09-06-2016
Quote:
Originally Posted by
bakunin
If i remember correctly the original PC keyboard was built on the Intel MCS-48 microcontroller, namely the 8042, all PC hardware still reflects that. The mcirocontroller sends so-called "make-" and "break-codes" to the main computer, which basically reflect pressing and releasing a key. Scancodes tell which key exactly was pressed (at this level is i.e. possible to separate the left from the right SHIFT key being pressed, etc.)
In the original design (but i have long since stopped to update my PC hardware knowledge) it used not only the BIOS-interrupt 09h, it also controlled the A20 gate, which was done because of a bug in the 80286 design (it couldn't get back from protected to real mode without a reboot).
I hope this helps.
bakunin
See here:-
Usb_kb-io.
However we are not talking BIOS interrupts which are immaterial in this thread but HID USB protocols, disabling a USB port to re-enable it again, but, redirected to a background process. Not as easy task for the big guns let alone amateurs like me.
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LEARN ABOUT X11R4
showkey
SHOWKEY(1) General Commands Manual SHOWKEY(1)
NAME
showkey - examine the codes sent by the keyboard
SYNOPSIS
showkey [-h|--help] [-a|--ascii] [-s|--scancodes] [-k|--keycodes] [-V|--version]
DESCRIPTION
showkey prints to standard output either the scan codes or the keycode or the `ascii' code of each key pressed. In the first two modes the
program runs until 10 seconds have elapsed since the last key press or release event, or until it receives a suitable signal, like SIGTERM,
from another process. In `ascii' mode the program terminates when the user types ^D.
When in scancode dump mode, showkey prints in hexadecimal format each byte received from the keyboard to the standard output. A new line is
printed when an interval of about 0.1 seconds occurs between the bytes received, or when the internal receive buffer fills up. This can be
used to determine roughly, what byte sequences the keyboard sends at once on a given key press. The scan code dumping mode is primarily
intended for debugging the keyboard driver or other low level interfaces. As such it shouldn't be of much interest to the regular end-user.
However, some modern keyboards have keys or buttons that produce scancodes to which the kernel does not associate a keycode, and, after
finding out what these are, the user can assign keycodes with setkeycodes(8).
When in the default keycode dump mode, showkey prints to the standard output the keycode number or each key pressed or released. The kind
of the event, press or release, is also reported. Keycodes are numbers assigned by the kernel to each individual physical key. Every key
has always only one associated keycode number, whether the keyboard sends single or multiple scan codes when pressing it. Using showkey in
this mode, you can find out what numbers to use in your personalized keymap files.
When in `ascii' dump mode, showkey prints to the standard output the decimal, octal, and hexadecimal value(s) of the key pressed, according
to he present keymap.
OPTIONS
-h --help
showkey prints to the standard error output its version number, a compile option and a short usage message, then exits.
-s --scancodes
Starts showkey in scan code dump mode.
-k --keycodes
Starts showkey in keycode dump mode. This is the default, when no command line options are present.
-a --ascii
Starts showkey in `ascii' dump mode.
-V --version
showkey prints version number and exits.
2.6 KERNELS
In 2.6 kernels key codes lie in the range 1-255, instead of 1-127. Key codes larger than 127 are returned as three bytes of which the low
order 7 bits are: zero, bits 13-7, and bits 6-0 of the key code. The high order bits are: 0/1 for make/break, 1, 1.
In 2.6 kernels raw mode, or scancode mode, is not very raw at all. Scan codes are first translated to key codes, and when scancodes are
desired, the key codes are translated back. Various transformations are involved, and there is no guarantee at all that the final result
corresponds to what the keyboard hardware did send. So, if you want to know the scan codes sent by various keys it is better to boot a 2.4
kernel. Since 2.6.9 there also is the boot option atkbd.softraw=0 that tells the 2.6 kernel to return the actual scan codes.
SEE ALSO
loadkeys(1), dumpkeys(1), keymaps(5), setkeycodes(8)
1 Feb 1998 SHOWKEY(1)