Minitel

1.1 Introduction

1.1.1 Contributing

Found an error or have a suggestion? Please open an issue on GitHub (github.com/pojntfx/minitel):

1.1.2 License

This document and included source code is Free Culture/Free Software.

Minitel (c) 2021 Felicitas Pojtinger

SPDX-License-Identifier: AGPL-3.0

1.2 Compatible Minitels

Your Minitel needs to have a Funz or Fnct key and the DIN-5 port at the back side. This includes the following Minitels:

• Minitel 1B
• Minitel 2
• Alcatel ADF 258

1.3 Minitel DIN-5 to USB/RS232/Serial Adapter

To build the adapter to connect the Minitel to a PC, you need the following (cheap) components:

• 220 kΩ resistor
• 22 kΩ resistor
• 10 kΩ resistor
• 2N2222 transistor
• Male DIN-5 plug
• PL2303HX USB to UART TTL converter

You will need to check the pinout of the DIN-5 plug/cable; in my case, the following mapping is present:

Connect like so:

In my case, the breadboard prototype ended up looking like this:

I got this layout from Pila’s blog.

1.4 Minitel Shortcuts

Minitel terminals show the integrated phonebook by default; for them to be usable serial terminals, use the following shortcuts:

French Minitel 1B/2:

1. Fnct + T A: Enables ASCII mode
2. Fnct + T E: Disables local echo
3. Fnct + P 4: Sets baud rate to 4800 Baud (the maximum)

More info can be found on Pila’s blog.

Italian Minitel (Alcatel ADF 258):

1. Funz + Mem: Switches to terminal mode
2. Funz + M A: Enables ASCII mode
3. Funz + M E: Disables local echo
4. Funz + B 4: Sets baud rate to 4800 Baud (the maximum)

More info can be found on Retronomicon.

1.5 Testing the Adapter

First, plug the PL2303HX into a USB port on your PC, then run the following:

$ sudo stty -F /dev/ttyUSB0 4800 istrip cs7 parenb -parodd brkint ignpar icrnl ixon ixany opost onlcr cread hupcl isig icanon echo echoe echok

This will initialize the terminal. Now, set up the Minitel using the shortcuts, and try to display something on it:

$ echo 'Hello, Minitel!_' | sudo tee /dev/ttyUSB0

If the _ did not print correctly, run the following and try again:

$ echo 'ǎ' | sudo tee /dev/ttyUSB0 # Fixes # and _ etc.

You may use Minicom for further debugging: Start it using sudo minicom -s -D /dev/ttyUSB0 and use 4800 Baud, 7 data bits, even parity bit, 1 stop bit and disable hardware flow control.

1.6 Setting up the Keymap

Alexandre Montaron has worked on improved support for the Minitel on Linux by providing a terminfo file; to get and use it, run the following:

$ curl -L -o /tmp/mntl.ti http://canal.chez.com/mntl.ti
$ tic /tmp/mntl.ti -o /etc/terminfo

You can also find a mirror on GitHub Gist.

1.7 Setting up agetty

Using getty, or agetty in our case, it is possible to log into your PC using the Minitel. Exact setup instructions depend on your distribution, but for Fedora 35 the following works; be sure to set up the Minitel using the shortcuts beforehand:

$ sudo tee /usr/lib/systemd/system/minitel-getty@.service <<'EOT'
#  SPDX-License-Identifier: LGPL-2.1-or-later
#
#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.

[Unit]
Description=Serial Getty on %I
Documentation=man:agetty(8) man:systemd-getty-generator(8)
Documentation=http://0pointer.de/blog/projects/serial-console.html
BindsTo=dev-%i.device
After=dev-%i.device systemd-user-sessions.service plymouth-quit-wait.service getty-pre.target
After=rc-local.service

# If additional gettys are spawned during boot then we should make
# sure that this is synchronized before getty.target, even though
# getty.target didn't actually pull it in.
Before=getty.target
IgnoreOnIsolate=yes

# IgnoreOnIsolate causes issues with sulogin, if someone isolates
# rescue.target or starts rescue.service from multi-user.target or
# graphical.target.
Conflicts=rescue.service
Before=rescue.service

[Service]
# The '-o' option value tells agetty to replace 'login' arguments with an
# option to preserve environment (-p), followed by '--' for safety, and then
# the entered username.
ExecStart=/usr/bin/sh -c "chcon -t tty_device_t /dev/%I && sudo stty -F /dev//%I 4800 istrip cs7 parenb -parodd brkint ignpar icrnl ixon ixany opost onlcr cread hupcl isig icanon echo echoe echok && /sbin/agetty -o '-p -- \\u' -c %I 4800 m1b-x80 $TERM"
Type=idle
Restart=always
UtmpIdentifier=%I
TTYPath=/dev/%I
TTYReset=yes
TTYVHangup=yes
IgnoreSIGPIPE=no
SendSIGHUP=yes

[Install]
WantedBy=getty.target
EOT
$ sudo systemctl daemon-reload
$ sudo systemctl enable --now minitel-getty@ttyUSB0

You should now get a login prompt (Note the # where there should be a _):

You can show the login prompt again at a later time using the following:

$ sudo systemctl restart minitel-getty@ttyUSB0

After logging in, you should get a fully-featured shell:

We’ll fix the #/_ characters next.

1.8 Setting up tmux

tmux makes using the Minitel much more enjoyable by providing support for panes and much more. You can use it by running:

$ tmux

It should look like this:

To get started, I recommend taking a look at the Tmux cheatsheet.

To fix the #/_ characters and enable easy resetting when turning the Minitel on/off, run the following:

$ echo "bind-key r run-shell \"echo 'ǎ'; reset; echo 'Terminal has been reset, press q to close'\"" >>~/.tmux.conf

This will add a new command, Ctrl + b r, which will reset the terminal and fix the character set:

This now allows running complex software, like Vim, Links, Lynx and cmus: