Get the keycode of a key, from a custom made keyboard

Question

I'm trying to transform a Minitel to a computer with a Raspberry Pi.

This is a minitel:

So I soldered the matrix of the minitel keyboard to a usb keyboard pcb, like this:

Everything is working ok, I recieve some keys from my custom keyboard. I just need to remap the keys appropriately.

So I'm trying to create a program that will ask me to press a and trap the corresponding keycode, and then with all keys of my custom keyboard, to finaly produce a xmodmap file.

The only problem I have is that I can't figure out on how can I get that keycode (and only that!). I tried xev but there's too much data displayed to filter it out.

I know I could track all the keycodes by hand, but I'll transform 10 Minitels, so I would prefer a quicker way!

Answer 1

I assume you're trying to do this in shell or similar (else, you'd just use the X libraries directly). If so, you may find xinput --test «device-name» much easier to parse.

Unfortunately, it really isn't shell-scripting friendly. But you can make it work with stdbuf. It runs until you kill it, but your shell script could pipe it to read.

So, you can do something like this:

stty -echo
stdbuf -oL xinput test 'AT Translated Set 2 keyboard' \
    | perl -nE 'BEGIN {$| = 1} m/^key press\s+(\d+)/ and say $1' \
    | for key in q w e r t y; do
         echo -n "Please press $key: "
         read -r keycode
         echo "key $key = $keycode"
    done
stty echo

You will need to use the correct keyboard name in place of "AT Translated Set 2 keyboard". You can find it with xinput list:

anthony@Zia:~$ xinput list
⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ Logitech USB-PS/2 Optical Mouse           id=8    [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Power Button                              id=6    [slave  keyboard (3)]
    ↳ Power Button                              id=7    [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard              id=9    [slave  keyboard (3)]

Unfortunately, you have to use a specific device—you can't use the core keyboard.

(Also, you'll need to find a way to kill the xinput in the above, or just content yourself to hit Control-C when you've entered all the keys. And you'll probably want to list more keys than qwerty.)