Using an actual VT100 terminal with a Dell server

[Dave Burton]

I have an original, 41yo DEC VT100 terminal. I noticed that Dell R630 & R640 servers have 9-pin serial ports, and from the documentation it seems that the serial port can be used for server console access (BIOS etc.), and it can be configured for VT100/VT220 emulation. So, I thought, wouldn't it be fun to use a real  VT100 terminal to manage a modern Dell server?

So I lugged the old VT100 upstairs (I'd forgotten how heavy those things are!), vacuumed the dust out, and plugged it in.

It fired right up. I set it for 19,200 bps for both Tx and Rx (which is as fast as it will go). I found an old 9-pin to 25-pin adapter, connected the VT-100 to an R640's serial port, and... nothing.

I've tried a lot of different "Serial Communication" settings in BIOS. I set the "Remote Terminal Type" to VT100/VT200. I set the "Failsafe Baud Rate" to 19200. I tried various "Console redirection" settings. I tried it with and without a "null modem" crossover connector.

Still, I get nothing displayed on the VT100, and no response to VT-100 keyboard presses.

Does anyone know what I'm doing wrong?

Does the R640 use hardware flow control? (RTS/CTS or DTR/DSR?) Does it require 7-bit or 8-bit characters, with or without parity? Is its VT100/VT200 "remote terminal type" actually compatible with real VT100 & VT200 terminals?

 

[saivert]

Do you mean the console redirection feature that some BIOS has where you can see the bios menus over a serial connection?
Make sure the VT100 is set to the same baud rate, stop bits, and so on. To be safe try with 9600 baud rate first.

When I used serial connection as very cheap out of band management of a server 10 years ago I basically could only control early boot up (GRUB + Linux had serial console enabled) but BIOS didn't work. I connected a USB to RS-232 adapter to an Asus router that I run minicom on so that I could remotely log into my router over SSH and then from there connect to server over serial connection in order to reconfigure networking etc. without getting locked out.

 

[unwind-protect]

Do you really want to mess around in the BIOS with the vt100?

Linux and FreeBSD have their own gettys to have you log in from the terminal. You don't need BIOS support for that.

 

[Dave Burton]

Yes, salvert. It appears that all the R640's configuration features, including BIOS, should be accessible via a serial console connection.

With some of the "console redirection" settings I tried, I could see text-only menus on the attached KVM crash cart screen, like these:

Connecting Dell EMC PowerEdge servers using serial port | Management Networks for Dell EMC Networking Configuration Guide | Dell Technologies Info Hub

There are three types of management networks that are widely used with Dell EMC networked devices. This document provides the pros and cons of each management network type, and assists you in selecting one or more methods to suit your needs.

infohub.delltechnologies.com

Those menus are obviously intended for display on a serial terminal or serial terminal emulator, but I could never get anything to show up on the VT100.

The VT100, itself, can be set to 7 or 8 data bits, and to even, odd or no parity. But I don't know what the R640 expects.

I only tried 19,200 baud, but I'll try 9600.

It doesn't really matter, anyhow. I don't NEED it to work, I just thought it'd be cool.

 

[NablaSquaredG]

The VT100, itself, can be set to 7 or 8 data bits, and to even, odd or no parity. But I don't know what the R640 expects.

I only tried 19,200 baud, but I'll try 9600.

Usual settings are 9600 8N1

 

[Dave Burton]

Thanks, Nabla. I've set the VT100 Tx & Rx speeds, and also the R640 "Failsafe Baud Rate," to 9600. The VT100 was already set to 8 data bits and no parity. Number of stop bits is not configurable, but my vague memory is that it was only at 110 baud that 2 stop bits were commonly used, so the VT100 is probably using just 1.

It still isn't working.

 

[UhClem]

...
So I lugged the old VT100 upstairs (I'd forgotten how heavy those things are!), vacuumed the dust out, and plugged it in.

It fired right up. ...

Meaning? ... no smoke, & blinking cursor? (ie, it seems to power on OK)

... Still, I get nothing displayed on the VT100, and no response to VT-100 keyboard presses.

But, has that vt100 demonstrated transmit/receive functionality on any serial line recently?? (ie, Troubleshooting 101)

 

[Dave Burton]

But, has that vt100 demonstrated transmit/receive functionality on any serial line recently?? (ie, Troubleshooting 101)

Yes, with a loopback connection (wire between Tx and Rx) it echoes typed characters to the screen.

 

[saivert]

I once made a dumb SSH terminal using an old 14 inch CRT TV and a raspberry pi.
The resolution of such TVs are pretty much crap for anything but a text mode terminal.

It doesn't have the same coolness of an actual DEC VT100 though but it was fun enough for a time.

Though I'm curious if you managed to get it to display a Linux kernel console (getty) yet? It may be that the BIOS console redirection isn't working.

 

[Dave Burton]

I haven't tried that, saivert.

 

[nexox]

I find the easiest way to experiment with serial consoles is from within Linux, using stty to change settings and then just echo foo > /dev/ttyS0 (or whichever serial device) to see how it works. After you get the settings nailed down then it's pretty simple to set up a getty or add a couple console= arguments to the bootloader, I usually deal with the BIOS console redirection last because it takes the most time to adjust and test.

 

[x041]

Very curious to see how this turns out