Grub: memdisk, at_keyboard

[dernsen]

   Hi,
   I want setup the same keyboard layout (non  US layout) for grub-shell
   as in the booted debian_64 (uefi) system.
   So i created standalone grub-image with a memdisk for kbd-layout, a
   embeded  grub.cfg with "terminal_input at_keyboard".
   This works very good for my notebook, so I transferred it to my
   workstation with usb-keyboard.
   The keyboard works in uefi bootmenu, etc., but after grub takes over it
   is not working anymore (i have to push the power button). If I remove
   the "terminal_input at_keyboard" line of embedded grub.cfg usb-keyboard
   works but without the embedded keyboard layout.
   I tried to use the usb_keyboard grub-module, etc. , the outcome is
   always the same:
   - If the keyboard works, then just with the standard keyboard layout or
   it is not working anymore.
   How to get the embedded keyboard layout and the usb-keyboard working at
   the same time?