial Terminal, VT132, Packet Radio TNCs)

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!

Sun Ultra 60 serial console login with a VT132

I recently assembled a VT132 and have been connecting it to various things to enjoy some serial terminal goodness.

I’ve tried a number of serial cables and serial terminal programs on my Atari ST to get a serial connection to my Sun Ultra 60 but never managed to get it to work. I didn’t know if this was due to my serial cable or something else. I bought and assembled the VT121 as a VT100 compatible serial terminal to have a better attempt at connecting to some of the devices I have around that support serial connections.

On the VT132 there are jumper pins to switch between a straight though connection or a crossover connection. Through trial and error I found I needed to put the jumpers on 1-3 and 2-4 for the cross over connection and this worked with the Sun Ultra.

I don’t have a pic of the pins in this configuration, this is the section in the docs, and here’s the pin layout next to the voltage regulator for reference (center of the photo):

Pins 1 2 3 4 are on the right. Here’s the pins in the straight through config 1-2 and 3-4, the two jumpers on the right need to be switched to the other 1-3 and 2-4 configuration to work with the Sun Ultra:

There’s two serial connectors on the Sun Ultra 60, note that the DB25 at the top is a parallel connector. Serial A and B are beneath the keyboard connector:

Here’s some useful info on configuring Serial console connections to Sun hardware here. Typically on Sun Sparc systems, if you disconnect the keyboard and have a terminal connected to Serial A when you boot, the boot messages are redirected to the serial terminal instead of the video output. This is useful if you need to run diags on a machine, but it’s also fun to boot the machine up and logon from a serial console. Here’s what the console boot messages look like on my Ultra 60:

At this point I could successfully logon via the console. As I was looking into getting this working I took some notes as I was working on this. I’ll include them here for future reference in case they’re useful.

Other useful notes:

/etc/remote has section for enabling hardwire tip via /dev/term/a|b

See also here https://docs.oracle.com/cd/E19455-01/806-1377-10/tipapp.html talks about /etc/ttytab to enable logins

To enable a logon prompt via Serial A or B after booting, and with keyboard connected:

From here: https://docs.oracle.com/cd/E19253-01/817-0403/modsafapp-84569/index.html

sacadm -a -p mbmon -t ttymon -c /usr/lib/saf/ttymon -v `ttyadm -V` -y "TTY Ports a & b"

cat /dev/term/a shows keyboard entry from my VT132 terminal when I press enter, so I know input is reaching the port.

With my serial cable, I needed to set the straight through vs crossover jumpers on the VT132 to the crossover position get any output to appear on the terminal.

Set terminal to 9600 8N1.l

VT132 Using the AT Modem over WiFi

The VT132 includes a telnet/WiFi modem that supports AT commands to ‘dial’ online sites, such as BBSes that are accessible using telnet.

To connect to the modem, use the Alt-F1 menu and enable the ‘Enable modem locally’ option:

Useful commands:

AT$ – lists commands and help:

AT+W? – displays current WiFi status

AT+W=ssid,password : connect to WiFi ssid with password

AT+W$ – shows IP address when connected to WiFi:

AT+W+ : reconnects to WiFi using params last used and stored

AT+W- : disconnects from WiFi

Testing dialing up Retro Battlestations BBS: ATDbbs.fozztexx.com

Since VT132 also supports ANSI escape sequences, dialing up Blackflag BBS has some awesome ANSI graphics: ATDblackflag.acid.org :

Using a VT132 for Packet Radio

I have an AEA PK-232 that I picked up a couple of years ago at my Amateur Radio club’s White Elephant sale for a few bucks. With the VT132 that I just recently built, it works as an excellent terminal client to the PK-232.

To connect, set baud rate in the VT132 to 1200 8N1. Connect with a null modem cable. Power on the PK-232 and you should see:

Press type a star (*) for auto-baud routine.

Press * and then you should see the AEA PK-232 startup copyright message.

To get a cmd: prompt to enter commands, press Ctrl-C.

I’ve attached my 2m radio with the audio in so far, and here’s a pic while decoding some APRS messages:

Next I need to make a custom cable to connect to my Icom’s data port, and then I should be all set to work some packet.